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Merge branches 'boards' and 'fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/hskinnemoen/avr32-2.6

This commit is contained in:
Haavard Skinnemoen 2008-10-23 15:24:10 +02:00
parent 72a1419a9d e82c6106b0
commit d9214556b1
7303 changed files with 578203 additions and 188702 deletions
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1
.mailmap
View File

@ -66,6 +66,7 @@ Kenneth W Chen <kenneth.w.chen@intel.com>
Koushik <raghavendra.koushik@neterion.com>
Leonid I Ananiev <leonid.i.ananiev@intel.com>
Linas Vepstas <linas@austin.ibm.com>
Mark Brown <broonie@sirena.org.uk>
Matthieu CASTET <castet.matthieu@free.fr>
Michael Buesch <mb@bu3sch.de>
Michael Buesch <mbuesch@freenet.de>

12
CREDITS
View File

@ -1653,14 +1653,14 @@ S: Chapel Hill, North Carolina 27514-4818
S: USA
N: Dave Jones
E: davej@codemonkey.org.uk
E: davej@redhat.com
W: http://www.codemonkey.org.uk
D: x86 errata/setup maintenance.
D: AGPGART driver.
D: Assorted VIA x86 support.
D: 2.5 AGPGART overhaul.
D: CPUFREQ maintenance.
D: Backport/Forwardport merge monkey.
D: Various Janitor work.
S: United Kingdom
D: Fedora kernel maintainence.
D: Misc/Other.
S: 314 Littleton Rd, Westford, MA 01886, USA
N: Martin Josfsson
E: gandalf@wlug.westbo.se

7
Documentation/00-INDEX
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@ -21,6 +21,9 @@ Changes
- list of changes that break older software packages.
CodingStyle
- how the boss likes the C code in the kernel to look.
development-process/
- An extended tutorial on how to work with the kernel development
process.
DMA-API.txt
- DMA API, pci_ API & extensions for non-consistent memory machines.
DMA-ISA-LPC.txt
@ -159,8 +162,6 @@ hayes-esp.txt
- info on using the Hayes ESP serial driver.
highuid.txt
- notes on the change from 16 bit to 32 bit user/group IDs.
hpet.txt
- High Precision Event Timer Driver for Linux.
timers/
- info on the timer related topics
hw_random.txt
@ -251,8 +252,6 @@ mono.txt
- how to execute Mono-based .NET binaries with the help of BINFMT_MISC.
moxa-smartio
- file with info on installing/using Moxa multiport serial driver.
mtrr.txt
- how to use PPro Memory Type Range Registers to increase performance.
mutex-design.txt
- info on the generic mutex subsystem.
namespaces/

62
Documentation/ABI/stable/sysfs-driver-usb-usbtmc Normal file
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@ -0,0 +1,62 @@
What: /sys/bus/usb/drivers/usbtmc/devices/*/interface_capabilities
What: /sys/bus/usb/drivers/usbtmc/devices/*/device_capabilities
Date: August 2008
Contact: Greg Kroah-Hartman <gregkh@suse.de>
Description:
These files show the various USB TMC capabilities as described
by the device itself. The full description of the bitfields
can be found in the USB TMC documents from the USB-IF entitled
"Universal Serial Bus Test and Measurement Class Specification
(USBTMC) Revision 1.0" section 4.2.1.8.
The files are read only.
What: /sys/bus/usb/drivers/usbtmc/devices/*/usb488_interface_capabilities
What: /sys/bus/usb/drivers/usbtmc/devices/*/usb488_device_capabilities
Date: August 2008
Contact: Greg Kroah-Hartman <gregkh@suse.de>
Description:
These files show the various USB TMC capabilities as described
by the device itself. The full description of the bitfields
can be found in the USB TMC documents from the USB-IF entitled
"Universal Serial Bus Test and Measurement Class, Subclass
USB488 Specification (USBTMC-USB488) Revision 1.0" section
4.2.2.
The files are read only.
What: /sys/bus/usb/drivers/usbtmc/devices/*/TermChar
Date: August 2008
Contact: Greg Kroah-Hartman <gregkh@suse.de>
Description:
This file is the TermChar value to be sent to the USB TMC
device as described by the document, "Universal Serial Bus Test
and Measurement Class Specification
(USBTMC) Revision 1.0" as published by the USB-IF.
Note that the TermCharEnabled file determines if this value is
sent to the device or not.
What: /sys/bus/usb/drivers/usbtmc/devices/*/TermCharEnabled
Date: August 2008
Contact: Greg Kroah-Hartman <gregkh@suse.de>
Description:
This file determines if the TermChar is to be sent to the
device on every transaction or not. For more details about
this, please see the document, "Universal Serial Bus Test and
Measurement Class Specification (USBTMC) Revision 1.0" as
published by the USB-IF.
What: /sys/bus/usb/drivers/usbtmc/devices/*/auto_abort
Date: August 2008
Contact: Greg Kroah-Hartman <gregkh@suse.de>
Description:
This file determines if the the transaction of the USB TMC
device is to be automatically aborted if there is any error.
For more details about this, please see the document,
"Universal Serial Bus Test and Measurement Class Specification
(USBTMC) Revision 1.0" as published by the USB-IF.

16
Documentation/ABI/testing/sysfs-bus-usb
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@ -85,3 +85,19 @@ Description:
Users:
PowerTOP <power@bughost.org>
http://www.lesswatts.org/projects/powertop/
What: /sys/bus/usb/device/<busnum>-<devnum>...:<config num>-<interface num>/supports_autosuspend
Date: January 2008
KernelVersion: 2.6.27
Contact: Sarah Sharp <sarah.a.sharp@intel.com>
Description:
When read, this file returns 1 if the interface driver
for this interface supports autosuspend. It also
returns 1 if no driver has claimed this interface, as an
unclaimed interface will not stop the device from being
autosuspended if all other interface drivers are idle.
The file returns 0 if autosuspend support has not been
added to the driver.
Users:
USB PM tool
git://git.moblin.org/users/sarah/usb-pm-tool/

43
Documentation/ABI/testing/sysfs-bus-usb-devices-usbsevseg Normal file
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@ -0,0 +1,43 @@
Where: /sys/bus/usb/.../powered
Date: August 2008
Kernel Version: 2.6.26
Contact: Harrison Metzger <harrisonmetz@gmail.com>
Description: Controls whether the device's display will powered.
A value of 0 is off and a non-zero value is on.
Where: /sys/bus/usb/.../mode_msb
Where: /sys/bus/usb/.../mode_lsb
Date: August 2008
Kernel Version: 2.6.26
Contact: Harrison Metzger <harrisonmetz@gmail.com>
Description: Controls the devices display mode.
For a 6 character display the values are
MSB 0x06; LSB 0x3F, and
for an 8 character display the values are
MSB 0x08; LSB 0xFF.
Where: /sys/bus/usb/.../textmode
Date: August 2008
Kernel Version: 2.6.26
Contact: Harrison Metzger <harrisonmetz@gmail.com>
Description: Controls the way the device interprets its text buffer.
raw: each character controls its segment manually
hex: each character is between 0-15
ascii: each character is between '0'-'9' and 'A'-'F'.
Where: /sys/bus/usb/.../text
Date: August 2008
Kernel Version: 2.6.26
Contact: Harrison Metzger <harrisonmetz@gmail.com>
Description: The text (or data) for the device to display
Where: /sys/bus/usb/.../decimals
Date: August 2008
Kernel Version: 2.6.26
Contact: Harrison Metzger <harrisonmetz@gmail.com>
Description: Controls the decimal places on the device.
To set the nth decimal place, give this field
the value of 10 ** n. Assume this field has
the value k and has 1 or more decimal places set,
to set the mth place (where m is not already set),
change this fields value to k + 10 ** m.

55
Documentation/ABI/testing/sysfs-class-regulator
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@ -1,7 +1,7 @@
What: /sys/class/regulator/.../state
Date: April 2008
KernelVersion: 2.6.26
Contact: Liam Girdwood <lg@opensource.wolfsonmicro.com>
Contact: Liam Girdwood <lrg@slimlogic.co.uk>
Description:
Each regulator directory will contain a field called
state. This holds the regulator output state.
@ -27,7 +27,7 @@ Description:
What: /sys/class/regulator/.../type
Date: April 2008
KernelVersion: 2.6.26
Contact: Liam Girdwood <lg@opensource.wolfsonmicro.com>
Contact: Liam Girdwood <lrg@slimlogic.co.uk>
Description:
Each regulator directory will contain a field called
type. This holds the regulator type.
@ -51,7 +51,7 @@ Description:
What: /sys/class/regulator/.../microvolts
Date: April 2008
KernelVersion: 2.6.26
Contact: Liam Girdwood <lg@opensource.wolfsonmicro.com>
Contact: Liam Girdwood <lrg@slimlogic.co.uk>
Description:
Each regulator directory will contain a field called
microvolts. This holds the regulator output voltage setting
@ -65,7 +65,7 @@ Description:
What: /sys/class/regulator/.../microamps
Date: April 2008
KernelVersion: 2.6.26
Contact: Liam Girdwood <lg@opensource.wolfsonmicro.com>
Contact: Liam Girdwood <lrg@slimlogic.co.uk>
Description:
Each regulator directory will contain a field called
microamps. This holds the regulator output current limit
@ -79,7 +79,7 @@ Description:
What: /sys/class/regulator/.../opmode
Date: April 2008
KernelVersion: 2.6.26
Contact: Liam Girdwood <lg@opensource.wolfsonmicro.com>
Contact: Liam Girdwood <lrg@slimlogic.co.uk>
Description:
Each regulator directory will contain a field called
opmode. This holds the regulator operating mode setting.
@ -102,7 +102,7 @@ Description:
What: /sys/class/regulator/.../min_microvolts
Date: April 2008
KernelVersion: 2.6.26
Contact: Liam Girdwood <lg@opensource.wolfsonmicro.com>
Contact: Liam Girdwood <lrg@slimlogic.co.uk>
Description:
Each regulator directory will contain a field called
min_microvolts. This holds the minimum safe working regulator
@ -116,7 +116,7 @@ Description:
What: /sys/class/regulator/.../max_microvolts
Date: April 2008
KernelVersion: 2.6.26
Contact: Liam Girdwood <lg@opensource.wolfsonmicro.com>
Contact: Liam Girdwood <lrg@slimlogic.co.uk>
Description:
Each regulator directory will contain a field called
max_microvolts. This holds the maximum safe working regulator
@ -130,7 +130,7 @@ Description:
What: /sys/class/regulator/.../min_microamps
Date: April 2008
KernelVersion: 2.6.26
Contact: Liam Girdwood <lg@opensource.wolfsonmicro.com>
Contact: Liam Girdwood <lrg@slimlogic.co.uk>
Description:
Each regulator directory will contain a field called
min_microamps. This holds the minimum safe working regulator
@ -145,7 +145,7 @@ Description:
What: /sys/class/regulator/.../max_microamps
Date: April 2008
KernelVersion: 2.6.26
Contact: Liam Girdwood <lg@opensource.wolfsonmicro.com>
Contact: Liam Girdwood <lrg@slimlogic.co.uk>
Description:
Each regulator directory will contain a field called
max_microamps. This holds the maximum safe working regulator
@ -157,10 +157,23 @@ Description:
platform code.
What: /sys/class/regulator/.../name
Date: October 2008
KernelVersion: 2.6.28
Contact: Liam Girdwood <lrg@slimlogic.co.uk>
Description:
Each regulator directory will contain a field called
name. This holds a string identifying the regulator for
display purposes.
NOTE: this will be empty if no suitable name is provided
by platform or regulator drivers.
What: /sys/class/regulator/.../num_users
Date: April 2008
KernelVersion: 2.6.26
Contact: Liam Girdwood <lg@opensource.wolfsonmicro.com>
Contact: Liam Girdwood <lrg@slimlogic.co.uk>
Description:
Each regulator directory will contain a field called
num_users. This holds the number of consumer devices that
@ -170,7 +183,7 @@ Description:
What: /sys/class/regulator/.../requested_microamps
Date: April 2008
KernelVersion: 2.6.26
Contact: Liam Girdwood <lg@opensource.wolfsonmicro.com>
Contact: Liam Girdwood <lrg@slimlogic.co.uk>
Description:
Each regulator directory will contain a field called
requested_microamps. This holds the total requested load
@ -181,7 +194,7 @@ Description:
What: /sys/class/regulator/.../parent
Date: April 2008
KernelVersion: 2.6.26
Contact: Liam Girdwood <lg@opensource.wolfsonmicro.com>
Contact: Liam Girdwood <lrg@slimlogic.co.uk>
Description:
Some regulator directories will contain a link called parent.
This points to the parent or supply regulator if one exists.
@ -189,7 +202,7 @@ Description:
What: /sys/class/regulator/.../suspend_mem_microvolts
Date: May 2008
KernelVersion: 2.6.26
Contact: Liam Girdwood <lg@opensource.wolfsonmicro.com>
Contact: Liam Girdwood <lrg@slimlogic.co.uk>
Description:
Each regulator directory will contain a field called
suspend_mem_microvolts. This holds the regulator output
@ -203,7 +216,7 @@ Description:
What: /sys/class/regulator/.../suspend_disk_microvolts
Date: May 2008
KernelVersion: 2.6.26
Contact: Liam Girdwood <lg@opensource.wolfsonmicro.com>
Contact: Liam Girdwood <lrg@slimlogic.co.uk>
Description:
Each regulator directory will contain a field called
suspend_disk_microvolts. This holds the regulator output
@ -217,7 +230,7 @@ Description:
What: /sys/class/regulator/.../suspend_standby_microvolts
Date: May 2008
KernelVersion: 2.6.26
Contact: Liam Girdwood <lg@opensource.wolfsonmicro.com>
Contact: Liam Girdwood <lrg@slimlogic.co.uk>
Description:
Each regulator directory will contain a field called
suspend_standby_microvolts. This holds the regulator output
@ -231,7 +244,7 @@ Description:
What: /sys/class/regulator/.../suspend_mem_mode
Date: May 2008
KernelVersion: 2.6.26
Contact: Liam Girdwood <lg@opensource.wolfsonmicro.com>
Contact: Liam Girdwood <lrg@slimlogic.co.uk>
Description:
Each regulator directory will contain a field called
suspend_mem_mode. This holds the regulator operating mode
@ -245,7 +258,7 @@ Description:
What: /sys/class/regulator/.../suspend_disk_mode
Date: May 2008
KernelVersion: 2.6.26
Contact: Liam Girdwood <lg@opensource.wolfsonmicro.com>
Contact: Liam Girdwood <lrg@slimlogic.co.uk>
Description:
Each regulator directory will contain a field called
suspend_disk_mode. This holds the regulator operating mode
@ -258,7 +271,7 @@ Description:
What: /sys/class/regulator/.../suspend_standby_mode
Date: May 2008
KernelVersion: 2.6.26
Contact: Liam Girdwood <lg@opensource.wolfsonmicro.com>
Contact: Liam Girdwood <lrg@slimlogic.co.uk>
Description:
Each regulator directory will contain a field called
suspend_standby_mode. This holds the regulator operating mode
@ -272,7 +285,7 @@ Description:
What: /sys/class/regulator/.../suspend_mem_state
Date: May 2008
KernelVersion: 2.6.26
Contact: Liam Girdwood <lg@opensource.wolfsonmicro.com>
Contact: Liam Girdwood <lrg@slimlogic.co.uk>
Description:
Each regulator directory will contain a field called
suspend_mem_state. This holds the regulator operating state
@ -287,7 +300,7 @@ Description:
What: /sys/class/regulator/.../suspend_disk_state
Date: May 2008
KernelVersion: 2.6.26
Contact: Liam Girdwood <lg@opensource.wolfsonmicro.com>
Contact: Liam Girdwood <lrg@slimlogic.co.uk>
Description:
Each regulator directory will contain a field called
suspend_disk_state. This holds the regulator operating state
@ -302,7 +315,7 @@ Description:
What: /sys/class/regulator/.../suspend_standby_state
Date: May 2008
KernelVersion: 2.6.26
Contact: Liam Girdwood <lg@opensource.wolfsonmicro.com>
Contact: Liam Girdwood <lrg@slimlogic.co.uk>
Description:
Each regulator directory will contain a field called
suspend_standby_state. This holds the regulator operating

13
Documentation/ABI/testing/sysfs-profiling Normal file
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@ -0,0 +1,13 @@
What: /sys/kernel/profile
Date: September 2008
Contact: Dave Hansen <dave@linux.vnet.ibm.com>
Description:
/sys/kernel/profile is the runtime equivalent
of the boot-time profile= option.
You can get the same effect running:
echo 2 > /sys/kernel/profile
as you would by issuing profile=2 on the boot
command line.

2
Documentation/DMA-API.txt
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@ -337,7 +337,7 @@ With scatterlists, you use the resulting mapping like this:
int i, count = dma_map_sg(dev, sglist, nents, direction);
struct scatterlist *sg;
for (i = 0, sg = sglist; i < count; i++, sg++) {
for_each_sg(sglist, sg, count, i) {
hw_address[i] = sg_dma_address(sg);
hw_len[i] = sg_dma_len(sg);
}

2
Documentation/DocBook/Makefile
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@ -6,7 +6,7 @@
# To add a new book the only step required is to add the book to the
# list of DOCBOOKS.
DOCBOOKS := wanbook.xml z8530book.xml mcabook.xml videobook.xml \
DOCBOOKS := wanbook.xml z8530book.xml mcabook.xml \
kernel-hacking.xml kernel-locking.xml deviceiobook.xml \
procfs-guide.xml writing_usb_driver.xml networking.xml \
kernel-api.xml filesystems.xml lsm.xml usb.xml kgdb.xml \

3
Documentation/DocBook/gadget.tmpl
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@ -557,6 +557,9 @@ Near-term plans include converting all of them, except for "gadgetfs".
</para>
!Edrivers/usb/gadget/f_acm.c
!Edrivers/usb/gadget/f_ecm.c
!Edrivers/usb/gadget/f_subset.c
!Edrivers/usb/gadget/f_obex.c
!Edrivers/usb/gadget/f_serial.c
</sect1>

5
Documentation/DocBook/kernel-api.tmpl
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@ -283,6 +283,7 @@ X!Earch/x86/kernel/mca_32.c
<chapter id="security">
<title>Security Framework</title>
!Isecurity/security.c
!Esecurity/inode.c
</chapter>
<chapter id="audit">
@ -364,6 +365,10 @@ X!Edrivers/pnp/system.c
!Eblock/blk-barrier.c
!Eblock/blk-tag.c
!Iblock/blk-tag.c
!Eblock/blk-integrity.c
!Iblock/blktrace.c
!Iblock/genhd.c
!Eblock/genhd.c
</chapter>
<chapter id="chrdev">

2
Documentation/DocBook/kernel-hacking.tmpl
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@ -1105,7 +1105,7 @@ static struct block_device_operations opt_fops = {
</listitem>
<listitem>
<para>
Function names as strings (__FUNCTION__).
Function names as strings (__func__).
</para>
</listitem>
<listitem>

12
Documentation/DocBook/mac80211.tmpl
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@ -145,7 +145,6 @@ usage should require reading the full document.
this though and the recommendation to allow only a single
interface in STA mode at first!
</para>
!Finclude/net/mac80211.h ieee80211_if_types
!Finclude/net/mac80211.h ieee80211_if_init_conf
!Finclude/net/mac80211.h ieee80211_if_conf
</chapter>
@ -177,8 +176,7 @@ usage should require reading the full document.
<title>functions/definitions</title>
!Finclude/net/mac80211.h ieee80211_rx_status
!Finclude/net/mac80211.h mac80211_rx_flags
!Finclude/net/mac80211.h ieee80211_tx_control
!Finclude/net/mac80211.h ieee80211_tx_status_flags
!Finclude/net/mac80211.h ieee80211_tx_info
!Finclude/net/mac80211.h ieee80211_rx
!Finclude/net/mac80211.h ieee80211_rx_irqsafe
!Finclude/net/mac80211.h ieee80211_tx_status
@ -189,12 +187,11 @@ usage should require reading the full document.
!Finclude/net/mac80211.h ieee80211_ctstoself_duration
!Finclude/net/mac80211.h ieee80211_generic_frame_duration
!Finclude/net/mac80211.h ieee80211_get_hdrlen_from_skb
!Finclude/net/mac80211.h ieee80211_get_hdrlen
!Finclude/net/mac80211.h ieee80211_hdrlen
!Finclude/net/mac80211.h ieee80211_wake_queue
!Finclude/net/mac80211.h ieee80211_stop_queue
!Finclude/net/mac80211.h ieee80211_start_queues
!Finclude/net/mac80211.h ieee80211_stop_queues
!Finclude/net/mac80211.h ieee80211_wake_queues
!Finclude/net/mac80211.h ieee80211_stop_queues
</sect1>
</chapter>
@ -230,8 +227,7 @@ usage should require reading the full document.
<title>Multiple queues and QoS support</title>
<para>TBD</para>
!Finclude/net/mac80211.h ieee80211_tx_queue_params
!Finclude/net/mac80211.h ieee80211_tx_queue_stats_data
!Finclude/net/mac80211.h ieee80211_tx_queue
!Finclude/net/mac80211.h ieee80211_tx_queue_stats
</chapter>
<chapter id="AP">

29
Documentation/DocBook/procfs-guide.tmpl
View File

@ -14,17 +14,20 @@
<othername>(J.A.K.)</othername>
<surname>Mouw</surname>
<affiliation>
<orgname>Delft University of Technology</orgname>
<orgdiv>Faculty of Information Technology and Systems</orgdiv>
<address>
<email>J.A.K.Mouw@its.tudelft.nl</email>
<pob>PO BOX 5031</pob>
<postcode>2600 GA</postcode>
<city>Delft</city>
<country>The Netherlands</country>
<email>mouw@nl.linux.org</email>
</address>
</affiliation>
</author>
<othercredit>
<contrib>
This software and documentation were written while working on the
LART computing board
(<ulink url="http://www.lartmaker.nl/">http://www.lartmaker.nl/</ulink>),
which was sponsored by the Delt University of Technology projects
Mobile Multi-media Communications and Ubiquitous Communications.
</contrib>
</othercredit>
</authorgroup>
<revhistory>
@ -108,18 +111,6 @@
proofreading.
</para>
<para>
This documentation was written while working on the LART
computing board (<ulink
url="http://www.lart.tudelft.nl/">http://www.lart.tudelft.nl/</ulink>),
which is sponsored by the Mobile Multi-media Communications
(<ulink
url="http://www.mmc.tudelft.nl/">http://www.mmc.tudelft.nl/</ulink>)
and Ubiquitous Communications (<ulink
url="http://www.ubicom.tudelft.nl/">http://www.ubicom.tudelft.nl/</ulink>)
projects.
</para>
<para>
Erik
</para>

20
Documentation/DocBook/procfs_example.c
View File

@ -1,28 +1,16 @@
/*
* procfs_example.c: an example proc interface
*
* Copyright (C) 2001, Erik Mouw (J.A.K.Mouw@its.tudelft.nl)
* Copyright (C) 2001, Erik Mouw (mouw@nl.linux.org)
*
* This file accompanies the procfs-guide in the Linux kernel
* source. Its main use is to demonstrate the concepts and
* functions described in the guide.
*
* This software has been developed while working on the LART
* computing board (http://www.lart.tudelft.nl/), which is
* sponsored by the Mobile Multi-media Communications
* (http://www.mmc.tudelft.nl/) and Ubiquitous Communications
* (http://www.ubicom.tudelft.nl/) projects.
*
* The author can be reached at:
*
* Erik Mouw
* Information and Communication Theory Group
* Faculty of Information Technology and Systems
* Delft University of Technology
* P.O. Box 5031
* 2600 GA Delft
* The Netherlands
*
* computing board (http://www.lartmaker.nl), which was sponsored
* by the Delt University of Technology projects Mobile Multi-media
* Communications and Ubiquitous Communications.
*
* This program is free software; you can redistribute
* it and/or modify it under the terms of the GNU General

1654
Documentation/DocBook/videobook.tmpl
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File diff suppressed because it is too large Load Diff

4
Documentation/HOWTO
View File

@ -112,7 +112,7 @@ required reading:
Other excellent descriptions of how to create patches properly are:
"The Perfect Patch"
http://www.zip.com.au/~akpm/linux/patches/stuff/tpp.txt
http://userweb.kernel.org/~akpm/stuff/tpp.txt
"Linux kernel patch submission format"
http://linux.yyz.us/patch-format.html
@ -620,7 +620,7 @@ all time. It should describe the patch completely, containing:
For more details on what this should all look like, please see the
ChangeLog section of the document:
"The Perfect Patch"
http://www.zip.com.au/~akpm/linux/patches/stuff/tpp.txt
http://userweb.kernel.org/~akpm/stuff/tpp.txt

6
Documentation/MSI-HOWTO.txt
View File

@ -236,10 +236,8 @@ software system can set different pages for controlling accesses to the
MSI-X structure. The implementation of MSI support requires the PCI
subsystem, not a device driver, to maintain full control of the MSI-X
table/MSI-X PBA (Pending Bit Array) and MMIO address space of the MSI-X
table/MSI-X PBA. A device driver is prohibited from requesting the MMIO
address space of the MSI-X table/MSI-X PBA. Otherwise, the PCI subsystem
will fail enabling MSI-X on its hardware device when it calls the function
pci_enable_msix().
table/MSI-X PBA. A device driver should not access the MMIO address
space of the MSI-X table/MSI-X PBA.
5.3.2 API pci_enable_msix

4
Documentation/PCI/pci.txt
View File

@ -163,6 +163,10 @@ need pass only as many optional fields as necessary:
o class and classmask fields default to 0
o driver_data defaults to 0UL.
Note that driver_data must match the value used by any of the pci_device_id
entries defined in the driver. This makes the driver_data field mandatory
if all the pci_device_id entries have a non-zero driver_data value.
Once added, the driver probe routine will be invoked for any unclaimed
PCI devices listed in its (newly updated) pci_ids list.

11
Documentation/PCI/pcieaer-howto.txt
View File

@ -203,22 +203,17 @@ to mmio_enabled.
3.3 helper functions
3.3.1 int pci_find_aer_capability(struct pci_dev *dev);
pci_find_aer_capability locates the PCI Express AER capability
in the device configuration space. If the device doesn't support
PCI-Express AER, the function returns 0.
3.3.2 int pci_enable_pcie_error_reporting(struct pci_dev *dev);
3.3.1 int pci_enable_pcie_error_reporting(struct pci_dev *dev);
pci_enable_pcie_error_reporting enables the device to send error
messages to root port when an error is detected. Note that devices
don't enable the error reporting by default, so device drivers need
call this function to enable it.
3.3.3 int pci_disable_pcie_error_reporting(struct pci_dev *dev);
3.3.2 int pci_disable_pcie_error_reporting(struct pci_dev *dev);
pci_disable_pcie_error_reporting disables the device to send error
messages to root port when an error is detected.
3.3.4 int pci_cleanup_aer_uncorrect_error_status(struct pci_dev *dev);
3.3.3 int pci_cleanup_aer_uncorrect_error_status(struct pci_dev *dev);
pci_cleanup_aer_uncorrect_error_status cleanups the uncorrectable
error status register.

2
Documentation/RCU/checklist.txt
View File

@ -210,7 +210,7 @@ over a rather long period of time, but improvements are always welcome!
number of updates per grace period.
9. All RCU list-traversal primitives, which include
rcu_dereference(), list_for_each_rcu(), list_for_each_entry_rcu(),
rcu_dereference(), list_for_each_entry_rcu(),
list_for_each_continue_rcu(), and list_for_each_safe_rcu(),
must be either within an RCU read-side critical section or
must be protected by appropriate update-side locks. RCU

16
Documentation/RCU/rcuref.txt
View File

@ -29,9 +29,9 @@ release_referenced() delete()
}
If this list/array is made lock free using RCU as in changing the
write_lock() in add() and delete() to spin_lock and changing read_lock
in search_and_reference to rcu_read_lock(), the atomic_get in
search_and_reference could potentially hold reference to an element which
write_lock() in add() and delete() to spin_lock() and changing read_lock()
in search_and_reference() to rcu_read_lock(), the atomic_inc() in
search_and_reference() could potentially hold reference to an element which
has already been deleted from the list/array. Use atomic_inc_not_zero()
in this scenario as follows:
@ -40,20 +40,20 @@ add() search_and_reference()
{ {
alloc_object rcu_read_lock();
... search_for_element
atomic_set(&el->rc, 1); if (atomic_inc_not_zero(&el->rc)) {
write_lock(&list_lock); rcu_read_unlock();
atomic_set(&el->rc, 1); if (!atomic_inc_not_zero(&el->rc)) {
spin_lock(&list_lock); rcu_read_unlock();
return FAIL;
add_element }
... ...
write_unlock(&list_lock); rcu_read_unlock();
spin_unlock(&list_lock); rcu_read_unlock();
} }
3. 4.
release_referenced() delete()
{ {
... write_lock(&list_lock);
... spin_lock(&list_lock);
if (atomic_dec_and_test(&el->rc)) ...
call_rcu(&el->head, el_free); delete_element
... write_unlock(&list_lock);
... spin_unlock(&list_lock);
} ...
if (atomic_dec_and_test(&el->rc))
call_rcu(&el->head, el_free);

2
Documentation/RCU/whatisRCU.txt
View File

@ -786,8 +786,6 @@ RCU pointer/list traversal:
list_for_each_entry_rcu
hlist_for_each_entry_rcu
list_for_each_rcu (to be deprecated in favor of
list_for_each_entry_rcu)
list_for_each_continue_rcu (to be deprecated in favor of new
list_for_each_entry_continue_rcu)

2
Documentation/SAK.txt
View File

@ -1,5 +1,5 @@
Linux 2.4.2 Secure Attention Key (SAK) handling
18 March 2001, Andrew Morton <akpm@osdl.org>
18 March 2001, Andrew Morton
An operating system's Secure Attention Key is a security tool which is
provided as protection against trojan password capturing programs. It

27
Documentation/SELinux.txt Normal file
View File

@ -0,0 +1,27 @@
If you want to use SELinux, chances are you will want
to use the distro-provided policies, or install the
latest reference policy release from
http://oss.tresys.com/projects/refpolicy
However, if you want to install a dummy policy for
testing, you can do using 'mdp' provided under
scripts/selinux. Note that this requires the selinux
userspace to be installed - in particular you will
need checkpolicy to compile a kernel, and setfiles and
fixfiles to label the filesystem.
1. Compile the kernel with selinux enabled.
2. Type 'make' to compile mdp.
3. Make sure that you are not running with
SELinux enabled and a real policy. If
you are, reboot with selinux disabled
before continuing.
4. Run install_policy.sh:
cd scripts/selinux
sh install_policy.sh
Step 4 will create a new dummy policy valid for your
kernel, with a single selinux user, role, and type.
It will compile the policy, will set your SELINUXTYPE to
dummy in /etc/selinux/config, install the compiled policy
as 'dummy', and relabel your filesystem.

3
Documentation/SubmitChecklist
View File

@ -85,3 +85,6 @@ kernel patches.
23: Tested after it has been merged into the -mm patchset to make sure
that it still works with all of the other queued patches and various
changes in the VM, VFS, and other subsystems.
24: All memory barriers {e.g., barrier(), rmb(), wmb()} need a comment in the
source code that explains the logic of what they are doing and why.

2
Documentation/SubmittingDrivers
View File

@ -41,7 +41,7 @@ Linux 2.4:
Linux 2.6:
The same rules apply as 2.4 except that you should follow linux-kernel
to track changes in API's. The final contact point for Linux 2.6
submissions is Andrew Morton <akpm@osdl.org>.
submissions is Andrew Morton.
What Criteria Determine Acceptance
----------------------------------

11
Documentation/SubmittingPatches
View File

@ -77,7 +77,7 @@ Quilt:
http://savannah.nongnu.org/projects/quilt
Andrew Morton's patch scripts:
http://www.zip.com.au/~akpm/linux/patches/
http://userweb.kernel.org/~akpm/stuff/patch-scripts.tar.gz
Instead of these scripts, quilt is the recommended patch management
tool (see above).
@ -405,7 +405,7 @@ person it names. This tag documents that potentially interested parties
have been included in the discussion
14) Using Test-by: and Reviewed-by:
14) Using Tested-by: and Reviewed-by:
A Tested-by: tag indicates that the patch has been successfully tested (in
some environment) by the person named. This tag informs maintainers that
@ -653,7 +653,7 @@ SECTION 3 - REFERENCES
----------------------
Andrew Morton, "The perfect patch" (tpp).
<http://www.zip.com.au/~akpm/linux/patches/stuff/tpp.txt>
<http://userweb.kernel.org/~akpm/stuff/tpp.txt>
Jeff Garzik, "Linux kernel patch submission format".
<http://linux.yyz.us/patch-format.html>
@ -672,4 +672,9 @@ Kernel Documentation/CodingStyle:
Linus Torvalds's mail on the canonical patch format:
<http://lkml.org/lkml/2005/4/7/183>
Andi Kleen, "On submitting kernel patches"
Some strategies to get difficult or controversal changes in.
http://halobates.de/on-submitting-patches.pdf
--

155
Documentation/blackfin/kgdb.txt
View File

@ -1,155 +0,0 @@
A Simple Guide to Configure KGDB
Sonic Zhang <sonic.zhang@analog.com>
Aug. 24th 2006
This KGDB patch enables the kernel developer to do source level debugging on
the kernel for the Blackfin architecture. The debugging works over either the
ethernet interface or one of the uarts. Both software breakpoints and
hardware breakpoints are supported in this version.
http://docs.blackfin.uclinux.org/doku.php?id=kgdb
2 known issues:
1. This bug:
http://blackfin.uclinux.org/tracker/index.php?func=detail&aid=544&group_id=18&atid=145
The GDB client for Blackfin uClinux causes incorrect values of local
variables to be displayed when the user breaks the running of kernel in GDB.
2. Because of a hardware bug in Blackfin 533 v1.0.3:
05000067 - Watchpoints (Hardware Breakpoints) are not supported
Hardware breakpoints cannot be set properly.
Debug over Ethernet:
1. Compile and install the cross platform version of gdb for blackfin, which
can be found at $(BINROOT)/bfin-elf-gdb.
2. Apply this patch to the 2.6.x kernel. Select the menuconfig option under
"Kernel hacking" -> "Kernel debugging" -> "KGDB: kernel debug with remote gdb".
With this selected, option "Full Symbolic/Source Debugging support" and
"Compile the kernel with frame pointers" are also selected.
3. Select option "KGDB: connect over (Ethernet)". Add "kgdboe=@target-IP/,@host-IP/" to
the option "Compiled-in Kernel Boot Parameter" under "Kernel hacking".
4. Connect minicom to the serial port and boot the kernel image.
5. Configure the IP "/> ifconfig eth0 target-IP"
6. Start GDB client "bfin-elf-gdb vmlinux".
7. Connect to the target "(gdb) target remote udp:target-IP:6443".
8. Set software breakpoint "(gdb) break sys_open".
9. Continue "(gdb) c".
10. Run ls in the target console "/> ls".
11. Breakpoint hits. "Breakpoint 1: sys_open(..."
12. Display local variables and function paramters.
(*) This operation gives wrong results, see known issue 1.
13. Single stepping "(gdb) si".
14. Remove breakpoint 1. "(gdb) del 1"
15. Set hardware breakpoint "(gdb) hbreak sys_open".
16. Continue "(gdb) c".
17. Run ls in the target console "/> ls".
18. Hardware breakpoint hits. "Breakpoint 1: sys_open(...".
(*) This hardware breakpoint will not be hit, see known issue 2.
19. Continue "(gdb) c".
20. Interrupt the target in GDB "Ctrl+C".
21. Detach from the target "(gdb) detach".
22. Exit GDB "(gdb) quit".
Debug over the UART:
1. Compile and install the cross platform version of gdb for blackfin, which
can be found at $(BINROOT)/bfin-elf-gdb.
2. Apply this patch to the 2.6.x kernel. Select the menuconfig option under
"Kernel hacking" -> "Kernel debugging" -> "KGDB: kernel debug with remote gdb".
With this selected, option "Full Symbolic/Source Debugging support" and
"Compile the kernel with frame pointers" are also selected.
3. Select option "KGDB: connect over (UART)". Set "KGDB: UART port number" to be
a different one from the console. Don't forget to change the mode of
blackfin serial driver to PIO. Otherwise kgdb works incorrectly on UART.
4. If you want connect to kgdb when the kernel boots, enable
"KGDB: Wait for gdb connection early"
5. Compile kernel.
6. Connect minicom to the serial port of the console and boot the kernel image.
7. Start GDB client "bfin-elf-gdb vmlinux".
8. Set the baud rate in GDB "(gdb) set remotebaud 57600".
9. Connect to the target on the second serial port "(gdb) target remote /dev/ttyS1".
10. Set software breakpoint "(gdb) break sys_open".
11. Continue "(gdb) c".
12. Run ls in the target console "/> ls".
13. A breakpoint is hit. "Breakpoint 1: sys_open(..."
14. All other operations are the same as that in KGDB over Ethernet.
Debug over the same UART as console:
1. Compile and install the cross platform version of gdb for blackfin, which
can be found at $(BINROOT)/bfin-elf-gdb.
2. Apply this patch to the 2.6.x kernel. Select the menuconfig option under
"Kernel hacking" -> "Kernel debugging" -> "KGDB: kernel debug with remote gdb".
With this selected, option "Full Symbolic/Source Debugging support" and
"Compile the kernel with frame pointers" are also selected.
3. Select option "KGDB: connect over UART". Set "KGDB: UART port number" to console.
Don't forget to change the mode of blackfin serial driver to PIO.
Otherwise kgdb works incorrectly on UART.
4. If you want connect to kgdb when the kernel boots, enable
"KGDB: Wait for gdb connection early"
5. Connect minicom to the serial port and boot the kernel image.
6. (Optional) Ask target to wait for gdb connection by entering Ctrl+A. In minicom, you should enter Ctrl+A+A.
7. Start GDB client "bfin-elf-gdb vmlinux".
8. Set the baud rate in GDB "(gdb) set remotebaud 57600".
9. Connect to the target "(gdb) target remote /dev/ttyS0".
10. Set software breakpoint "(gdb) break sys_open".
11. Continue "(gdb) c". Then enter Ctrl+C twice to stop GDB connection.
12. Run ls in the target console "/> ls". Dummy string can be seen on the console.
13. Then connect the gdb to target again. "(gdb) target remote /dev/ttyS0".
Now you will find a breakpoint is hit. "Breakpoint 1: sys_open(..."
14. All other operations are the same as that in KGDB over Ethernet. The only
difference is that after continue command in GDB, please stop GDB
connection by 2 "Ctrl+C"s and connect again after breakpoints are hit or
Ctrl+A is entered.

4
Documentation/block/data-integrity.txt
View File

@ -246,7 +246,7 @@ will require extra work due to the application tag.
retrieve the tag buffer using bio_integrity_get_tag().
6.3 PASSING EXISTING INTEGRITY METADATA
5.3 PASSING EXISTING INTEGRITY METADATA
Filesystems that either generate their own integrity metadata or
are capable of transferring IMD from user space can use the
@ -283,7 +283,7 @@ will require extra work due to the application tag.
integrity upon completion.
6.4 REGISTERING A BLOCK DEVICE AS CAPABLE OF EXCHANGING INTEGRITY
5.4 REGISTERING A BLOCK DEVICE AS CAPABLE OF EXCHANGING INTEGRITY
METADATA
To enable integrity exchange on a block device the gendisk must be

14
Documentation/block/deadline-iosched.txt
View File

@ -30,12 +30,18 @@ write_expire (in ms)
Similar to read_expire mentioned above, but for writes.
fifo_batch
fifo_batch (number of requests)
----------
When a read request expires its deadline, we must move some requests from
the sorted io scheduler list to the block device dispatch queue. fifo_batch
controls how many requests we move.
Requests are grouped into ``batches'' of a particular data direction (read or
write) which are serviced in increasing sector order. To limit extra seeking,
deadline expiries are only checked between batches. fifo_batch controls the
maximum number of requests per batch.
This parameter tunes the balance between per-request latency and aggregate
throughput. When low latency is the primary concern, smaller is better (where
a value of 1 yields first-come first-served behaviour). Increasing fifo_batch
generally improves throughput, at the cost of latency variation.
writes_starved (number of dispatches)

3
Documentation/cdrom/ide-cd
View File

@ -145,8 +145,7 @@ useful for reading photocds.
To play an audio CD, you should first unmount and remove any data
CDROM. Any of the CDROM player programs should then work (workman,
workbone, cdplayer, etc.). Lacking anything else, you could use the
cdtester program in Documentation/cdrom/sbpcd.
workbone, cdplayer, etc.).
On a few drives, you can read digital audio directly using a program
such as cdda2wav. The only types of drive which I've heard support

0
Documentation/cgroups.txt → Documentation/cgroups/cgroups.txt
View File

99
Documentation/cgroups/freezer-subsystem.txt Normal file
View File

@ -0,0 +1,99 @@
The cgroup freezer is useful to batch job management system which start
and stop sets of tasks in order to schedule the resources of a machine
according to the desires of a system administrator. This sort of program
is often used on HPC clusters to schedule access to the cluster as a
whole. The cgroup freezer uses cgroups to describe the set of tasks to
be started/stopped by the batch job management system. It also provides
a means to start and stop the tasks composing the job.
The cgroup freezer will also be useful for checkpointing running groups
of tasks. The freezer allows the checkpoint code to obtain a consistent
image of the tasks by attempting to force the tasks in a cgroup into a
quiescent state. Once the tasks are quiescent another task can
walk /proc or invoke a kernel interface to gather information about the
quiesced tasks. Checkpointed tasks can be restarted later should a
recoverable error occur. This also allows the checkpointed tasks to be
migrated between nodes in a cluster by copying the gathered information
to another node and restarting the tasks there.
Sequences of SIGSTOP and SIGCONT are not always sufficient for stopping
and resuming tasks in userspace. Both of these signals are observable
from within the tasks we wish to freeze. While SIGSTOP cannot be caught,
blocked, or ignored it can be seen by waiting or ptracing parent tasks.
SIGCONT is especially unsuitable since it can be caught by the task. Any
programs designed to watch for SIGSTOP and SIGCONT could be broken by
attempting to use SIGSTOP and SIGCONT to stop and resume tasks. We can
demonstrate this problem using nested bash shells:
$ echo $$
16644
$ bash
$ echo $$
16690
From a second, unrelated bash shell:
$ kill -SIGSTOP 16690
$ kill -SIGCONT 16990
<at this point 16990 exits and causes 16644 to exit too>
This happens because bash can observe both signals and choose how it
responds to them.
Another example of a program which catches and responds to these
signals is gdb. In fact any program designed to use ptrace is likely to
have a problem with this method of stopping and resuming tasks.
In contrast, the cgroup freezer uses the kernel freezer code to
prevent the freeze/unfreeze cycle from becoming visible to the tasks
being frozen. This allows the bash example above and gdb to run as
expected.
The freezer subsystem in the container filesystem defines a file named
freezer.state. Writing "FROZEN" to the state file will freeze all tasks in the
cgroup. Subsequently writing "THAWED" will unfreeze the tasks in the cgroup.
Reading will return the current state.
* Examples of usage :
# mkdir /containers/freezer
# mount -t cgroup -ofreezer freezer /containers
# mkdir /containers/0
# echo $some_pid > /containers/0/tasks
to get status of the freezer subsystem :
# cat /containers/0/freezer.state
THAWED
to freeze all tasks in the container :
# echo FROZEN > /containers/0/freezer.state
# cat /containers/0/freezer.state
FREEZING
# cat /containers/0/freezer.state
FROZEN
to unfreeze all tasks in the container :
# echo THAWED > /containers/0/freezer.state
# cat /containers/0/freezer.state
THAWED
This is the basic mechanism which should do the right thing for user space task
in a simple scenario.
It's important to note that freezing can be incomplete. In that case we return
EBUSY. This means that some tasks in the cgroup are busy doing something that
prevents us from completely freezing the cgroup at this time. After EBUSY,
the cgroup will remain partially frozen -- reflected by freezer.state reporting
"FREEZING" when read. The state will remain "FREEZING" until one of these
things happens:
1) Userspace cancels the freezing operation by writing "THAWED" to
the freezer.state file
2) Userspace retries the freezing operation by writing "FROZEN" to
the freezer.state file (writing "FREEZING" is not legal
and returns EIO)
3) The tasks that blocked the cgroup from entering the "FROZEN"
state disappear from the cgroup's set of tasks.

24
Documentation/controllers/memory.txt
View File

@ -112,14 +112,22 @@ the per cgroup LRU.
2.2.1 Accounting details
All mapped pages (RSS) and unmapped user pages (Page Cache) are accounted.
RSS pages are accounted at the time of page_add_*_rmap() unless they've already
been accounted for earlier. A file page will be accounted for as Page Cache;
it's mapped into the page tables of a process, duplicate accounting is carefully
avoided. Page Cache pages are accounted at the time of add_to_page_cache().
The corresponding routines that remove a page from the page tables or removes
a page from Page Cache is used to decrement the accounting counters of the
cgroup.
All mapped anon pages (RSS) and cache pages (Page Cache) are accounted.
(some pages which never be reclaimable and will not be on global LRU
are not accounted. we just accounts pages under usual vm management.)
RSS pages are accounted at page_fault unless they've already been accounted
for earlier. A file page will be accounted for as Page Cache when it's
inserted into inode (radix-tree). While it's mapped into the page tables of
processes, duplicate accounting is carefully avoided.
A RSS page is unaccounted when it's fully unmapped. A PageCache page is
unaccounted when it's removed from radix-tree.
At page migration, accounting information is kept.
Note: we just account pages-on-lru because our purpose is to control amount
of used pages. not-on-lru pages are tend to be out-of-control from vm view.
2.3 Shared Page Accounting

10
Documentation/cpu-freq/index.txt
View File

@ -35,11 +35,9 @@ Mailing List
------------
There is a CPU frequency changing CVS commit and general list where
you can report bugs, problems or submit patches. To post a message,
send an email to cpufreq@lists.linux.org.uk, to subscribe go to
http://lists.linux.org.uk/mailman/listinfo/cpufreq. Previous post to the
mailing list are available to subscribers at
http://lists.linux.org.uk/mailman/private/cpufreq/.
send an email to cpufreq@vger.kernel.org, to subscribe go to
http://vger.kernel.org/vger-lists.html#cpufreq and follow the
instructions there.
Links
-----
@ -50,7 +48,7 @@ how to access the CVS repository:
* http://cvs.arm.linux.org.uk/
the CPUFreq Mailing list:
* http://lists.linux.org.uk/mailman/listinfo/cpufreq
* http://vger.kernel.org/vger-lists.html#cpufreq
Clock and voltage scaling for the SA-1100:
* http://www.lartmaker.nl/projects/scaling

2
Documentation/cpusets.txt
View File

@ -48,7 +48,7 @@ hooks, beyond what is already present, required to manage dynamic
job placement on large systems.
Cpusets use the generic cgroup subsystem described in
Documentation/cgroup.txt.
Documentation/cgroups/cgroups.txt.
Requests by a task, using the sched_setaffinity(2) system call to
include CPUs in its CPU affinity mask, and using the mbind(2) and

2
Documentation/cris/README
View File

@ -27,7 +27,7 @@ operating system.
The ETRAX 100LX chip
--------------------
For reference, plase see the press-release:
For reference, please see the press-release:
http://www.axis.com/news/us/001101_etrax.htm

274
Documentation/development-process/1.Intro Normal file
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@ -0,0 +1,274 @@
1: A GUIDE TO THE KERNEL DEVELOPMENT PROCESS
The purpose of this document is to help developers (and their managers)
work with the development community with a minimum of frustration. It is
an attempt to document how this community works in a way which is
accessible to those who are not intimately familiar with Linux kernel
development (or, indeed, free software development in general). While
there is some technical material here, this is very much a process-oriented
discussion which does not require a deep knowledge of kernel programming to
understand.
1.1: EXECUTIVE SUMMARY
The rest of this section covers the scope of the kernel development process
and the kinds of frustrations that developers and their employers can
encounter there. There are a great many reasons why kernel code should be
merged into the official ("mainline") kernel, including automatic
availability to users, community support in many forms, and the ability to
influence the direction of kernel development. Code contributed to the
Linux kernel must be made available under a GPL-compatible license.
Section 2 introduces the development process, the kernel release cycle, and
the mechanics of the merge window. The various phases in the patch
development, review, and merging cycle are covered. There is some
discussion of tools and mailing lists. Developers wanting to get started
with kernel development are encouraged to track down and fix bugs as an
initial exercise.
Section 3 covers early-stage project planning, with an emphasis on
involving the development community as soon as possible.
Section 4 is about the coding process; several pitfalls which have been
encountered by other developers are discussed. Some requirements for
patches are covered, and there is an introduction to some of the tools
which can help to ensure that kernel patches are correct.
Section 5 talks about the process of posting patches for review. To be
taken seriously by the development community, patches must be properly
formatted and described, and they must be sent to the right place.
Following the advice in this section should help to ensure the best
possible reception for your work.
Section 6 covers what happens after posting patches; the job is far from
done at that point. Working with reviewers is a crucial part of the
development process; this section offers a number of tips on how to avoid
problems at this important stage. Developers are cautioned against
assuming that the job is done when a patch is merged into the mainline.
Section 7 introduces a couple of "advanced" topics: managing patches with
git and reviewing patches posted by others.
Section 8 concludes the document with pointers to sources for more
information on kernel development.
1.2: WHAT THIS DOCUMENT IS ABOUT
The Linux kernel, at over 6 million lines of code and well over 1000 active
contributors, is one of the largest and most active free software projects
in existence. Since its humble beginning in 1991, this kernel has evolved
into a best-of-breed operating system component which runs on pocket-sized
digital music players, desktop PCs, the largest supercomputers in
existence, and all types of systems in between. It is a robust, efficient,
and scalable solution for almost any situation.
With the growth of Linux has come an increase in the number of developers
(and companies) wishing to participate in its development. Hardware
vendors want to ensure that Linux supports their products well, making
those products attractive to Linux users. Embedded systems vendors, who
use Linux as a component in an integrated product, want Linux to be as
capable and well-suited to the task at hand as possible. Distributors and
other software vendors who base their products on Linux have a clear
interest in the capabilities, performance, and reliability of the Linux
kernel. And end users, too, will often wish to change Linux to make it
better suit their needs.
One of the most compelling features of Linux is that it is accessible to
these developers; anybody with the requisite skills can improve Linux and
influence the direction of its development. Proprietary products cannot
offer this kind of openness, which is a characteristic of the free software
process. But, if anything, the kernel is even more open than most other
free software projects. A typical three-month kernel development cycle can
involve over 1000 developers working for more than 100 different companies
(or for no company at all).
Working with the kernel development community is not especially hard. But,
that notwithstanding, many potential contributors have experienced
difficulties when trying to do kernel work. The kernel community has
evolved its own distinct ways of operating which allow it to function
smoothly (and produce a high-quality product) in an environment where
thousands of lines of code are being changed every day. So it is not
surprising that Linux kernel development process differs greatly from
proprietary development methods.
The kernel's development process may come across as strange and
intimidating to new developers, but there are good reasons and solid
experience behind it. A developer who does not understand the kernel
community's ways (or, worse, who tries to flout or circumvent them) will
have a frustrating experience in store. The development community, while
being helpful to those who are trying to learn, has little time for those
who will not listen or who do not care about the development process.
It is hoped that those who read this document will be able to avoid that
frustrating experience. There is a lot of material here, but the effort
involved in reading it will be repaid in short order. The development
community is always in need of developers who will help to make the kernel
better; the following text should help you - or those who work for you -
join our community.
1.3: CREDITS
This document was written by Jonathan Corbet, corbet@lwn.net. It has been
improved by comments from Johannes Berg, James Berry, Alex Chiang, Roland
Dreier, Randy Dunlap, Jake Edge, Jiri Kosina, Matt Mackall, Arthur Marsh,
Amanda McPherson, Andrew Morton, Andrew Price, Tsugikazu Shibata, and
Jochen Voß.
This work was supported by the Linux Foundation; thanks especially to
Amanda McPherson, who saw the value of this effort and made it all happen.
1.4: THE IMPORTANCE OF GETTING CODE INTO THE MAINLINE
Some companies and developers occasionally wonder why they should bother
learning how to work with the kernel community and get their code into the
mainline kernel (the "mainline" being the kernel maintained by Linus
Torvalds and used as a base by Linux distributors). In the short term,
contributing code can look like an avoidable expense; it seems easier to
just keep the code separate and support users directly. The truth of the
matter is that keeping code separate ("out of tree") is a false economy.
As a way of illustrating the costs of out-of-tree code, here are a few
relevant aspects of the kernel development process; most of these will be
discussed in greater detail later in this document. Consider:
- Code which has been merged into the mainline kernel is available to all
Linux users. It will automatically be present on all distributions which
enable it. There is no need for driver disks, downloads, or the hassles
of supporting multiple versions of multiple distributions; it all just
works, for the developer and for the user. Incorporation into the
mainline solves a large number of distribution and support problems.
- While kernel developers strive to maintain a stable interface to user
space, the internal kernel API is in constant flux. The lack of a stable
internal interface is a deliberate design decision; it allows fundamental
improvements to be made at any time and results in higher-quality code.
But one result of that policy is that any out-of-tree code requires
constant upkeep if it is to work with new kernels. Maintaining
out-of-tree code requires significant amounts of work just to keep that
code working.
Code which is in the mainline, instead, does not require this work as the
result of a simple rule requiring any developer who makes an API change
to also fix any code that breaks as the result of that change. So code
which has been merged into the mainline has significantly lower
maintenance costs.
- Beyond that, code which is in the kernel will often be improved by other
developers. Surprising results can come from empowering your user
community and customers to improve your product.
- Kernel code is subjected to review, both before and after merging into
the mainline. No matter how strong the original developer's skills are,
this review process invariably finds ways in which the code can be
improved. Often review finds severe bugs and security problems. This is
especially true for code which has been developed in a closed
environment; such code benefits strongly from review by outside
developers. Out-of-tree code is lower-quality code.
- Participation in the development process is your way to influence the
direction of kernel development. Users who complain from the sidelines
are heard, but active developers have a stronger voice - and the ability
to implement changes which make the kernel work better for their needs.
- When code is maintained separately, the possibility that a third party
will contribute a different implementation of a similar feature always
exists. Should that happen, getting your code merged will become much
harder - to the point of impossibility. Then you will be faced with the
unpleasant alternatives of either (1) maintaining a nonstandard feature
out of tree indefinitely, or (2) abandoning your code and migrating your
users over to the in-tree version.
- Contribution of code is the fundamental action which makes the whole
process work. By contributing your code you can add new functionality to
the kernel and provide capabilities and examples which are of use to
other kernel developers. If you have developed code for Linux (or are
thinking about doing so), you clearly have an interest in the continued
success of this platform; contributing code is one of the best ways to
help ensure that success.
All of the reasoning above applies to any out-of-tree kernel code,
including code which is distributed in proprietary, binary-only form.
There are, however, additional factors which should be taken into account
before considering any sort of binary-only kernel code distribution. These
include:
- The legal issues around the distribution of proprietary kernel modules
are cloudy at best; quite a few kernel copyright holders believe that
most binary-only modules are derived products of the kernel and that, as
a result, their distribution is a violation of the GNU General Public
license (about which more will be said below). Your author is not a
lawyer, and nothing in this document can possibly be considered to be
legal advice. The true legal status of closed-source modules can only be
determined by the courts. But the uncertainty which haunts those modules
is there regardless.
- Binary modules greatly increase the difficulty of debugging kernel
problems, to the point that most kernel developers will not even try. So
the distribution of binary-only modules will make it harder for your
users to get support from the community.
- Support is also harder for distributors of binary-only modules, who must
provide a version of the module for every distribution and every kernel
version they wish to support. Dozens of builds of a single module can
be required to provide reasonably comprehensive coverage, and your users
will have to upgrade your module separately every time they upgrade their
kernel.
- Everything that was said above about code review applies doubly to
closed-source code. Since this code is not available at all, it cannot
have been reviewed by the community and will, beyond doubt, have serious
problems.
Makers of embedded systems, in particular, may be tempted to disregard much
of what has been said in this section in the belief that they are shipping
a self-contained product which uses a frozen kernel version and requires no
more development after its release. This argument misses the value of
widespread code review and the value of allowing your users to add
capabilities to your product. But these products, too, have a limited
commercial life, after which a new version must be released. At that
point, vendors whose code is in the mainline and well maintained will be
much better positioned to get the new product ready for market quickly.
1.5: LICENSING
Code is contributed to the Linux kernel under a number of licenses, but all
code must be compatible with version 2 of the GNU General Public License
(GPLv2), which is the license covering the kernel distribution as a whole.
In practice, that means that all code contributions are covered either by
GPLv2 (with, optionally, language allowing distribution under later
versions of the GPL) or the three-clause BSD license. Any contributions
which are not covered by a compatible license will not be accepted into the
kernel.
Copyright assignments are not required (or requested) for code contributed
to the kernel. All code merged into the mainline kernel retains its
original ownership; as a result, the kernel now has thousands of owners.
One implication of this ownership structure is that any attempt to change
the licensing of the kernel is doomed to almost certain failure. There are
few practical scenarios where the agreement of all copyright holders could
be obtained (or their code removed from the kernel). So, in particular,
there is no prospect of a migration to version 3 of the GPL in the
foreseeable future.
It is imperative that all code contributed to the kernel be legitimately
free software. For that reason, code from anonymous (or pseudonymous)
contributors will not be accepted. All contributors are required to "sign
off" on their code, stating that the code can be distributed with the
kernel under the GPL. Code which has not been licensed as free software by
its owner, or which risks creating copyright-related problems for the
kernel (such as code which derives from reverse-engineering efforts lacking
proper safeguards) cannot be contributed.
Questions about copyright-related issues are common on Linux development
mailing lists. Such questions will normally receive no shortage of
answers, but one should bear in mind that the people answering those
questions are not lawyers and cannot provide legal advice. If you have
legal questions relating to Linux source code, there is no substitute for
talking with a lawyer who understands this field. Relying on answers
obtained on technical mailing lists is a risky affair.

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2: HOW THE DEVELOPMENT PROCESS WORKS
Linux kernel development in the early 1990's was a pretty loose affair,
with relatively small numbers of users and developers involved. With a
user base in the millions and with some 2,000 developers involved over the
course of one year, the kernel has since had to evolve a number of
processes to keep development happening smoothly. A solid understanding of
how the process works is required in order to be an effective part of it.
2.1: THE BIG PICTURE
The kernel developers use a loosely time-based release process, with a new
major kernel release happening every two or three months. The recent
release history looks like this:
2.6.26 July 13, 2008
2.6.25 April 16, 2008
2.6.24 January 24, 2008
2.6.23 October 9, 2007
2.6.22 July 8, 2007
2.6.21 April 25, 2007
2.6.20 February 4, 2007
Every 2.6.x release is a major kernel release with new features, internal
API changes, and more. A typical 2.6 release can contain over 10,000
changesets with changes to several hundred thousand lines of code. 2.6 is
thus the leading edge of Linux kernel development; the kernel uses a
rolling development model which is continually integrating major changes.
A relatively straightforward discipline is followed with regard to the
merging of patches for each release. At the beginning of each development
cycle, the "merge window" is said to be open. At that time, code which is
deemed to be sufficiently stable (and which is accepted by the development
community) is merged into the mainline kernel. The bulk of changes for a
new development cycle (and all of the major changes) will be merged during
this time, at a rate approaching 1,000 changes ("patches," or "changesets")
per day.
(As an aside, it is worth noting that the changes integrated during the
merge window do not come out of thin air; they have been collected, tested,
and staged ahead of time. How that process works will be described in
detail later on).
The merge window lasts for two weeks. At the end of this time, Linus
Torvalds will declare that the window is closed and release the first of
the "rc" kernels. For the kernel which is destined to be 2.6.26, for
example, the release which happens at the end of the merge window will be
called 2.6.26-rc1. The -rc1 release is the signal that the time to merge
new features has passed, and that the time to stabilize the next kernel has
begun.
Over the next six to ten weeks, only patches which fix problems should be
submitted to the mainline. On occasion a more significant change will be
allowed, but such occasions are rare; developers who try to merge new
features outside of the merge window tend to get an unfriendly reception.
As a general rule, if you miss the merge window for a given feature, the
best thing to do is to wait for the next development cycle. (An occasional
exception is made for drivers for previously-unsupported hardware; if they
touch no in-tree code, they cannot cause regressions and should be safe to
add at any time).
As fixes make their way into the mainline, the patch rate will slow over
time. Linus releases new -rc kernels about once a week; a normal series
will get up to somewhere between -rc6 and -rc9 before the kernel is
considered to be sufficiently stable and the final 2.6.x release is made.
At that point the whole process starts over again.
As an example, here is how the 2.6.25 development cycle went (all dates in
2008):
January 24 2.6.24 stable release
February 10 2.6.25-rc1, merge window closes
February 15 2.6.25-rc2
February 24 2.6.25-rc3
March 4 2.6.25-rc4
March 9 2.6.25-rc5
March 16 2.6.25-rc6
March 25 2.6.25-rc7
April 1 2.6.25-rc8
April 11 2.6.25-rc9
April 16 2.6.25 stable release
How do the developers decide when to close the development cycle and create
the stable release? The most significant metric used is the list of
regressions from previous releases. No bugs are welcome, but those which
break systems which worked in the past are considered to be especially
serious. For this reason, patches which cause regressions are looked upon
unfavorably and are quite likely to be reverted during the stabilization
period.
The developers' goal is to fix all known regressions before the stable
release is made. In the real world, this kind of perfection is hard to
achieve; there are just too many variables in a project of this size.
There comes a point where delaying the final release just makes the problem
worse; the pile of changes waiting for the next merge window will grow
larger, creating even more regressions the next time around. So most 2.6.x
kernels go out with a handful of known regressions though, hopefully, none
of them are serious.
Once a stable release is made, its ongoing maintenance is passed off to the
"stable team," currently comprised of Greg Kroah-Hartman and Chris Wright.
The stable team will release occasional updates to the stable release using
the 2.6.x.y numbering scheme. To be considered for an update release, a
patch must (1) fix a significant bug, and (2) already be merged into the
mainline for the next development kernel. Continuing our 2.6.25 example,
the history (as of this writing) is:
May 1 2.6.25.1
May 6 2.6.25.2
May 9 2.6.25.3
May 15 2.6.25.4
June 7 2.6.25.5
June 9 2.6.25.6
June 16 2.6.25.7
June 21 2.6.25.8
June 24 2.6.25.9
Stable updates for a given kernel are made for approximately six months;
after that, the maintenance of stable releases is solely the responsibility
of the distributors which have shipped that particular kernel.
2.2: THE LIFECYCLE OF A PATCH
Patches do not go directly from the developer's keyboard into the mainline
kernel. There is, instead, a somewhat involved (if somewhat informal)
process designed to ensure that each patch is reviewed for quality and that
each patch implements a change which is desirable to have in the mainline.
This process can happen quickly for minor fixes, or, in the case of large
and controversial changes, go on for years. Much developer frustration
comes from a lack of understanding of this process or from attempts to
circumvent it.
In the hopes of reducing that frustration, this document will describe how
a patch gets into the kernel. What follows below is an introduction which
describes the process in a somewhat idealized way. A much more detailed
treatment will come in later sections.
The stages that a patch goes through are, generally:
- Design. This is where the real requirements for the patch - and the way
those requirements will be met - are laid out. Design work is often
done without involving the community, but it is better to do this work
in the open if at all possible; it can save a lot of time redesigning
things later.
- Early review. Patches are posted to the relevant mailing list, and
developers on that list reply with any comments they may have. This
process should turn up any major problems with a patch if all goes
well.
- Wider review. When the patch is getting close to ready for mainline
inclusion, it will be accepted by a relevant subsystem maintainer -
though this acceptance is not a guarantee that the patch will make it
all the way to the mainline. The patch will show up in the maintainer's
subsystem tree and into the staging trees (described below). When the
process works, this step leads to more extensive review of the patch and
the discovery of any problems resulting from the integration of this
patch with work being done by others.
- Merging into the mainline. Eventually, a successful patch will be
merged into the mainline repository managed by Linus Torvalds. More
comments and/or problems may surface at this time; it is important that
the developer be responsive to these and fix any issues which arise.
- Stable release. The number of users potentially affected by the patch
is now large, so, once again, new problems may arise.
- Long-term maintenance. While it is certainly possible for a developer
to forget about code after merging it, that sort of behavior tends to
leave a poor impression in the development community. Merging code
eliminates some of the maintenance burden, in that others will fix
problems caused by API changes. But the original developer should
continue to take responsibility for the code if it is to remain useful
in the longer term.
One of the largest mistakes made by kernel developers (or their employers)
is to try to cut the process down to a single "merging into the mainline"
step. This approach invariably leads to frustration for everybody
involved.
2.3: HOW PATCHES GET INTO THE KERNEL
There is exactly one person who can merge patches into the mainline kernel
repository: Linus Torvalds. But, of the over 12,000 patches which went
into the 2.6.25 kernel, only 250 (around 2%) were directly chosen by Linus
himself. The kernel project has long since grown to a size where no single
developer could possibly inspect and select every patch unassisted. The
way the kernel developers have addressed this growth is through the use of
a lieutenant system built around a chain of trust.
The kernel code base is logically broken down into a set of subsystems:
networking, specific architecture support, memory management, video
devices, etc. Most subsystems have a designated maintainer, a developer
who has overall responsibility for the code within that subsystem. These
subsystem maintainers are the gatekeepers (in a loose way) for the portion
of the kernel they manage; they are the ones who will (usually) accept a
patch for inclusion into the mainline kernel.
Subsystem maintainers each manage their own version of the kernel source
tree, usually (but certainly not always) using the git source management
tool. Tools like git (and related tools like quilt or mercurial) allow
maintainers to track a list of patches, including authorship information
and other metadata. At any given time, the maintainer can identify which
patches in his or her repository are not found in the mainline.
When the merge window opens, top-level maintainers will ask Linus to "pull"
the patches they have selected for merging from their repositories. If
Linus agrees, the stream of patches will flow up into his repository,
becoming part of the mainline kernel. The amount of attention that Linus
pays to specific patches received in a pull operation varies. It is clear
that, sometimes, he looks quite closely. But, as a general rule, Linus
trusts the subsystem maintainers to not send bad patches upstream.
Subsystem maintainers, in turn, can pull patches from other maintainers.
For example, the networking tree is built from patches which accumulated
first in trees dedicated to network device drivers, wireless networking,
etc. This chain of repositories can be arbitrarily long, though it rarely
exceeds two or three links. Since each maintainer in the chain trusts
those managing lower-level trees, this process is known as the "chain of
trust."
Clearly, in a system like this, getting patches into the kernel depends on
finding the right maintainer. Sending patches directly to Linus is not
normally the right way to go.
2.4: STAGING TREES
The chain of subsystem trees guides the flow of patches into the kernel,
but it also raises an interesting question: what if somebody wants to look
at all of the patches which are being prepared for the next merge window?
Developers will be interested in what other changes are pending to see
whether there are any conflicts to worry about; a patch which changes a
core kernel function prototype, for example, will conflict with any other
patches which use the older form of that function. Reviewers and testers
want access to the changes in their integrated form before all of those
changes land in the mainline kernel. One could pull changes from all of
the interesting subsystem trees, but that would be a big and error-prone
job.
The answer comes in the form of staging trees, where subsystem trees are
collected for testing and review. The older of these trees, maintained by
Andrew Morton, is called "-mm" (for memory management, which is how it got
started). The -mm tree integrates patches from a long list of subsystem
trees; it also has some patches aimed at helping with debugging.
Beyond that, -mm contains a significant collection of patches which have
been selected by Andrew directly. These patches may have been posted on a
mailing list, or they may apply to a part of the kernel for which there is
no designated subsystem tree. As a result, -mm operates as a sort of
subsystem tree of last resort; if there is no other obvious path for a
patch into the mainline, it is likely to end up in -mm. Miscellaneous
patches which accumulate in -mm will eventually either be forwarded on to
an appropriate subsystem tree or be sent directly to Linus. In a typical
development cycle, approximately 10% of the patches going into the mainline
get there via -mm.
The current -mm patch can always be found from the front page of
http://kernel.org/
Those who want to see the current state of -mm can get the "-mm of the
moment" tree, found at:
http://userweb.kernel.org/~akpm/mmotm/
Use of the MMOTM tree is likely to be a frustrating experience, though;
there is a definite chance that it will not even compile.
The other staging tree, started more recently, is linux-next, maintained by
Stephen Rothwell. The linux-next tree is, by design, a snapshot of what
the mainline is expected to look like after the next merge window closes.
Linux-next trees are announced on the linux-kernel and linux-next mailing
lists when they are assembled; they can be downloaded from:
http://www.kernel.org/pub/linux/kernel/people/sfr/linux-next/
Some information about linux-next has been gathered at:
http://linux.f-seidel.de/linux-next/pmwiki/
How the linux-next tree will fit into the development process is still
changing. As of this writing, the first full development cycle involving
linux-next (2.6.26) is coming to an end; thus far, it has proved to be a
valuable resource for finding and fixing integration problems before the
beginning of the merge window. See http://lwn.net/Articles/287155/ for
more information on how linux-next has worked to set up the 2.6.27 merge
window.
Some developers have begun to suggest that linux-next should be used as the
target for future development as well. The linux-next tree does tend to be
far ahead of the mainline and is more representative of the tree into which
any new work will be merged. The downside to this idea is that the
volatility of linux-next tends to make it a difficult development target.
See http://lwn.net/Articles/289013/ for more information on this topic, and
stay tuned; much is still in flux where linux-next is involved.
2.5: TOOLS
As can be seen from the above text, the kernel development process depends
heavily on the ability to herd collections of patches in various
directions. The whole thing would not work anywhere near as well as it
does without suitably powerful tools. Tutorials on how to use these tools
are well beyond the scope of this document, but there is space for a few
pointers.
By far the dominant source code management system used by the kernel
community is git. Git is one of a number of distributed version control
systems being developed in the free software community. It is well tuned
for kernel development, in that it performs quite well when dealing with
large repositories and large numbers of patches. It also has a reputation
for being difficult to learn and use, though it has gotten better over
time. Some sort of familiarity with git is almost a requirement for kernel
developers; even if they do not use it for their own work, they'll need git
to keep up with what other developers (and the mainline) are doing.
Git is now packaged by almost all Linux distributions. There is a home
page at
http://git.or.cz/
That page has pointers to documentation and tutorials. One should be
aware, in particular, of the Kernel Hacker's Guide to git, which has
information specific to kernel development:
http://linux.yyz.us/git-howto.html
Among the kernel developers who do not use git, the most popular choice is
almost certainly Mercurial:
http://www.selenic.com/mercurial/
Mercurial shares many features with git, but it provides an interface which
many find easier to use.
The other tool worth knowing about is Quilt:
http://savannah.nongnu.org/projects/quilt/
Quilt is a patch management system, rather than a source code management
system. It does not track history over time; it is, instead, oriented
toward tracking a specific set of changes against an evolving code base.
Some major subsystem maintainers use quilt to manage patches intended to go
upstream. For the management of certain kinds of trees (-mm, for example),
quilt is the best tool for the job.
2.6: MAILING LISTS
A great deal of Linux kernel development work is done by way of mailing
lists. It is hard to be a fully-functioning member of the community
without joining at least one list somewhere. But Linux mailing lists also
represent a potential hazard to developers, who risk getting buried under a
load of electronic mail, running afoul of the conventions used on the Linux
lists, or both.
Most kernel mailing lists are run on vger.kernel.org; the master list can
be found at:
http://vger.kernel.org/vger-lists.html
There are lists hosted elsewhere, though; a number of them are at
lists.redhat.com.
The core mailing list for kernel development is, of course, linux-kernel.
This list is an intimidating place to be; volume can reach 500 messages per
day, the amount of noise is high, the conversation can be severely
technical, and participants are not always concerned with showing a high
degree of politeness. But there is no other place where the kernel
development community comes together as a whole; developers who avoid this
list will miss important information.
There are a few hints which can help with linux-kernel survival:
- Have the list delivered to a separate folder, rather than your main
mailbox. One must be able to ignore the stream for sustained periods of
time.
- Do not try to follow every conversation - nobody else does. It is
important to filter on both the topic of interest (though note that
long-running conversations can drift away from the original subject
without changing the email subject line) and the people who are
participating.
- Do not feed the trolls. If somebody is trying to stir up an angry
response, ignore them.
- When responding to linux-kernel email (or that on other lists) preserve
the Cc: header for all involved. In the absence of a strong reason (such
as an explicit request), you should never remove recipients. Always make
sure that the person you are responding to is in the Cc: list. This
convention also makes it unnecessary to explicitly ask to be copied on
replies to your postings.
- Search the list archives (and the net as a whole) before asking
questions. Some developers can get impatient with people who clearly
have not done their homework.
- Avoid top-posting (the practice of putting your answer above the quoted
text you are responding to). It makes your response harder to read and
makes a poor impression.
- Ask on the correct mailing list. Linux-kernel may be the general meeting
point, but it is not the best place to find developers from all
subsystems.
The last point - finding the correct mailing list - is a common place for
beginning developers to go wrong. Somebody who asks a networking-related
question on linux-kernel will almost certainly receive a polite suggestion
to ask on the netdev list instead, as that is the list frequented by most
networking developers. Other lists exist for the SCSI, video4linux, IDE,
filesystem, etc. subsystems. The best place to look for mailing lists is
in the MAINTAINERS file packaged with the kernel source.
2.7: GETTING STARTED WITH KERNEL DEVELOPMENT
Questions about how to get started with the kernel development process are
common - from both individuals and companies. Equally common are missteps
which make the beginning of the relationship harder than it has to be.
Companies often look to hire well-known developers to get a development
group started. This can, in fact, be an effective technique. But it also
tends to be expensive and does not do much to grow the pool of experienced
kernel developers. It is possible to bring in-house developers up to speed
on Linux kernel development, given the investment of a bit of time. Taking
this time can endow an employer with a group of developers who understand
the kernel and the company both, and who can help to train others as well.
Over the medium term, this is often the more profitable approach.
Individual developers are often, understandably, at a loss for a place to
start. Beginning with a large project can be intimidating; one often wants
to test the waters with something smaller first. This is the point where
some developers jump into the creation of patches fixing spelling errors or
minor coding style issues. Unfortunately, such patches create a level of
noise which is distracting for the development community as a whole, so,
increasingly, they are looked down upon. New developers wishing to
introduce themselves to the community will not get the sort of reception
they wish for by these means.
Andrew Morton gives this advice for aspiring kernel developers
The #1 project for all kernel beginners should surely be "make sure
that the kernel runs perfectly at all times on all machines which
you can lay your hands on". Usually the way to do this is to work
with others on getting things fixed up (this can require
persistence!) but that's fine - it's a part of kernel development.
(http://lwn.net/Articles/283982/).
In the absence of obvious problems to fix, developers are advised to look
at the current lists of regressions and open bugs in general. There is
never any shortage of issues in need of fixing; by addressing these issues,
developers will gain experience with the process while, at the same time,
building respect with the rest of the development community.

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3: EARLY-STAGE PLANNING
When contemplating a Linux kernel development project, it can be tempting
to jump right in and start coding. As with any significant project,
though, much of the groundwork for success is best laid before the first
line of code is written. Some time spent in early planning and
communication can save far more time later on.
3.1: SPECIFYING THE PROBLEM
Like any engineering project, a successful kernel enhancement starts with a
clear description of the problem to be solved. In some cases, this step is
easy: when a driver is needed for a specific piece of hardware, for
example. In others, though, it is tempting to confuse the real problem
with the proposed solution, and that can lead to difficulties.
Consider an example: some years ago, developers working with Linux audio
sought a way to run applications without dropouts or other artifacts caused
by excessive latency in the system. The solution they arrived at was a
kernel module intended to hook into the Linux Security Module (LSM)
framework; this module could be configured to give specific applications
access to the realtime scheduler. This module was implemented and sent to
the linux-kernel mailing list, where it immediately ran into problems.
To the audio developers, this security module was sufficient to solve their
immediate problem. To the wider kernel community, though, it was seen as a
misuse of the LSM framework (which is not intended to confer privileges
onto processes which they would not otherwise have) and a risk to system
stability. Their preferred solutions involved realtime scheduling access
via the rlimit mechanism for the short term, and ongoing latency reduction
work in the long term.
The audio community, however, could not see past the particular solution
they had implemented; they were unwilling to accept alternatives. The
resulting disagreement left those developers feeling disillusioned with the
entire kernel development process; one of them went back to an audio list
and posted this:
There are a number of very good Linux kernel developers, but they
tend to get outshouted by a large crowd of arrogant fools. Trying
to communicate user requirements to these people is a waste of
time. They are much too "intelligent" to listen to lesser mortals.
(http://lwn.net/Articles/131776/).
The reality of the situation was different; the kernel developers were far
more concerned about system stability, long-term maintenance, and finding
the right solution to the problem than they were with a specific module.
The moral of the story is to focus on the problem - not a specific solution
- and to discuss it with the development community before investing in the
creation of a body of code.
So, when contemplating a kernel development project, one should obtain
answers to a short set of questions:
- What, exactly, is the problem which needs to be solved?
- Who are the users affected by this problem? Which use cases should the
solution address?
- How does the kernel fall short in addressing that problem now?
Only then does it make sense to start considering possible solutions.
3.2: EARLY DISCUSSION
When planning a kernel development project, it makes great sense to hold
discussions with the community before launching into implementation. Early
communication can save time and trouble in a number of ways:
- It may well be that the problem is addressed by the kernel in ways which
you have not understood. The Linux kernel is large and has a number of
features and capabilities which are not immediately obvious. Not all
kernel capabilities are documented as well as one might like, and it is
easy to miss things. Your author has seen the posting of a complete
driver which duplicated an existing driver that the new author had been
unaware of. Code which reinvents existing wheels is not only wasteful;
it will also not be accepted into the mainline kernel.
- There may be elements of the proposed solution which will not be
acceptable for mainline merging. It is better to find out about
problems like this before writing the code.
- It's entirely possible that other developers have thought about the
problem; they may have ideas for a better solution, and may be willing
to help in the creation of that solution.
Years of experience with the kernel development community have taught a
clear lesson: kernel code which is designed and developed behind closed
doors invariably has problems which are only revealed when the code is
released into the community. Sometimes these problems are severe,
requiring months or years of effort before the code can be brought up to
the kernel community's standards. Some examples include:
- The Devicescape network stack was designed and implemented for
single-processor systems. It could not be merged into the mainline
until it was made suitable for multiprocessor systems. Retrofitting
locking and such into code is a difficult task; as a result, the merging
of this code (now called mac80211) was delayed for over a year.
- The Reiser4 filesystem included a number of capabilities which, in the
core kernel developers' opinion, should have been implemented in the
virtual filesystem layer instead. It also included features which could
not easily be implemented without exposing the system to user-caused
deadlocks. The late revelation of these problems - and refusal to
address some of them - has caused Reiser4 to stay out of the mainline
kernel.
- The AppArmor security module made use of internal virtual filesystem
data structures in ways which were considered to be unsafe and
unreliable. This code has since been significantly reworked, but
remains outside of the mainline.
In each of these cases, a great deal of pain and extra work could have been
avoided with some early discussion with the kernel developers.
3.3: WHO DO YOU TALK TO?
When developers decide to take their plans public, the next question will
be: where do we start? The answer is to find the right mailing list(s) and
the right maintainer. For mailing lists, the best approach is to look in
the MAINTAINERS file for a relevant place to post. If there is a suitable
subsystem list, posting there is often preferable to posting on
linux-kernel; you are more likely to reach developers with expertise in the
relevant subsystem and the environment may be more supportive.
Finding maintainers can be a bit harder. Again, the MAINTAINERS file is
the place to start. That file tends to not always be up to date, though,
and not all subsystems are represented there. The person listed in the
MAINTAINERS file may, in fact, not be the person who is actually acting in
that role currently. So, when there is doubt about who to contact, a
useful trick is to use git (and "git log" in particular) to see who is
currently active within the subsystem of interest. Look at who is writing
patches, and who, if anybody, is attaching Signed-off-by lines to those
patches. Those are the people who will be best placed to help with a new
development project.
If all else fails, talking to Andrew Morton can be an effective way to
track down a maintainer for a specific piece of code.
3.4: WHEN TO POST?
If possible, posting your plans during the early stages can only be
helpful. Describe the problem being solved and any plans that have been
made on how the implementation will be done. Any information you can
provide can help the development community provide useful input on the
project.
One discouraging thing which can happen at this stage is not a hostile
reaction, but, instead, little or no reaction at all. The sad truth of the
matter is (1) kernel developers tend to be busy, (2) there is no shortage
of people with grand plans and little code (or even prospect of code) to
back them up, and (3) nobody is obligated to review or comment on ideas
posted by others. If a request-for-comments posting yields little in the
way of comments, do not assume that it means there is no interest in the
project. Unfortunately, you also cannot assume that there are no problems
with your idea. The best thing to do in this situation is to proceed,
keeping the community informed as you go.
3.5: GETTING OFFICIAL BUY-IN
If your work is being done in a corporate environment - as most Linux
kernel work is - you must, obviously, have permission from suitably
empowered managers before you can post your company's plans or code to a
public mailing list. The posting of code which has not been cleared for
release under a GPL-compatible license can be especially problematic; the
sooner that a company's management and legal staff can agree on the posting
of a kernel development project, the better off everybody involved will be.
Some readers may be thinking at this point that their kernel work is
intended to support a product which does not yet have an officially
acknowledged existence. Revealing their employer's plans on a public
mailing list may not be a viable option. In cases like this, it is worth
considering whether the secrecy is really necessary; there is often no real
need to keep development plans behind closed doors.
That said, there are also cases where a company legitimately cannot
disclose its plans early in the development process. Companies with
experienced kernel developers may choose to proceed in an open-loop manner
on the assumption that they will be able to avoid serious integration
problems later. For companies without that sort of in-house expertise, the
best option is often to hire an outside developer to review the plans under
a non-disclosure agreement. The Linux Foundation operates an NDA program
designed to help with this sort of situation; more information can be found
at:
http://www.linuxfoundation.org/en/NDA_program
This kind of review is often enough to avoid serious problems later on
without requiring public disclosure of the project.

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4: GETTING THE CODE RIGHT
While there is much to be said for a solid and community-oriented design
process, the proof of any kernel development project is in the resulting
code. It is the code which will be examined by other developers and merged
(or not) into the mainline tree. So it is the quality of this code which
will determine the ultimate success of the project.
This section will examine the coding process. We'll start with a look at a
number of ways in which kernel developers can go wrong. Then the focus
will shift toward doing things right and the tools which can help in that
quest.
4.1: PITFALLS
* Coding style
The kernel has long had a standard coding style, described in
Documentation/CodingStyle. For much of that time, the policies described
in that file were taken as being, at most, advisory. As a result, there is
a substantial amount of code in the kernel which does not meet the coding
style guidelines. The presence of that code leads to two independent
hazards for kernel developers.
The first of these is to believe that the kernel coding standards do not
matter and are not enforced. The truth of the matter is that adding new
code to the kernel is very difficult if that code is not coded according to
the standard; many developers will request that the code be reformatted
before they will even review it. A code base as large as the kernel
requires some uniformity of code to make it possible for developers to
quickly understand any part of it. So there is no longer room for
strangely-formatted code.
Occasionally, the kernel's coding style will run into conflict with an
employer's mandated style. In such cases, the kernel's style will have to
win before the code can be merged. Putting code into the kernel means
giving up a degree of control in a number of ways - including control over
how the code is formatted.
The other trap is to assume that code which is already in the kernel is
urgently in need of coding style fixes. Developers may start to generate
reformatting patches as a way of gaining familiarity with the process, or
as a way of getting their name into the kernel changelogs - or both. But
pure coding style fixes are seen as noise by the development community;
they tend to get a chilly reception. So this type of patch is best
avoided. It is natural to fix the style of a piece of code while working
on it for other reasons, but coding style changes should not be made for
their own sake.
The coding style document also should not be read as an absolute law which
can never be transgressed. If there is a good reason to go against the
style (a line which becomes far less readable if split to fit within the
80-column limit, for example), just do it.
* Abstraction layers
Computer Science professors teach students to make extensive use of
abstraction layers in the name of flexibility and information hiding.
Certainly the kernel makes extensive use of abstraction; no project
involving several million lines of code could do otherwise and survive.
But experience has shown that excessive or premature abstraction can be
just as harmful as premature optimization. Abstraction should be used to
the level required and no further.
At a simple level, consider a function which has an argument which is
always passed as zero by all callers. One could retain that argument just
in case somebody eventually needs to use the extra flexibility that it
provides. By that time, though, chances are good that the code which
implements this extra argument has been broken in some subtle way which was
never noticed - because it has never been used. Or, when the need for
extra flexibility arises, it does not do so in a way which matches the
programmer's early expectation. Kernel developers will routinely submit
patches to remove unused arguments; they should, in general, not be added
in the first place.
Abstraction layers which hide access to hardware - often to allow the bulk
of a driver to be used with multiple operating systems - are especially
frowned upon. Such layers obscure the code and may impose a performance
penalty; they do not belong in the Linux kernel.
On the other hand, if you find yourself copying significant amounts of code
from another kernel subsystem, it is time to ask whether it would, in fact,
make sense to pull out some of that code into a separate library or to
implement that functionality at a higher level. There is no value in
replicating the same code throughout the kernel.
* #ifdef and preprocessor use in general
The C preprocessor seems to present a powerful temptation to some C
programmers, who see it as a way to efficiently encode a great deal of
flexibility into a source file. But the preprocessor is not C, and heavy
use of it results in code which is much harder for others to read and
harder for the compiler to check for correctness. Heavy preprocessor use
is almost always a sign of code which needs some cleanup work.
Conditional compilation with #ifdef is, indeed, a powerful feature, and it
is used within the kernel. But there is little desire to see code which is
sprinkled liberally with #ifdef blocks. As a general rule, #ifdef use
should be confined to header files whenever possible.
Conditionally-compiled code can be confined to functions which, if the code
is not to be present, simply become empty. The compiler will then quietly
optimize out the call to the empty function. The result is far cleaner
code which is easier to follow.
C preprocessor macros present a number of hazards, including possible
multiple evaluation of expressions with side effects and no type safety.
If you are tempted to define a macro, consider creating an inline function
instead. The code which results will be the same, but inline functions are
easier to read, do not evaluate their arguments multiple times, and allow
the compiler to perform type checking on the arguments and return value.
* Inline functions
Inline functions present a hazard of their own, though. Programmers can
become enamored of the perceived efficiency inherent in avoiding a function
call and fill a source file with inline functions. Those functions,
however, can actually reduce performance. Since their code is replicated
at each call site, they end up bloating the size of the compiled kernel.
That, in turn, creates pressure on the processor's memory caches, which can
slow execution dramatically. Inline functions, as a rule, should be quite
small and relatively rare. The cost of a function call, after all, is not
that high; the creation of large numbers of inline functions is a classic
example of premature optimization.
In general, kernel programmers ignore cache effects at their peril. The
classic time/space tradeoff taught in beginning data structures classes
often does not apply to contemporary hardware. Space *is* time, in that a
larger program will run slower than one which is more compact.
* Locking
In May, 2006, the "Devicescape" networking stack was, with great
fanfare, released under the GPL and made available for inclusion in the
mainline kernel. This donation was welcome news; support for wireless
networking in Linux was considered substandard at best, and the Devicescape
stack offered the promise of fixing that situation. Yet, this code did not
actually make it into the mainline until June, 2007 (2.6.22). What
happened?
This code showed a number of signs of having been developed behind
corporate doors. But one large problem in particular was that it was not
designed to work on multiprocessor systems. Before this networking stack
(now called mac80211) could be merged, a locking scheme needed to be
retrofitted onto it.
Once upon a time, Linux kernel code could be developed without thinking
about the concurrency issues presented by multiprocessor systems. Now,
however, this document is being written on a dual-core laptop. Even on
single-processor systems, work being done to improve responsiveness will
raise the level of concurrency within the kernel. The days when kernel
code could be written without thinking about locking are long past.
Any resource (data structures, hardware registers, etc.) which could be
accessed concurrently by more than one thread must be protected by a lock.
New code should be written with this requirement in mind; retrofitting
locking after the fact is a rather more difficult task. Kernel developers
should take the time to understand the available locking primitives well
enough to pick the right tool for the job. Code which shows a lack of
attention to concurrency will have a difficult path into the mainline.
* Regressions
One final hazard worth mentioning is this: it can be tempting to make a
change (which may bring big improvements) which causes something to break
for existing users. This kind of change is called a "regression," and
regressions have become most unwelcome in the mainline kernel. With few
exceptions, changes which cause regressions will be backed out if the
regression cannot be fixed in a timely manner. Far better to avoid the
regression in the first place.
It is often argued that a regression can be justified if it causes things
to work for more people than it creates problems for. Why not make a
change if it brings new functionality to ten systems for each one it
breaks? The best answer to this question was expressed by Linus in July,
2007:
So we don't fix bugs by introducing new problems. That way lies
madness, and nobody ever knows if you actually make any real
progress at all. Is it two steps forwards, one step back, or one
step forward and two steps back?
(http://lwn.net/Articles/243460/).
An especially unwelcome type of regression is any sort of change to the
user-space ABI. Once an interface has been exported to user space, it must
be supported indefinitely. This fact makes the creation of user-space
interfaces particularly challenging: since they cannot be changed in
incompatible ways, they must be done right the first time. For this
reason, a great deal of thought, clear documentation, and wide review for
user-space interfaces is always required.
4.2: CODE CHECKING TOOLS
For now, at least, the writing of error-free code remains an ideal that few
of us can reach. What we can hope to do, though, is to catch and fix as
many of those errors as possible before our code goes into the mainline
kernel. To that end, the kernel developers have put together an impressive
array of tools which can catch a wide variety of obscure problems in an
automated way. Any problem caught by the computer is a problem which will
not afflict a user later on, so it stands to reason that the automated
tools should be used whenever possible.
The first step is simply to heed the warnings produced by the compiler.
Contemporary versions of gcc can detect (and warn about) a large number of
potential errors. Quite often, these warnings point to real problems.
Code submitted for review should, as a rule, not produce any compiler
warnings. When silencing warnings, take care to understand the real cause
and try to avoid "fixes" which make the warning go away without addressing
its cause.
Note that not all compiler warnings are enabled by default. Build the
kernel with "make EXTRA_CFLAGS=-W" to get the full set.
The kernel provides several configuration options which turn on debugging
features; most of these are found in the "kernel hacking" submenu. Several
of these options should be turned on for any kernel used for development or
testing purposes. In particular, you should turn on:
- ENABLE_WARN_DEPRECATED, ENABLE_MUST_CHECK, and FRAME_WARN to get an
extra set of warnings for problems like the use of deprecated interfaces
or ignoring an important return value from a function. The output
generated by these warnings can be verbose, but one need not worry about
warnings from other parts of the kernel.
- DEBUG_OBJECTS will add code to track the lifetime of various objects
created by the kernel and warn when things are done out of order. If
you are adding a subsystem which creates (and exports) complex objects
of its own, consider adding support for the object debugging
infrastructure.
- DEBUG_SLAB can find a variety of memory allocation and use errors; it
should be used on most development kernels.
- DEBUG_SPINLOCK, DEBUG_SPINLOCK_SLEEP, and DEBUG_MUTEXES will find a
number of common locking errors.
There are quite a few other debugging options, some of which will be
discussed below. Some of them have a significant performance impact and
should not be used all of the time. But some time spent learning the
available options will likely be paid back many times over in short order.
One of the heavier debugging tools is the locking checker, or "lockdep."
This tool will track the acquisition and release of every lock (spinlock or
mutex) in the system, the order in which locks are acquired relative to
each other, the current interrupt environment, and more. It can then
ensure that locks are always acquired in the same order, that the same
interrupt assumptions apply in all situations, and so on. In other words,
lockdep can find a number of scenarios in which the system could, on rare
occasion, deadlock. This kind of problem can be painful (for both
developers and users) in a deployed system; lockdep allows them to be found
in an automated manner ahead of time. Code with any sort of non-trivial
locking should be run with lockdep enabled before being submitted for
inclusion.
As a diligent kernel programmer, you will, beyond doubt, check the return
status of any operation (such as a memory allocation) which can fail. The
fact of the matter, though, is that the resulting failure recovery paths
are, probably, completely untested. Untested code tends to be broken code;
you could be much more confident of your code if all those error-handling
paths had been exercised a few times.
The kernel provides a fault injection framework which can do exactly that,
especially where memory allocations are involved. With fault injection
enabled, a configurable percentage of memory allocations will be made to
fail; these failures can be restricted to a specific range of code.
Running with fault injection enabled allows the programmer to see how the
code responds when things go badly. See
Documentation/fault-injection/fault-injection.text for more information on
how to use this facility.
Other kinds of errors can be found with the "sparse" static analysis tool.
With sparse, the programmer can be warned about confusion between
user-space and kernel-space addresses, mixture of big-endian and
small-endian quantities, the passing of integer values where a set of bit
flags is expected, and so on. Sparse must be installed separately (it can
be found at http://www.kernel.org/pub/software/devel/sparse/ if your
distributor does not package it); it can then be run on the code by adding
"C=1" to your make command.
Other kinds of portability errors are best found by compiling your code for
other architectures. If you do not happen to have an S/390 system or a
Blackfin development board handy, you can still perform the compilation
step. A large set of cross compilers for x86 systems can be found at
http://www.kernel.org/pub/tools/crosstool/
Some time spent installing and using these compilers will help avoid
embarrassment later.
4.3: DOCUMENTATION
Documentation has often been more the exception than the rule with kernel
development. Even so, adequate documentation will help to ease the merging
of new code into the kernel, make life easier for other developers, and
will be helpful for your users. In many cases, the addition of
documentation has become essentially mandatory.
The first piece of documentation for any patch is its associated
changelog. Log entries should describe the problem being solved, the form
of the solution, the people who worked on the patch, any relevant
effects on performance, and anything else that might be needed to
understand the patch.
Any code which adds a new user-space interface - including new sysfs or
/proc files - should include documentation of that interface which enables
user-space developers to know what they are working with. See
Documentation/ABI/README for a description of how this documentation should
be formatted and what information needs to be provided.
The file Documentation/kernel-parameters.txt describes all of the kernel's
boot-time parameters. Any patch which adds new parameters should add the
appropriate entries to this file.
Any new configuration options must be accompanied by help text which
clearly explains the options and when the user might want to select them.
Internal API information for many subsystems is documented by way of
specially-formatted comments; these comments can be extracted and formatted
in a number of ways by the "kernel-doc" script. If you are working within
a subsystem which has kerneldoc comments, you should maintain them and add
them, as appropriate, for externally-available functions. Even in areas
which have not been so documented, there is no harm in adding kerneldoc
comments for the future; indeed, this can be a useful activity for
beginning kernel developers. The format of these comments, along with some
information on how to create kerneldoc templates can be found in the file
Documentation/kernel-doc-nano-HOWTO.txt.
Anybody who reads through a significant amount of existing kernel code will
note that, often, comments are most notable by their absence. Once again,
the expectations for new code are higher than they were in the past;
merging uncommented code will be harder. That said, there is little desire
for verbosely-commented code. The code should, itself, be readable, with
comments explaining the more subtle aspects.
Certain things should always be commented. Uses of memory barriers should
be accompanied by a line explaining why the barrier is necessary. The
locking rules for data structures generally need to be explained somewhere.
Major data structures need comprehensive documentation in general.
Non-obvious dependencies between separate bits of code should be pointed
out. Anything which might tempt a code janitor to make an incorrect
"cleanup" needs a comment saying why it is done the way it is. And so on.
4.4: INTERNAL API CHANGES
The binary interface provided by the kernel to user space cannot be broken
except under the most severe circumstances. The kernel's internal
programming interfaces, instead, are highly fluid and can be changed when
the need arises. If you find yourself having to work around a kernel API,
or simply not using a specific functionality because it does not meet your
needs, that may be a sign that the API needs to change. As a kernel
developer, you are empowered to make such changes.
There are, of course, some catches. API changes can be made, but they need
to be well justified. So any patch making an internal API change should be
accompanied by a description of what the change is and why it is
necessary. This kind of change should also be broken out into a separate
patch, rather than buried within a larger patch.
The other catch is that a developer who changes an internal API is
generally charged with the task of fixing any code within the kernel tree
which is broken by the change. For a widely-used function, this duty can
lead to literally hundreds or thousands of changes - many of which are
likely to conflict with work being done by other developers. Needless to
say, this can be a large job, so it is best to be sure that the
justification is solid.
When making an incompatible API change, one should, whenever possible,
ensure that code which has not been updated is caught by the compiler.
This will help you to be sure that you have found all in-tree uses of that
interface. It will also alert developers of out-of-tree code that there is
a change that they need to respond to. Supporting out-of-tree code is not
something that kernel developers need to be worried about, but we also do
not have to make life harder for out-of-tree developers than it it needs to
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5: POSTING PATCHES
Sooner or later, the time comes when your work is ready to be presented to
the community for review and, eventually, inclusion into the mainline
kernel. Unsurprisingly, the kernel development community has evolved a set
of conventions and procedures which are used in the posting of patches;
following them will make life much easier for everybody involved. This
document will attempt to cover these expectations in reasonable detail;
more information can also be found in the files SubmittingPatches,
SubmittingDrivers, and SubmitChecklist in the kernel documentation
directory.
5.1: WHEN TO POST
There is a constant temptation to avoid posting patches before they are
completely "ready." For simple patches, that is not a problem. If the
work being done is complex, though, there is a lot to be gained by getting
feedback from the community before the work is complete. So you should
consider posting in-progress work, or even making a git tree available so
that interested developers can catch up with your work at any time.
When posting code which is not yet considered ready for inclusion, it is a
good idea to say so in the posting itself. Also mention any major work
which remains to be done and any known problems. Fewer people will look at
patches which are known to be half-baked, but those who do will come in
with the idea that they can help you drive the work in the right direction.
5.2: BEFORE CREATING PATCHES
There are a number of things which should be done before you consider
sending patches to the development community. These include:
- Test the code to the extent that you can. Make use of the kernel's
debugging tools, ensure that the kernel will build with all reasonable
combinations of configuration options, use cross-compilers to build for
different architectures, etc.
- Make sure your code is compliant with the kernel coding style
guidelines.
- Does your change have performance implications? If so, you should run
benchmarks showing what the impact (or benefit) of your change is; a
summary of the results should be included with the patch.
- Be sure that you have the right to post the code. If this work was done
for an employer, the employer likely has a right to the work and must be
agreeable with its release under the GPL.
As a general rule, putting in some extra thought before posting code almost
always pays back the effort in short order.
5.3: PATCH PREPARATION
The preparation of patches for posting can be a surprising amount of work,
but, once again, attempting to save time here is not generally advisable
even in the short term.
Patches must be prepared against a specific version of the kernel. As a
general rule, a patch should be based on the current mainline as found in
Linus's git tree. It may become necessary to make versions against -mm,
linux-next, or a subsystem tree, though, to facilitate wider testing and
review. Depending on the area of your patch and what is going on
elsewhere, basing a patch against these other trees can require a
significant amount of work resolving conflicts and dealing with API
changes.
Only the most simple changes should be formatted as a single patch;
everything else should be made as a logical series of changes. Splitting
up patches is a bit of an art; some developers spend a long time figuring
out how to do it in the way that the community expects. There are a few
rules of thumb, however, which can help considerably:
- The patch series you post will almost certainly not be the series of
changes found in your working revision control system. Instead, the
changes you have made need to be considered in their final form, then
split apart in ways which make sense. The developers are interested in
discrete, self-contained changes, not the path you took to get to those
changes.
- Each logically independent change should be formatted as a separate
patch. These changes can be small ("add a field to this structure") or
large (adding a significant new driver, for example), but they should be
conceptually small and amenable to a one-line description. Each patch
should make a specific change which can be reviewed on its own and
verified to do what it says it does.
- As a way of restating the guideline above: do not mix different types of
changes in the same patch. If a single patch fixes a critical security
bug, rearranges a few structures, and reformats the code, there is a
good chance that it will be passed over and the important fix will be
lost.
- Each patch should yield a kernel which builds and runs properly; if your
patch series is interrupted in the middle, the result should still be a
working kernel. Partial application of a patch series is a common
scenario when the "git bisect" tool is used to find regressions; if the
result is a broken kernel, you will make life harder for developers and
users who are engaging in the noble work of tracking down problems.
- Do not overdo it, though. One developer recently posted a set of edits
to a single file as 500 separate patches - an act which did not make him
the most popular person on the kernel mailing list. A single patch can
be reasonably large as long as it still contains a single *logical*
change.
- It can be tempting to add a whole new infrastructure with a series of
patches, but to leave that infrastructure unused until the final patch
in the series enables the whole thing. This temptation should be
avoided if possible; if that series adds regressions, bisection will
finger the last patch as the one which caused the problem, even though
the real bug is elsewhere. Whenever possible, a patch which adds new
code should make that code active immediately.
Working to create the perfect patch series can be a frustrating process
which takes quite a bit of time and thought after the "real work" has been
done. When done properly, though, it is time well spent.
5.4: PATCH FORMATTING
So now you have a perfect series of patches for posting, but the work is
not done quite yet. Each patch needs to be formatted into a message which
quickly and clearly communicates its purpose to the rest of the world. To
that end, each patch will be composed of the following:
- An optional "From" line naming the author of the patch. This line is
only necessary if you are passing on somebody else's patch via email,
but it never hurts to add it when in doubt.
- A one-line description of what the patch does. This message should be
enough for a reader who sees it with no other context to figure out the
scope of the patch; it is the line that will show up in the "short form"
changelogs. This message is usually formatted with the relevant
subsystem name first, followed by the purpose of the patch. For
example:
gpio: fix build on CONFIG_GPIO_SYSFS=n
- A blank line followed by a detailed description of the contents of the
patch. This description can be as long as is required; it should say
what the patch does and why it should be applied to the kernel.
- One or more tag lines, with, at a minimum, one Signed-off-by: line from
the author of the patch. Tags will be described in more detail below.
The above three items should, normally, be the text used when committing
the change to a revision control system. They are followed by:
- The patch itself, in the unified ("-u") patch format. Using the "-p"
option to diff will associate function names with changes, making the
resulting patch easier for others to read.
You should avoid including changes to irrelevant files (those generated by
the build process, for example, or editor backup files) in the patch. The
file "dontdiff" in the Documentation directory can help in this regard;
pass it to diff with the "-X" option.
The tags mentioned above are used to describe how various developers have
been associated with the development of this patch. They are described in
detail in the SubmittingPatches document; what follows here is a brief
summary. Each of these lines has the format:
tag: Full Name <email address> optional-other-stuff
The tags in common use are:
- Signed-off-by: this is a developer's certification that he or she has
the right to submit the patch for inclusion into the kernel. It is an
agreement to the Developer's Certificate of Origin, the full text of
which can be found in Documentation/SubmittingPatches. Code without a
proper signoff cannot be merged into the mainline.
- Acked-by: indicates an agreement by another developer (often a
maintainer of the relevant code) that the patch is appropriate for
inclusion into the kernel.
- Tested-by: states that the named person has tested the patch and found
it to work.
- Reviewed-by: the named developer has reviewed the patch for correctness;
see the reviewer's statement in Documentation/SubmittingPatches for more
detail.
- Reported-by: names a user who reported a problem which is fixed by this
patch; this tag is used to give credit to the (often underappreciated)
people who test our code and let us know when things do not work
correctly.
- Cc: the named person received a copy of the patch and had the
opportunity to comment on it.
Be careful in the addition of tags to your patches: only Cc: is appropriate
for addition without the explicit permission of the person named.
5.5: SENDING THE PATCH
Before you mail your patches, there are a couple of other things you should
take care of:
- Are you sure that your mailer will not corrupt the patches? Patches
which have had gratuitous white-space changes or line wrapping performed
by the mail client will not apply at the other end, and often will not
be examined in any detail. If there is any doubt at all, mail the patch
to yourself and convince yourself that it shows up intact.
Documentation/email-clients.txt has some helpful hints on making
specific mail clients work for sending patches.
- Are you sure your patch is free of silly mistakes? You should always
run patches through scripts/checkpatch.pl and address the complaints it
comes up with. Please bear in mind that checkpatch.pl, while being the
embodiment of a fair amount of thought about what kernel patches should
look like, is not smarter than you. If fixing a checkpatch.pl complaint
would make the code worse, don't do it.
Patches should always be sent as plain text. Please do not send them as
attachments; that makes it much harder for reviewers to quote sections of
the patch in their replies. Instead, just put the patch directly into your
message.
When mailing patches, it is important to send copies to anybody who might
be interested in it. Unlike some other projects, the kernel encourages
people to err on the side of sending too many copies; don't assume that the
relevant people will see your posting on the mailing lists. In particular,
copies should go to:
- The maintainer(s) of the affected subsystem(s). As described earlier,
the MAINTAINERS file is the first place to look for these people.
- Other developers who have been working in the same area - especially
those who might be working there now. Using git to see who else has
modified the files you are working on can be helpful.
- If you are responding to a bug report or a feature request, copy the
original poster as well.
- Send a copy to the relevant mailing list, or, if nothing else applies,
the linux-kernel list.
- If you are fixing a bug, think about whether the fix should go into the
next stable update. If so, stable@kernel.org should get a copy of the
patch. Also add a "Cc: stable@kernel.org" to the tags within the patch
itself; that will cause the stable team to get a notification when your
fix goes into the mainline.
When selecting recipients for a patch, it is good to have an idea of who
you think will eventually accept the patch and get it merged. While it
is possible to send patches directly to Linus Torvalds and have him merge
them, things are not normally done that way. Linus is busy, and there are
subsystem maintainers who watch over specific parts of the kernel. Usually
you will be wanting that maintainer to merge your patches. If there is no
obvious maintainer, Andrew Morton is often the patch target of last resort.
Patches need good subject lines. The canonical format for a patch line is
something like:
[PATCH nn/mm] subsys: one-line description of the patch
where "nn" is the ordinal number of the patch, "mm" is the total number of
patches in the series, and "subsys" is the name of the affected subsystem.
Clearly, nn/mm can be omitted for a single, standalone patch.
If you have a significant series of patches, it is customary to send an
introductory description as part zero. This convention is not universally
followed though; if you use it, remember that information in the
introduction does not make it into the kernel changelogs. So please ensure
that the patches, themselves, have complete changelog information.
In general, the second and following parts of a multi-part patch should be
sent as a reply to the first part so that they all thread together at the
receiving end. Tools like git and quilt have commands to mail out a set of
patches with the proper threading. If you have a long series, though, and
are using git, please provide the --no-chain-reply-to option to avoid
creating exceptionally deep nesting.

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6: FOLLOWTHROUGH
At this point, you have followed the guidelines given so far and, with the
addition of your own engineering skills, have posted a perfect series of
patches. One of the biggest mistakes that even experienced kernel
developers can make is to conclude that their work is now done. In truth,
posting patches indicates a transition into the next stage of the process,
with, possibly, quite a bit of work yet to be done.
It is a rare patch which is so good at its first posting that there is no
room for improvement. The kernel development process recognizes this fact,
and, as a result, is heavily oriented toward the improvement of posted
code. You, as the author of that code, will be expected to work with the
kernel community to ensure that your code is up to the kernel's quality
standards. A failure to participate in this process is quite likely to
prevent the inclusion of your patches into the mainline.
6.1: WORKING WITH REVIEWERS
A patch of any significance will result in a number of comments from other
developers as they review the code. Working with reviewers can be, for
many developers, the most intimidating part of the kernel development
process. Life can be made much easier, though, if you keep a few things in
mind:
- If you have explained your patch well, reviewers will understand its
value and why you went to the trouble of writing it. But that value
will not keep them from asking a fundamental question: what will it be
like to maintain a kernel with this code in it five or ten years later?
Many of the changes you may be asked to make - from coding style tweaks
to substantial rewrites - come from the understanding that Linux will
still be around and under development a decade from now.
- Code review is hard work, and it is a relatively thankless occupation;
people remember who wrote kernel code, but there is little lasting fame
for those who reviewed it. So reviewers can get grumpy, especially when
they see the same mistakes being made over and over again. If you get a
review which seems angry, insulting, or outright offensive, resist the
impulse to respond in kind. Code review is about the code, not about
the people, and code reviewers are not attacking you personally.
- Similarly, code reviewers are not trying to promote their employers'
agendas at the expense of your own. Kernel developers often expect to
be working on the kernel years from now, but they understand that their
employer could change. They truly are, almost without exception,
working toward the creation of the best kernel they can; they are not
trying to create discomfort for their employers' competitors.
What all of this comes down to is that, when reviewers send you comments,
you need to pay attention to the technical observations that they are
making. Do not let their form of expression or your own pride keep that
from happening. When you get review comments on a patch, take the time to
understand what the reviewer is trying to say. If possible, fix the things
that the reviewer is asking you to fix. And respond back to the reviewer:
thank them, and describe how you will answer their questions.
Note that you do not have to agree with every change suggested by
reviewers. If you believe that the reviewer has misunderstood your code,
explain what is really going on. If you have a technical objection to a
suggested change, describe it and justify your solution to the problem. If
your explanations make sense, the reviewer will accept them. Should your
explanation not prove persuasive, though, especially if others start to
agree with the reviewer, take some time to think things over again. It can
be easy to become blinded by your own solution to a problem to the point
that you don't realize that something is fundamentally wrong or, perhaps,
you're not even solving the right problem.
One fatal mistake is to ignore review comments in the hope that they will
go away. They will not go away. If you repost code without having
responded to the comments you got the time before, you're likely to find
that your patches go nowhere.
Speaking of reposting code: please bear in mind that reviewers are not
going to remember all the details of the code you posted the last time
around. So it is always a good idea to remind reviewers of previously
raised issues and how you dealt with them; the patch changelog is a good
place for this kind of information. Reviewers should not have to search
through list archives to familiarize themselves with what was said last
time; if you help them get a running start, they will be in a better mood
when they revisit your code.
What if you've tried to do everything right and things still aren't going
anywhere? Most technical disagreements can be resolved through discussion,
but there are times when somebody simply has to make a decision. If you
honestly believe that this decision is going against you wrongly, you can
always try appealing to a higher power. As of this writing, that higher
power tends to be Andrew Morton. Andrew has a great deal of respect in the
kernel development community; he can often unjam a situation which seems to
be hopelessly blocked. Appealing to Andrew should not be done lightly,
though, and not before all other alternatives have been explored. And bear
in mind, of course, that he may not agree with you either.
6.2: WHAT HAPPENS NEXT
If a patch is considered to be a good thing to add to the kernel, and once
most of the review issues have been resolved, the next step is usually
entry into a subsystem maintainer's tree. How that works varies from one
subsystem to the next; each maintainer has his or her own way of doing
things. In particular, there may be more than one tree - one, perhaps,
dedicated to patches planned for the next merge window, and another for
longer-term work.
For patches applying to areas for which there is no obvious subsystem tree
(memory management patches, for example), the default tree often ends up
being -mm. Patches which affect multiple subsystems can also end up going
through the -mm tree.
Inclusion into a subsystem tree can bring a higher level of visibility to a
patch. Now other developers working with that tree will get the patch by
default. Subsystem trees typically feed into -mm and linux-next as well,
making their contents visible to the development community as a whole. At
this point, there's a good chance that you will get more comments from a
new set of reviewers; these comments need to be answered as in the previous
round.
What may also happen at this point, depending on the nature of your patch,
is that conflicts with work being done by others turn up. In the worst
case, heavy patch conflicts can result in some work being put on the back
burner so that the remaining patches can be worked into shape and merged.
Other times, conflict resolution will involve working with the other
developers and, possibly, moving some patches between trees to ensure that
everything applies cleanly. This work can be a pain, but count your
blessings: before the advent of the linux-next tree, these conflicts often
only turned up during the merge window and had to be addressed in a hurry.
Now they can be resolved at leisure, before the merge window opens.
Some day, if all goes well, you'll log on and see that your patch has been
merged into the mainline kernel. Congratulations! Once the celebration is
complete (and you have added yourself to the MAINTAINERS file), though, it
is worth remembering an important little fact: the job still is not done.
Merging into the mainline brings its own challenges.
To begin with, the visibility of your patch has increased yet again. There
may be a new round of comments from developers who had not been aware of
the patch before. It may be tempting to ignore them, since there is no
longer any question of your code being merged. Resist that temptation,
though; you still need to be responsive to developers who have questions or
suggestions.
More importantly, though: inclusion into the mainline puts your code into
the hands of a much larger group of testers. Even if you have contributed
a driver for hardware which is not yet available, you will be surprised by
how many people will build your code into their kernels. And, of course,
where there are testers, there will be bug reports.
The worst sort of bug reports are regressions. If your patch causes a
regression, you'll find an uncomfortable number of eyes upon you;
regressions need to be fixed as soon as possible. If you are unwilling or
unable to fix the regression (and nobody else does it for you), your patch
will almost certainly be removed during the stabilization period. Beyond
negating all of the work you have done to get your patch into the mainline,
having a patch pulled as the result of a failure to fix a regression could
well make it harder for you to get work merged in the future.
After any regressions have been dealt with, there may be other, ordinary
bugs to deal with. The stabilization period is your best opportunity to
fix these bugs and ensure that your code's debut in a mainline kernel
release is as solid as possible. So, please, answer bug reports, and fix
the problems if at all possible. That's what the stabilization period is
for; you can start creating cool new patches once any problems with the old
ones have been taken care of.
And don't forget that there are other milestones which may also create bug
reports: the next mainline stable release, when prominent distributors pick
up a version of the kernel containing your patch, etc. Continuing to
respond to these reports is a matter of basic pride in your work. If that
is insufficient motivation, though, it's also worth considering that the
development community remembers developers who lose interest in their code
after it's merged. The next time you post a patch, they will be evaluating
it with the assumption that you will not be around to maintain it
afterward.
6.3: OTHER THINGS THAT CAN HAPPEN
One day, you may open your mail client and see that somebody has mailed you
a patch to your code. That is one of the advantages of having your code
out there in the open, after all. If you agree with the patch, you can
either forward it on to the subsystem maintainer (be sure to include a
proper From: line so that the attribution is correct, and add a signoff of
your own), or send an Acked-by: response back and let the original poster
send it upward.
If you disagree with the patch, send a polite response explaining why. If
possible, tell the author what changes need to be made to make the patch
acceptable to you. There is a certain resistance to merging patches which
are opposed by the author and maintainer of the code, but it only goes so
far. If you are seen as needlessly blocking good work, those patches will
eventually flow around you and get into the mainline anyway. In the Linux
kernel, nobody has absolute veto power over any code. Except maybe Linus.
On very rare occasion, you may see something completely different: another
developer posts a different solution to your problem. At that point,
chances are that one of the two patches will not be merged, and "mine was
here first" is not considered to be a compelling technical argument. If
somebody else's patch displaces yours and gets into the mainline, there is
really only one way to respond: be pleased that your problem got solved and
get on with your work. Having one's work shoved aside in this manner can
be hurtful and discouraging, but the community will remember your reaction
long after they have forgotten whose patch actually got merged.

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7: ADVANCED TOPICS
At this point, hopefully, you have a handle on how the development process
works. There is still more to learn, however! This section will cover a
number of topics which can be helpful for developers wanting to become a
regular part of the Linux kernel development process.
7.1: MANAGING PATCHES WITH GIT
The use of distributed version control for the kernel began in early 2002,
when Linus first started playing with the proprietary BitKeeper
application. While BitKeeper was controversial, the approach to software
version management it embodied most certainly was not. Distributed version
control enabled an immediate acceleration of the kernel development
project. In current times, there are several free alternatives to
BitKeeper. For better or for worse, the kernel project has settled on git
as its tool of choice.
Managing patches with git can make life much easier for the developer,
especially as the volume of those patches grows. Git also has its rough
edges and poses certain hazards; it is a young and powerful tool which is
still being civilized by its developers. This document will not attempt to
teach the reader how to use git; that would be sufficient material for a
long document in its own right. Instead, the focus here will be on how git
fits into the kernel development process in particular. Developers who
wish to come up to speed with git will find more information at:
http://git.or.cz/
http://www.kernel.org/pub/software/scm/git/docs/user-manual.html
and on various tutorials found on the web.
The first order of business is to read the above sites and get a solid
understanding of how git works before trying to use it to make patches
available to others. A git-using developer should be able to obtain a copy
of the mainline repository, explore the revision history, commit changes to
the tree, use branches, etc. An understanding of git's tools for the
rewriting of history (such as rebase) is also useful. Git comes with its
own terminology and concepts; a new user of git should know about refs,
remote branches, the index, fast-forward merges, pushes and pulls, detached
heads, etc. It can all be a little intimidating at the outset, but the
concepts are not that hard to grasp with a bit of study.
Using git to generate patches for submission by email can be a good
exercise while coming up to speed.
When you are ready to start putting up git trees for others to look at, you
will, of course, need a server that can be pulled from. Setting up such a
server with git-daemon is relatively straightforward if you have a system
which is accessible to the Internet. Otherwise, free, public hosting sites
(Github, for example) are starting to appear on the net. Established
developers can get an account on kernel.org, but those are not easy to come
by; see http://kernel.org/faq/ for more information.
The normal git workflow involves the use of a lot of branches. Each line
of development can be separated into a separate "topic branch" and
maintained independently. Branches in git are cheap, there is no reason to
not make free use of them. And, in any case, you should not do your
development in any branch which you intend to ask others to pull from.
Publicly-available branches should be created with care; merge in patches
from development branches when they are in complete form and ready to go -
not before.
Git provides some powerful tools which can allow you to rewrite your
development history. An inconvenient patch (one which breaks bisection,
say, or which has some other sort of obvious bug) can be fixed in place or
made to disappear from the history entirely. A patch series can be
rewritten as if it had been written on top of today's mainline, even though
you have been working on it for months. Changes can be transparently
shifted from one branch to another. And so on. Judicious use of git's
ability to revise history can help in the creation of clean patch sets with
fewer problems.
Excessive use of this capability can lead to other problems, though, beyond
a simple obsession for the creation of the perfect project history.
Rewriting history will rewrite the changes contained in that history,
turning a tested (hopefully) kernel tree into an untested one. But, beyond
that, developers cannot easily collaborate if they do not have a shared
view of the project history; if you rewrite history which other developers
have pulled into their repositories, you will make life much more difficult
for those developers. So a simple rule of thumb applies here: history
which has been exported to others should generally be seen as immutable
thereafter.
So, once you push a set of changes to your publicly-available server, those
changes should not be rewritten. Git will attempt to enforce this rule if
you try to push changes which do not result in a fast-forward merge
(i.e. changes which do not share the same history). It is possible to
override this check, and there may be times when it is necessary to rewrite
an exported tree. Moving changesets between trees to avoid conflicts in
linux-next is one example. But such actions should be rare. This is one
of the reasons why development should be done in private branches (which
can be rewritten if necessary) and only moved into public branches when
it's in a reasonably advanced state.
As the mainline (or other tree upon which a set of changes is based)
advances, it is tempting to merge with that tree to stay on the leading
edge. For a private branch, rebasing can be an easy way to keep up with
another tree, but rebasing is not an option once a tree is exported to the
world. Once that happens, a full merge must be done. Merging occasionally
makes good sense, but overly frequent merges can clutter the history
needlessly. Suggested technique in this case is to merge infrequently, and
generally only at specific release points (such as a mainline -rc
release). If you are nervous about specific changes, you can always
perform test merges in a private branch. The git "rerere" tool can be
useful in such situations; it remembers how merge conflicts were resolved
so that you don't have to do the same work twice.
One of the biggest recurring complaints about tools like git is this: the
mass movement of patches from one repository to another makes it easy to
slip in ill-advised changes which go into the mainline below the review
radar. Kernel developers tend to get unhappy when they see that kind of
thing happening; putting up a git tree with unreviewed or off-topic patches
can affect your ability to get trees pulled in the future. Quoting Linus:
You can send me patches, but for me to pull a git patch from you, I
need to know that you know what you're doing, and I need to be able
to trust things *without* then having to go and check every
individual change by hand.
(http://lwn.net/Articles/224135/).
To avoid this kind of situation, ensure that all patches within a given
branch stick closely to the associated topic; a "driver fixes" branch
should not be making changes to the core memory management code. And, most
importantly, do not use a git tree to bypass the review process. Post an
occasional summary of the tree to the relevant list, and, when the time is
right, request that the tree be included in linux-next.
If and when others start to send patches for inclusion into your tree,
don't forget to review them. Also ensure that you maintain the correct
authorship information; the git "am" tool does its best in this regard, but
you may have to add a "From:" line to the patch if it has been relayed to
you via a third party.
When requesting a pull, be sure to give all the relevant information: where
your tree is, what branch to pull, and what changes will result from the
pull. The git request-pull command can be helpful in this regard; it will
format the request as other developers expect, and will also check to be
sure that you have remembered to push those changes to the public server.
7.2: REVIEWING PATCHES
Some readers will certainly object to putting this section with "advanced
topics" on the grounds that even beginning kernel developers should be
reviewing patches. It is certainly true that there is no better way to
learn how to program in the kernel environment than by looking at code
posted by others. In addition, reviewers are forever in short supply; by
looking at code you can make a significant contribution to the process as a
whole.
Reviewing code can be an intimidating prospect, especially for a new kernel
developer who may well feel nervous about questioning code - in public -
which has been posted by those with more experience. Even code written by
the most experienced developers can be improved, though. Perhaps the best
piece of advice for reviewers (all reviewers) is this: phrase review
comments as questions rather than criticisms. Asking "how does the lock
get released in this path?" will always work better than stating "the
locking here is wrong."
Different developers will review code from different points of view. Some
are mostly concerned with coding style and whether code lines have trailing
white space. Others will focus primarily on whether the change implemented
by the patch as a whole is a good thing for the kernel or not. Yet others
will check for problematic locking, excessive stack usage, possible
security issues, duplication of code found elsewhere, adequate
documentation, adverse effects on performance, user-space ABI changes, etc.
All types of review, if they lead to better code going into the kernel, are
welcome and worthwhile.

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8: FOR MORE INFORMATION
There are numerous sources of information on Linux kernel development and
related topics. First among those will always be the Documentation
directory found in the kernel source distribution. The top-level HOWTO
file is an important starting point; SubmittingPatches and
SubmittingDrivers are also something which all kernel developers should
read. Many internal kernel APIs are documented using the kerneldoc
mechanism; "make htmldocs" or "make pdfdocs" can be used to generate those
documents in HTML or PDF format (though the version of TeX shipped by some
distributions runs into internal limits and fails to process the documents
properly).
Various web sites discuss kernel development at all levels of detail. Your
author would like to humbly suggest http://lwn.net/ as a source;
information on many specific kernel topics can be found via the LWN kernel
index at:
http://lwn.net/Kernel/Index/
Beyond that, a valuable resource for kernel developers is:
http://kernelnewbies.org/
Information about the linux-next tree gathers at:
http://linux.f-seidel.de/linux-next/pmwiki/
And, of course, one should not forget http://kernel.org/, the definitive
location for kernel release information.
There are a number of books on kernel development:
Linux Device Drivers, 3rd Edition (Jonathan Corbet, Alessandro
Rubini, and Greg Kroah-Hartman). Online at
http://lwn.net/Kernel/LDD3/.
Linux Kernel Development (Robert Love).
Understanding the Linux Kernel (Daniel Bovet and Marco Cesati).
All of these books suffer from a common fault, though: they tend to be
somewhat obsolete by the time they hit the shelves, and they have been on
the shelves for a while now. Still, there is quite a bit of good
information to be found there.
Documentation for git can be found at:
http://www.kernel.org/pub/software/scm/git/docs/
http://www.kernel.org/pub/software/scm/git/docs/user-manual.html
9: CONCLUSION
Congratulations to anybody who has made it through this long-winded
document. Hopefully it has provided a helpful understanding of how the
Linux kernel is developed and how you can participate in that process.
In the end, it's the participation that matters. Any open source software
project is no more than the sum of what its contributors put into it. The
Linux kernel has progressed as quickly and as well as it has because it has
been helped by an impressively large group of developers, all of whom are
working to make it better. The kernel is a premier example of what can be
done when thousands of people work together toward a common goal.
The kernel can always benefit from a larger developer base, though. There
is always more work to do. But, just as importantly, most other
participants in the Linux ecosystem can benefit through contributing to the
kernel. Getting code into the mainline is the key to higher code quality,
lower maintenance and distribution costs, a higher level of influence over
the direction of kernel development, and more. It is a situation where
everybody involved wins. Fire up your editor and come join us; you will be
more than welcome.

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160 = /dev/usb/legousbtower0 1st USB Legotower device
...
175 = /dev/usb/legousbtower15 16th USB Legotower device
176 = /dev/usb/usbtmc1 First USB TMC device
...
192 = /dev/usb/usbtmc16 16th USB TMC device
240 = /dev/usb/dabusb0 First daubusb device
...
243 = /dev/usb/dabusb3 Fourth dabusb device

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*.aux
*.bin
*.cpio
*.css
*.csp
*.dsp
*.dvi
*.elf
*.eps
*.fw.gen.S
*.fw
*.gen.S
*.gif
*.grep
*.grp
@ -30,6 +32,7 @@
*.s
*.sgml
*.so
*.so.dbg
*.symtypes
*.tab.c
*.tab.h
@ -38,24 +41,17 @@
*.xml
*_MODULES
*_vga16.c
*cscope*
*~
*.9
*.9.gz
.*
.cscope
.gitignore
.mailmap
.mm
53c700_d.h
53c8xx_d.h*
COPYING
CREDITS
CVS
ChangeSet
Image
Kerntypes
MODS.txt
Module.markers
Module.symvers
PENDING
SCCS
@ -73,7 +69,9 @@ autoconf.h*
bbootsect
bin2c
binkernel.spec
binoffset
bootsect
bounds.h
bsetup
btfixupprep
build
@ -89,39 +87,36 @@ config_data.h*
config_data.gz*
conmakehash
consolemap_deftbl.c*
cpustr.h
crc32table.h*
cscope.*
defkeymap.c*
defkeymap.c
devlist.h*
docproc
dummy_sym.c*
elf2ecoff
elfconfig.h*
filelist
fixdep
fore200e_mkfirm
fore200e_pca_fw.c*
gconf
gen-devlist
gen-kdb_cmds.c*
gen_crc32table
gen_init_cpio
genksyms
gentbl
*_gray256.c
ihex2fw
ikconfig.h*
initramfs_data.cpio
initramfs_data.cpio.gz
initramfs_list
kallsyms
kconfig
kconfig.tk
keywords.c*
keywords.c
ksym.c*
ksym.h*
kxgettext
lkc_defs.h
lex.c*
lex.c
lex.*.c
logo_*.c
logo_*_clut224.c
@ -130,7 +125,6 @@ lxdialog
mach-types
mach-types.h
machtypes.h
make_times_h
map
maui_boot.h
mconf
@ -138,6 +132,7 @@ miboot*
mk_elfconfig
mkboot
mkbugboot
mkcpustr
mkdep
mkprep
mktables
@ -145,11 +140,12 @@ mktree
modpost
modules.order
modversions.h*
ncscope.*
offset.h
offsets.h
oui.c*
parse.c*
parse.h*
parse.c
parse.h
patches*
pca200e.bin
pca200e_ecd.bin2
@ -157,7 +153,7 @@ piggy.gz
piggyback
pnmtologo
ppc_defs.h*
promcon_tbl.c*
promcon_tbl.c
pss_boot.h
qconf
raid6altivec*.c
@ -168,27 +164,38 @@ series
setup
setup.bin
setup.elf
sim710_d.h*
sImage
sm_tbl*
split-include
syscalltab.h
tags
tftpboot.img
timeconst.h
times.h*
tkparse
trix_boot.h
utsrelease.h*
vdso-syms.lds
vdso.lds
vdso32-int80-syms.lds
vdso32-syms.lds
vdso32-syscall-syms.lds
vdso32-sysenter-syms.lds
vdso32.lds
vdso32.so.dbg
vdso64.lds
vdso64.so.dbg
version.h*
vmlinux
vmlinux-*
vmlinux.aout
vmlinux*.lds*
vmlinux*.scr
vmlinux.lds
vsyscall.lds
vsyscall_32.lds
wanxlfw.inc
uImage
unifdef
wakeup.bin
wakeup.elf
wakeup.lds
zImage*
zconf.hash.c

1
Documentation/fb/intelfb.txt
View File

@ -14,6 +14,7 @@ graphics devices. These would include:
Intel 915GM
Intel 945G
Intel 945GM
Intel 945GME
Intel 965G
Intel 965GM

4
Documentation/fb/uvesafb.txt
View File

@ -52,7 +52,7 @@ are either given on the kernel command line or as module parameters, e.g.:
video=uvesafb:1024x768-32,mtrr:3,ywrap (compiled into the kernel)
# modprobe uvesafb mode=1024x768-32 mtrr=3 scroll=ywrap (module)
# modprobe uvesafb mode_option=1024x768-32 mtrr=3 scroll=ywrap (module)
Accepted options:
@ -105,7 +105,7 @@ vtotal:n
<mode> The mode you want to set, in the standard modedb format. Refer to
modedb.txt for a detailed description. When uvesafb is compiled as
a module, the mode string should be provided as a value of the
'mode' option.
'mode_option' option.
vbemode:x
Force the use of VBE mode x. The mode will only be set if it's

870
Documentation/fb/viafb.modes Normal file
View File

@ -0,0 +1,870 @@
#
#
# These data are based on the CRTC parameters in
#
# VIA Integration Graphics Chip
# (C) 2004 VIA Technologies Inc.
#
#
# 640x480, 60 Hz, Non-Interlaced (25.175 MHz dotclock)
#
# Horizontal Vertical
# Resolution 640 480
# Scan Frequency 31.469 kHz 59.94 Hz
# Sync Width 3.813 us 0.064 ms
# 12 chars 2 lines
# Front Porch 0.636 us 0.318 ms
# 2 chars 10 lines
# Back Porch 1.907 us 1.048 ms
# 6 chars 33 lines
# Active Time 25.422 us 15.253 ms
# 80 chars 480 lines
# Blank Time 6.356 us 1.430 ms
# 20 chars 45 lines
# Polarity negative negative
#
mode "640x480-60"
# D: 25.175 MHz, H: 31.469 kHz, V: 59.94 Hz
geometry 640 480 640 480 32
timings 39722 48 16 33 10 96 2 endmode mode "480x640-60"
# D: 24.823 MHz, H: 39.780 kHz, V: 60.00 Hz
geometry 480 640 480 640 32 timings 39722 72 24 19 1 48 3 endmode
#
# 640x480, 75 Hz, Non-Interlaced (31.50 MHz dotclock)
#
# Horizontal Vertical
# Resolution 640 480
# Scan Frequency 37.500 kHz 75.00 Hz
# Sync Width 2.032 us 0.080 ms
# 8 chars 3 lines
# Front Porch 0.508 us 0.027 ms
# 2 chars 1 lines
# Back Porch 3.810 us 0.427 ms
# 15 chars 16 lines
# Active Time 20.317 us 12.800 ms
# 80 chars 480 lines
# Blank Time 6.349 us 0.533 ms
# 25 chars 20 lines
# Polarity negative negative
#
mode "640x480-75"
# D: 31.50 MHz, H: 37.500 kHz, V: 75.00 Hz
geometry 640 480 640 480 32 timings 31747 120 16 16 1 64 3 endmode
#
# 640x480, 85 Hz, Non-Interlaced (36.000 MHz dotclock)
#
# Horizontal Vertical
# Resolution 640 480
# Scan Frequency 43.269 kHz 85.00 Hz
# Sync Width 1.556 us 0.069 ms
# 7 chars 3 lines
# Front Porch 1.556 us 0.023 ms
# 7 chars 1 lines
# Back Porch 2.222 us 0.578 ms
# 10 chars 25 lines
# Active Time 17.778 us 11.093 ms
# 80 chars 480 lines
# Blank Time 5.333 us 0.670 ms
# 24 chars 29 lines
# Polarity negative negative
#
mode "640x480-85"
# D: 36.000 MHz, H: 43.269 kHz, V: 85.00 Hz
geometry 640 480 640 480 32 timings 27777 80 56 25 1 56 3 endmode
#
# 640x480, 100 Hz, Non-Interlaced (43.163 MHz dotclock)
#
# Horizontal Vertical
# Resolution 640 480
# Scan Frequency 50.900 kHz 100.00 Hz
# Sync Width 1.483 us 0.058 ms
# 8 chars 3 lines
# Front Porch 0.927 us 0.019 ms
# 5 chars 1 lines
# Back Porch 2.409 us 0.475 ms
# 13 chars 25 lines
# Active Time 14.827 us 9.430 ms
# 80 chars 480 lines
# Blank Time 4.819 us 0.570 ms
# 26 chars 29 lines
# Polarity positive positive
#
mode "640x480-100"
# D: 43.163 MHz, H: 50.900 kHz, V: 100.00 Hz
geometry 640 480 640 480 32 timings 23168 104 40 25 1 64 3 endmode
#
# 640x480, 120 Hz, Non-Interlaced (52.406 MHz dotclock)
#
# Horizontal Vertical
# Resolution 640 480
# Scan Frequency 61.800 kHz 120.00 Hz
# Sync Width 1.221 us 0.048 ms
# 8 chars 3 lines
# Front Porch 0.763 us 0.016 ms
# 5 chars 1 lines
# Back Porch 1.984 us 0.496 ms
# 13 chars 31 lines
# Active Time 12.212 us 7.767 ms
# 80 chars 480 lines
# Blank Time 3.969 us 0.566 ms
# 26 chars 35 lines
# Polarity positive positive
#
mode "640x480-120"
# D: 52.406 MHz, H: 61.800 kHz, V: 120.00 Hz
geometry 640 480 640 480 32 timings 19081 104 40 31 1 64 3 endmode
#
# 720x480, 60 Hz, Non-Interlaced (26.880 MHz dotclock)
#
# Horizontal Vertical
# Resolution 720 480
# Scan Frequency 30.000 kHz 60.241 Hz
# Sync Width 2.679 us 0.099 ms
# 9 chars 3 lines
# Front Porch 0.595 us 0.033 ms
# 2 chars 1 lines
# Back Porch 3.274 us 0.462 ms
# 11 chars 14 lines
# Active Time 26.786 us 16.000 ms
# 90 chars 480 lines
# Blank Time 6.548 us 0.600 ms
# 22 chars 18 lines
# Polarity positive positive
#
mode "720x480-60"
# D: 26.880 MHz, H: 30.000 kHz, V: 60.24 Hz
geometry 720 480 720 480 32 timings 37202 88 16 14 1 72 3 endmode
#
# 800x480, 60 Hz, Non-Interlaced (29.581 MHz dotclock)
#
# Horizontal Vertical
# Resolution 800 480
# Scan Frequency 29.892 kHz 60.00 Hz
# Sync Width 2.704 us 100.604 us
# 10 chars 3 lines
# Front Porch 0.541 us 33.535 us
# 2 chars 1 lines
# Back Porch 3.245 us 435.949 us
# 12 chars 13 lines
# Active Time 27.044 us 16.097 ms
# 100 chars 480 lines
# Blank Time 6.491 us 0.570 ms
# 24 chars 17 lines
# Polarity positive positive
#
mode "800x480-60"
# D: 29.500 MHz, H: 29.738 kHz, V: 60.00 Hz
geometry 800 480 800 480 32 timings 33805 96 24 10 3 72 7 endmode
#
# 720x576, 60 Hz, Non-Interlaced (32.668 MHz dotclock)
#
# Horizontal Vertical
# Resolution 720 576
# Scan Frequency 35.820 kHz 60.00 Hz
# Sync Width 2.204 us 0.083 ms
# 9 chars 3 lines
# Front Porch 0.735 us 0.027 ms
# 3 chars 1 lines
# Back Porch 2.939 us 0.459 ms
# 12 chars 17 lines
# Active Time 22.040 us 16.080 ms
# 90 chars 476 lines
# Blank Time 5.877 us 0.586 ms
# 24 chars 21 lines
# Polarity positive positive
#
mode "720x576-60"
# D: 32.668 MHz, H: 35.820 kHz, V: 60.00 Hz
geometry 720 576 720 576 32 timings 30611 96 24 17 1 72 3 endmode
#
# 800x600, 60 Hz, Non-Interlaced (40.00 MHz dotclock)
#
# Horizontal Vertical
# Resolution 800 600
# Scan Frequency 37.879 kHz 60.32 Hz
# Sync Width 3.200 us 0.106 ms
# 16 chars 4 lines
# Front Porch 1.000 us 0.026 ms
# 5 chars 1 lines
# Back Porch 2.200 us 0.607 ms
# 11 chars 23 lines
# Active Time 20.000 us 15.840 ms
# 100 chars 600 lines
# Blank Time 6.400 us 0.739 ms
# 32 chars 28 lines
# Polarity positive positive
#
mode "800x600-60"
# D: 40.00 MHz, H: 37.879 kHz, V: 60.32 Hz
geometry 800 600 800 600 32
timings 25000 88 40 23 1 128 4 hsync high vsync high endmode
#
# 800x600, 75 Hz, Non-Interlaced (49.50 MHz dotclock)
#
# Horizontal Vertical
# Resolution 800 600
# Scan Frequency 46.875 kHz 75.00 Hz
# Sync Width 1.616 us 0.064 ms
# 10 chars 3 lines
# Front Porch 0.323 us 0.021 ms
# 2 chars 1 lines
# Back Porch 3.232 us 0.448 ms
# 20 chars 21 lines
# Active Time 16.162 us 12.800 ms
# 100 chars 600 lines
# Blank Time 5.172 us 0.533 ms
# 32 chars 25 lines
# Polarity positive positive
#
mode "800x600-75"
# D: 49.50 MHz, H: 46.875 kHz, V: 75.00 Hz
geometry 800 600 800 600 32
timings 20203 160 16 21 1 80 3 hsync high vsync high endmode
#
# 800x600, 85 Hz, Non-Interlaced (56.25 MHz dotclock)
#
# Horizontal Vertical
# Resolution 800 600
# Scan Frequency 53.674 kHz 85.061 Hz
# Sync Width 1.138 us 0.056 ms
# 8 chars 3 lines
# Front Porch 0.569 us 0.019 ms
# 4 chars 1 lines
# Back Porch 2.702 us 0.503 ms
# 19 chars 27 lines
# Active Time 14.222 us 11.179 ms
# 100 chars 600 lines
# Blank Time 4.409 us 0.578 ms
# 31 chars 31 lines
# Polarity positive positive
#
mode "800x600-85"
# D: 56.25 MHz, H: 53.674 kHz, V: 85.061 Hz
geometry 800 600 800 600 32
timings 17777 152 32 27 1 64 3 hsync high vsync high endmode
#
# 800x600, 100 Hz, Non-Interlaced (67.50 MHz dotclock)
#
# Horizontal Vertical
# Resolution 800 600
# Scan Frequency 62.500 kHz 100.00 Hz
# Sync Width 0.948 us 0.064 ms
# 8 chars 4 lines
# Front Porch 0.000 us 0.112 ms
# 0 chars 7 lines
# Back Porch 3.200 us 0.224 ms
# 27 chars 14 lines
# Active Time 11.852 us 9.600 ms
# 100 chars 600 lines
# Blank Time 4.148 us 0.400 ms
# 35 chars 25 lines
# Polarity positive positive
#
mode "800x600-100"
# D: 67.50 MHz, H: 62.500 kHz, V: 100.00 Hz
geometry 800 600 800 600 32
timings 14667 216 0 14 7 64 4 hsync high vsync high endmode
#
# 800x600, 120 Hz, Non-Interlaced (83.950 MHz dotclock)
#
# Horizontal Vertical
# Resolution 800 600
# Scan Frequency 77.160 kHz 120.00 Hz
# Sync Width 1.048 us 0.039 ms
# 11 chars 3 lines
# Front Porch 0.667 us 0.013 ms
# 7 chars 1 lines
# Back Porch 1.715 us 0.507 ms
# 18 chars 39 lines
# Active Time 9.529 us 7.776 ms
# 100 chars 600 lines
# Blank Time 3.431 us 0.557 ms
# 36 chars 43 lines
# Polarity positive positive
#
mode "800x600-120"
# D: 83.950 MHz, H: 77.160 kHz, V: 120.00 Hz
geometry 800 600 800 600 32
timings 11912 144 56 39 1 88 3 hsync high vsync high endmode
#
# 848x480, 60 Hz, Non-Interlaced (31.490 MHz dotclock)
#
# Horizontal Vertical
# Resolution 848 480
# Scan Frequency 29.820 kHz 60.00 Hz
# Sync Width 2.795 us 0.099 ms
# 11 chars 3 lines
# Front Porch 0.508 us 0.033 ms
# 2 chars 1 lines
# Back Porch 3.303 us 0.429 ms
# 13 chars 13 lines
# Active Time 26.929 us 16.097 ms
# 106 chars 480 lines
# Blank Time 6.605 us 0.570 ms
# 26 chars 17 lines
# Polarity positive positive
#
mode "848x480-60"
# D: 31.500 MHz, H: 29.830 kHz, V: 60.00 Hz
geometry 848 480 848 480 32
timings 31746 104 24 12 3 80 5 hsync high vsync high endmode
#
# 856x480, 60 Hz, Non-Interlaced (31.728 MHz dotclock)
#
# Horizontal Vertical
# Resolution 856 480
# Scan Frequency 29.820 kHz 60.00 Hz
# Sync Width 2.774 us 0.099 ms
# 11 chars 3 lines
# Front Porch 0.504 us 0.033 ms
# 2 chars 1 lines
# Back Porch 3.728 us 0.429 ms
# 13 chars 13 lines
# Active Time 26.979 us 16.097 ms
# 107 chars 480 lines
# Blank Time 6.556 us 0.570 ms
# 26 chars 17 lines
# Polarity positive positive
#
mode "856x480-60"
# D: 31.728 MHz, H: 29.820 kHz, V: 60.00 Hz
geometry 856 480 856 480 32
timings 31518 104 16 13 1 88 3
hsync high vsync high endmode mode "960x600-60"
# D: 45.250 MHz, H: 37.212 kHz, V: 60.00 Hz
geometry 960 600 960 600 32 timings 22099 128 32 15 3 96 6 endmode
#
# 1000x600, 60 Hz, Non-Interlaced (48.068 MHz dotclock)
#
# Horizontal Vertical
# Resolution 1000 600
# Scan Frequency 37.320 kHz 60.00 Hz
# Sync Width 2.164 us 0.080 ms
# 13 chars 3 lines
# Front Porch 0.832 us 0.027 ms
# 5 chars 1 lines
# Back Porch 2.996 us 0.483 ms
# 18 chars 18 lines
# Active Time 20.804 us 16.077 ms
# 125 chars 600 lines
# Blank Time 5.991 us 0.589 ms
# 36 chars 22 lines
# Polarity negative positive
#
mode "1000x600-60"
# D: 48.068 MHz, H: 37.320 kHz, V: 60.00 Hz
geometry 1000 600 1000 600 32
timings 20834 144 40 18 1 104 3 endmode mode "1024x576-60"
# D: 46.996 MHz, H: 35.820 kHz, V: 60.00 Hz
geometry 1024 576 1024 576 32
timings 21278 144 40 17 1 104 3 endmode mode "1024x600-60"
# D: 48.964 MHz, H: 37.320 kHz, V: 60.00 Hz
geometry 1024 600 1024 600 32
timings 20461 144 40 18 1 104 3 endmode mode "1088x612-60"
# D: 52.952 MHz, H: 38.040 kHz, V: 60.00 Hz
geometry 1088 612 1088 612 32 timings 18877 152 48 16 3 104 5 endmode
#
# 1024x512, 60 Hz, Non-Interlaced (41.291 MHz dotclock)
#
# Horizontal Vertical
# Resolution 1024 512
# Scan Frequency 31.860 kHz 60.00 Hz
# Sync Width 2.519 us 0.094 ms
# 13 chars 3 lines
# Front Porch 0.775 us 0.031 ms
# 4 chars 1 lines
# Back Porch 3.294 us 0.465 ms
# 17 chars 15 lines
# Active Time 24.800 us 16.070 ms
# 128 chars 512 lines
# Blank Time 6.587 us 0.596 ms
# 34 chars 19 lines
# Polarity positive positive
#
mode "1024x512-60"
# D: 41.291 MHz, H: 31.860 kHz, V: 60.00 Hz
geometry 1024 512 1024 512 32
timings 24218 126 32 15 1 104 3 hsync high vsync high endmode
#
# 1024x600, 60 Hz, Non-Interlaced (48.875 MHz dotclock)
#
# Horizontal Vertical
# Resolution 1024 768
# Scan Frequency 37.252 kHz 60.00 Hz
# Sync Width 2.128 us 80.532us
# 13 chars 3 lines
# Front Porch 0.818 us 26.844 us
# 5 chars 1 lines
# Back Porch 2.946 us 483.192 us
# 18 chars 18 lines
# Active Time 20.951 us 16.697 ms
# 128 chars 622 lines
# Blank Time 5.893 us 0.591 ms
# 36 chars 22 lines
# Polarity negative positive
#
#mode "1024x600-60"
# # D: 48.875 MHz, H: 37.252 kHz, V: 60.00 Hz
# geometry 1024 600 1024 600 32
# timings 20460 144 40 18 1 104 3
# endmode
#
# 1024x768, 60 Hz, Non-Interlaced (65.00 MHz dotclock)
#
# Horizontal Vertical
# Resolution 1024 768
# Scan Frequency 48.363 kHz 60.00 Hz
# Sync Width 2.092 us 0.124 ms
# 17 chars 6 lines
# Front Porch 0.369 us 0.062 ms
# 3 chars 3 lines
# Back Porch 2.462 us 0.601 ms
# 20 chars 29 lines
# Active Time 15.754 us 15.880 ms
# 128 chars 768 lines
# Blank Time 4.923 us 0.786 ms
# 40 chars 38 lines
# Polarity negative negative
#
mode "1024x768-60"
# D: 65.00 MHz, H: 48.363 kHz, V: 60.00 Hz
geometry 1024 768 1024 768 32 timings 15385 160 24 29 3 136 6 endmode
#
# 1024x768, 75 Hz, Non-Interlaced (78.75 MHz dotclock)
#
# Horizontal Vertical
# Resolution 1024 768
# Scan Frequency 60.023 kHz 75.03 Hz
# Sync Width 1.219 us 0.050 ms
# 12 chars 3 lines
# Front Porch 0.203 us 0.017 ms
# 2 chars 1 lines
# Back Porch 2.235 us 0.466 ms
# 22 chars 28 lines
# Active Time 13.003 us 12.795 ms
# 128 chars 768 lines
# Blank Time 3.657 us 0.533 ms
# 36 chars 32 lines
# Polarity positive positive
#
mode "1024x768-75"
# D: 78.75 MHz, H: 60.023 kHz, V: 75.03 Hz
geometry 1024 768 1024 768 32
timings 12699 176 16 28 1 96 3 hsync high vsync high endmode
#
# 1024x768, 85 Hz, Non-Interlaced (94.50 MHz dotclock)
#
# Horizontal Vertical
# Resolution 1024 768
# Scan Frequency 68.677 kHz 85.00 Hz
# Sync Width 1.016 us 0.044 ms
# 12 chars 3 lines
# Front Porch 0.508 us 0.015 ms
# 6 chars 1 lines
# Back Porch 2.201 us 0.524 ms
# 26 chars 36 lines
# Active Time 10.836 us 11.183 ms
# 128 chars 768 lines
# Blank Time 3.725 us 0.582 ms
# 44 chars 40 lines
# Polarity positive positive
#
mode "1024x768-85"
# D: 94.50 MHz, H: 68.677 kHz, V: 85.00 Hz
geometry 1024 768 1024 768 32
timings 10582 208 48 36 1 96 3 hsync high vsync high endmode
#
# 1024x768, 100 Hz, Non-Interlaced (110.0 MHz dotclock)
#
# Horizontal Vertical
# Resolution 1024 768
# Scan Frequency 79.023 kHz 99.78 Hz
# Sync Width 0.800 us 0.101 ms
# 11 chars 8 lines
# Front Porch 0.000 us 0.000 ms
# 0 chars 0 lines
# Back Porch 2.545 us 0.202 ms
# 35 chars 16 lines
# Active Time 9.309 us 9.719 ms
# 128 chars 768 lines
# Blank Time 3.345 us 0.304 ms
# 46 chars 24 lines
# Polarity negative negative
#
mode "1024x768-100"
# D: 113.3 MHz, H: 79.023 kHz, V: 99.78 Hz
geometry 1024 768 1024 768 32
timings 8825 280 0 16 0 88 8 endmode mode "1152x720-60"
# D: 66.750 MHz, H: 44.859 kHz, V: 60.00 Hz
geometry 1152 720 1152 720 32 timings 14981 168 56 19 3 112 6 endmode
#
# 1152x864, 75 Hz, Non-Interlaced (110.0 MHz dotclock)
#
# Horizontal Vertical
# Resolution 1152 864
# Scan Frequency 75.137 kHz 74.99 Hz
# Sync Width 1.309 us 0.106 ms
# 18 chars 8 lines
# Front Porch 0.245 us 0.599 ms
# 3 chars 45 lines
# Back Porch 1.282 us 1.132 ms
# 18 chars 85 lines
# Active Time 10.473 us 11.499 ms
# 144 chars 864 lines
# Blank Time 2.836 us 1.837 ms
# 39 chars 138 lines
# Polarity positive positive
#
mode "1152x864-75"
# D: 110.0 MHz, H: 75.137 kHz, V: 74.99 Hz
geometry 1152 864 1152 864 32
timings 9259 144 24 85 45 144 8
hsync high vsync high endmode mode "1200x720-60"
# D: 70.184 MHz, H: 44.760 kHz, V: 60.00 Hz
geometry 1200 720 1200 720 32
timings 14253 184 28 22 1 128 3 endmode mode "1280x600-60"
# D: 61.503 MHz, H: 37.320 kHz, V: 60.00 Hz
geometry 1280 600 1280 600 32
timings 16260 184 28 18 1 128 3 endmode mode "1280x720-50"
# D: 60.466 MHz, H: 37.050 kHz, V: 50.00 Hz
geometry 1280 720 1280 720 32
timings 16538 176 48 17 1 128 3 endmode mode "1280x768-50"
# D: 65.178 MHz, H: 39.550 kHz, V: 50.00 Hz
geometry 1280 768 1280 768 32 timings 15342 184 28 19 1 128 3 endmode
#
# 1280x768, 60 Hz, Non-Interlaced (80.136 MHz dotclock)
#
# Horizontal Vertical
# Resolution 1280 768
# Scan Frequency 47.700 kHz 60.00 Hz
# Sync Width 1.697 us 0.063 ms
# 17 chars 3 lines
# Front Porch 0.799 us 0.021 ms
# 8 chars 1 lines
# Back Porch 2.496 us 0.483 ms
# 25 chars 23 lines
# Active Time 15.973 us 16.101 ms
# 160 chars 768 lines
# Blank Time 4.992 us 0.566 ms
# 50 chars 27 lines
# Polarity positive positive
#
mode "1280x768-60"
# D: 80.13 MHz, H: 47.700 kHz, V: 60.00 Hz
geometry 1280 768 1280 768 32
timings 12480 200 48 23 1 126 3 hsync high vsync high endmode
#
# 1280x800, 60 Hz, Non-Interlaced (83.375 MHz dotclock)
#
# Horizontal Vertical
# Resolution 1280 800
# Scan Frequency 49.628 kHz 60.00 Hz
# Sync Width 1.631 us 60.450 us
# 17 chars 3 lines
# Front Porch 0.768 us 20.15 us
# 8 chars 1 lines
# Back Porch 2.399 us 0.483 ms
# 25 chars 24 lines
# Active Time 15.352 us 16.120 ms
# 160 chars 800 lines
# Blank Time 4.798 us 0.564 ms
# 50 chars 28 lines
# Polarity negtive positive
#
mode "1280x800-60"
# D: 83.500 MHz, H: 49.702 kHz, V: 60.00 Hz
geometry 1280 800 1280 800 32 timings 11994 200 72 22 3 128 6 endmode
#
# 1280x960, 60 Hz, Non-Interlaced (108.00 MHz dotclock)
#
# Horizontal Vertical
# Resolution 1280 960
# Scan Frequency 60.000 kHz 60.00 Hz
# Sync Width 1.037 us 0.050 ms
# 14 chars 3 lines
# Front Porch 0.889 us 0.017 ms
# 12 chars 1 lines
# Back Porch 2.889 us 0.600 ms
# 39 chars 36 lines
# Active Time 11.852 us 16.000 ms
# 160 chars 960 lines
# Blank Time 4.815 us 0.667 ms
# 65 chars 40 lines
# Polarity positive positive
#
mode "1280x960-60"
# D: 108.00 MHz, H: 60.000 kHz, V: 60.00 Hz
geometry 1280 960 1280 960 32
timings 9259 312 96 36 1 112 3 hsync high vsync high endmode
#
# 1280x1024, 60 Hz, Non-Interlaced (108.00 MHz dotclock)
#
# Horizontal Vertical
# Resolution 1280 1024
# Scan Frequency 63.981 kHz 60.02 Hz
# Sync Width 1.037 us 0.047 ms
# 14 chars 3 lines
# Front Porch 0.444 us 0.015 ms
# 6 chars 1 lines
# Back Porch 2.297 us 0.594 ms
# 31 chars 38 lines
# Active Time 11.852 us 16.005 ms
# 160 chars 1024 lines
# Blank Time 3.778 us 0.656 ms
# 51 chars 42 lines
# Polarity positive positive
#
mode "1280x1024-60"
# D: 108.00 MHz, H: 63.981 kHz, V: 60.02 Hz
geometry 1280 1024 1280 1024 32
timings 9260 248 48 38 1 112 3 hsync high vsync high endmode
#
# 1280x1024, 75 Hz, Non-Interlaced (135.00 MHz dotclock)
#
# Horizontal Vertical
# Resolution 1280 1024
# Scan Frequency 79.976 kHz 75.02 Hz
# Sync Width 1.067 us 0.038 ms
# 18 chars 3 lines
# Front Porch 0.119 us 0.012 ms
# 2 chars 1 lines
# Back Porch 1.837 us 0.475 ms
# 31 chars 38 lines
# Active Time 9.481 us 12.804 ms
# 160 chars 1024 lines
# Blank Time 3.022 us 0.525 ms
# 51 chars 42 lines
# Polarity positive positive
#
mode "1280x1024-75"
# D: 135.00 MHz, H: 79.976 kHz, V: 75.02 Hz
geometry 1280 1024 1280 1024 32
timings 7408 248 16 38 1 144 3 hsync high vsync high endmode
#
# 1280x1024, 85 Hz, Non-Interlaced (157.50 MHz dotclock)
#
# Horizontal Vertical
# Resolution 1280 1024
# Scan Frequency 91.146 kHz 85.02 Hz
# Sync Width 1.016 us 0.033 ms
# 20 chars 3 lines
# Front Porch 0.406 us 0.011 ms
# 8 chars 1 lines
# Back Porch 1.422 us 0.483 ms
# 28 chars 44 lines
# Active Time 8.127 us 11.235 ms
# 160 chars 1024 lines
# Blank Time 2.844 us 0.527 ms
# 56 chars 48 lines
# Polarity positive positive
#
mode "1280x1024-85"
# D: 157.50 MHz, H: 91.146 kHz, V: 85.02 Hz
geometry 1280 1024 1280 1024 32
timings 6349 224 64 44 1 160 3
hsync high vsync high endmode mode "1440x900-60"
# D: 106.500 MHz, H: 55.935 kHz, V: 60.00 Hz
geometry 1440 900 1440 900 32
timings 9390 232 80 25 3 152 6
hsync high vsync high endmode mode "1440x900-75"
# D: 136.750 MHz, H: 70.635 kHz, V: 75.00 Hz
geometry 1440 900 1440 900 32
timings 7315 248 96 33 3 152 6 hsync high vsync high endmode
#
# 1440x1050, 60 Hz, Non-Interlaced (125.10 MHz dotclock)
#
# Horizontal Vertical
# Resolution 1440 1050
# Scan Frequency 65.220 kHz 60.00 Hz
# Sync Width 1.204 us 0.046 ms
# 19 chars 3 lines
# Front Porch 0.760 us 0.015 ms
# 12 chars 1 lines
# Back Porch 1.964 us 0.495 ms
# 31 chars 33 lines
# Active Time 11.405 us 16.099 ms
# 180 chars 1050 lines
# Blank Time 3.928 us 0.567 ms
# 62 chars 37 lines
# Polarity positive positive
#
mode "1440x1050-60"
# D: 125.10 MHz, H: 65.220 kHz, V: 60.00 Hz
geometry 1440 1050 1440 1050 32
timings 7993 248 96 33 1 152 3
hsync high vsync high endmode mode "1600x900-60"
# D: 118.250 MHz, H: 55.990 kHz, V: 60.00 Hz
geometry 1600 900 1600 900 32
timings 8415 256 88 26 3 168 5 endmode mode "1600x1024-60"
# D: 136.358 MHz, H: 63.600 kHz, V: 60.00 Hz
geometry 1600 1024 1600 1024 32 timings 7315 272 104 32 1 168 3 endmode
#
# 1600x1200, 60 Hz, Non-Interlaced (156.00 MHz dotclock)
#
# Horizontal Vertical
# Resolution 1600 1200
# Scan Frequency 76.200 kHz 60.00 Hz
# Sync Width 1.026 us 0.105 ms
# 20 chars 8 lines
# Front Porch 0.205 us 0.131 ms
# 4 chars 10 lines
# Back Porch 1.636 us 0.682 ms
# 32 chars 52 lines
# Active Time 10.256 us 15.748 ms
# 200 chars 1200 lines
# Blank Time 2.872 us 0.866 ms
# 56 chars 66 lines
# Polarity negative negative
#
mode "1600x1200-60"
# D: 156.00 MHz, H: 76.200 kHz, V: 60.00 Hz
geometry 1600 1200 1600 1200 32 timings 6172 256 32 52 10 160 8 endmode
#
# 1600x1200, 75 Hz, Non-Interlaced (202.50 MHz dotclock)
#
# Horizontal Vertical
# Resolution 1600 1200
# Scan Frequency 93.750 kHz 75.00 Hz
# Sync Width 0.948 us 0.032 ms
# 24 chars 3 lines
# Front Porch 0.316 us 0.011 ms
# 8 chars 1 lines
# Back Porch 1.501 us 0.491 ms
# 38 chars 46 lines
# Active Time 7.901 us 12.800 ms
# 200 chars 1200 lines
# Blank Time 2.765 us 0.533 ms
# 70 chars 50 lines
# Polarity positive positive
#
mode "1600x1200-75"
# D: 202.50 MHz, H: 93.750 kHz, V: 75.00 Hz
geometry 1600 1200 1600 1200 32
timings 4938 304 64 46 1 192 3
hsync high vsync high endmode mode "1680x1050-60"
# D: 146.250 MHz, H: 65.290 kHz, V: 59.954 Hz
geometry 1680 1050 1680 1050 32
timings 6814 280 104 30 3 176 6
hsync high vsync high endmode mode "1680x1050-75"
# D: 187.000 MHz, H: 82.306 kHz, V: 74.892 Hz
geometry 1680 1050 1680 1050 32
timings 5348 296 120 40 3 176 6
hsync high vsync high endmode mode "1792x1344-60"
# D: 202.975 MHz, H: 83.460 kHz, V: 60.00 Hz
geometry 1792 1344 1792 1344 32
timings 4902 320 128 43 1 192 3
hsync high vsync high endmode mode "1856x1392-60"
# D: 218.571 MHz, H: 86.460 kHz, V: 60.00 Hz
geometry 1856 1392 1856 1392 32
timings 4577 336 136 45 1 200 3
hsync high vsync high endmode mode "1920x1200-60"
# D: 193.250 MHz, H: 74.556 kHz, V: 60.00 Hz
geometry 1920 1200 1920 1200 32
timings 5173 336 136 36 3 200 6
hsync high vsync high endmode mode "1920x1440-60"
# D: 234.000 MHz, H:90.000 kHz, V: 60.00 Hz
geometry 1920 1440 1920 1440 32
timings 4274 344 128 56 1 208 3
hsync high vsync high endmode mode "1920x1440-75"
# D: 297.000 MHz, H:112.500 kHz, V: 75.00 Hz
geometry 1920 1440 1920 1440 32
timings 3367 352 144 56 1 224 3
hsync high vsync high endmode mode "2048x1536-60"
# D: 267.250 MHz, H: 95.446 kHz, V: 60.00 Hz
geometry 2048 1536 2048 1536 32
timings 3742 376 152 49 3 224 4 hsync high vsync high endmode
#
# 1280x720, 60 Hz, Non-Interlaced (74.481 MHz dotclock)
#
# Horizontal Vertical
# Resolution 1280 720
# Scan Frequency 44.760 kHz 60.00 Hz
# Sync Width 1.826 us 67.024 ms
# 17 chars 3 lines
# Front Porch 0.752 us 22.341 ms
# 7 chars 1 lines
# Back Porch 2.578 us 491.510 ms
# 24 chars 22 lines
# Active Time 17.186 us 16.086 ms
# 160 chars 720 lines
# Blank Time 5.156 us 0.581 ms
# 48 chars 26 lines
# Polarity negative negative
#
mode "1280x720-60"
# D: 74.481 MHz, H: 44.760 kHz, V: 60.00 Hz
geometry 1280 720 1280 720 32 timings 13426 192 64 22 1 136 3 endmode
#
# 1920x1080, 60 Hz, Non-Interlaced (172.798 MHz dotclock)
#
# Horizontal Vertical
# Resolution 1920 1080
# Scan Frequency 67.080 kHz 60.00 Hz
# Sync Width 1.204 us 44.723 ms
# 26 chars 3 lines
# Front Porch 0.694 us 14.908 ms
# 15 chars 1 lines
# Back Porch 1.898 us 506.857 ms
# 41 chars 34 lines
# Active Time 11.111 us 16.100 ms
# 240 chars 1080 lines
# Blank Time 3.796 us 0.566 ms
# 82 chars 38 lines
# Polarity negative negative
#
mode "1920x1080-60"
# D: 74.481 MHz, H: 67.080 kHz, V: 60.00 Hz
geometry 1920 1080 1920 1080 32 timings 5787 328 120 34 1 208 3 endmode
#
# 1400x1050, 60 Hz, Non-Interlaced (122.61 MHz dotclock)
#
# Horizontal Vertical
# Resolution 1400 1050
# Scan Frequency 65.218 kHz 59.99 Hz
# Sync Width 1.037 us 0.047 ms
# 19 chars 3 lines
# Front Porch 0.444 us 0.015 ms
# 11 chars 1 lines
# Back Porch 1.185 us 0.188 ms
# 30 chars 33 lines
# Active Time 12.963 us 16.411 ms
# 175 chars 1050 lines
# Blank Time 2.667 us 0.250 ms
# 60 chars 37 lines
# Polarity negative positive
#
mode "1400x1050-60"
# D: 122.750 MHz, H: 65.317 kHz, V: 59.99 Hz
geometry 1400 1050 1408 1050 32
timings 8214 232 88 32 3 144 4 endmode mode "1400x1050-75"
# D: 156.000 MHz, H: 82.278 kHz, V: 74.867 Hz
geometry 1400 1050 1408 1050 32 timings 6410 248 104 42 3 144 4 endmode
#
# 1366x768, 60 Hz, Non-Interlaced (85.86 MHz dotclock)
#
# Horizontal Vertical
# Resolution 1366 768
# Scan Frequency 47.700 kHz 60.00 Hz
# Sync Width 1.677 us 0.063 ms
# 18 chars 3 lines
# Front Porch 0.839 us 0.021 ms
# 9 chars 1 lines
# Back Porch 2.516 us 0.482 ms
# 27 chars 23 lines
# Active Time 15.933 us 16.101 ms
# 171 chars 768 lines
# Blank Time 5.031 us 0.566 ms
# 54 chars 27 lines
# Polarity negative positive
#
mode "1360x768-60"
# D: 84.750 MHz, H: 47.720 kHz, V: 60.00 Hz
geometry 1360 768 1360 768 32
timings 11799 208 72 22 3 136 5 endmode mode "1366x768-60"
# D: 85.86 MHz, H: 47.700 kHz, V: 60.00 Hz
geometry 1366 768 1366 768 32
timings 11647 216 72 23 1 144 3 endmode mode "1366x768-50"
# D: 69,924 MHz, H: 39.550 kHz, V: 50.00 Hz
geometry 1366 768 1366 768 32 timings 14301 200 56 19 1 144 3 endmode

214
Documentation/fb/viafb.txt Normal file
View File

@ -0,0 +1,214 @@
VIA Integration Graphic Chip Console Framebuffer Driver
[Platform]
-----------------------
The console framebuffer driver is for graphics chips of
VIA UniChrome Family(CLE266, PM800 / CN400 / CN300,
P4M800CE / P4M800Pro / CN700 / VN800,
CX700 / VX700, K8M890, P4M890,
CN896 / P4M900, VX800)
[Driver features]
------------------------
Device: CRT, LCD, DVI
Support viafb_mode:
CRT:
640x480(60, 75, 85, 100, 120 Hz), 720x480(60 Hz),
720x576(60 Hz), 800x600(60, 75, 85, 100, 120 Hz),
848x480(60 Hz), 856x480(60 Hz), 1024x512(60 Hz),
1024x768(60, 75, 85, 100 Hz), 1152x864(75 Hz),
1280x768(60 Hz), 1280x960(60 Hz), 1280x1024(60, 75, 85 Hz),
1440x1050(60 Hz), 1600x1200(60, 75 Hz), 1280x720(60 Hz),
1920x1080(60 Hz), 1400x1050(60 Hz), 800x480(60 Hz)
color depth: 8 bpp, 16 bpp, 32 bpp supports.
Support 2D hardware accelerator.
[Using the viafb module]
-- -- --------------------
Start viafb with default settings:
#modprobe viafb
Start viafb with with user options:
#modprobe viafb viafb_mode=800x600 viafb_bpp=16 viafb_refresh=60
viafb_active_dev=CRT+DVI viafb_dvi_port=DVP1
viafb_mode1=1024x768 viafb_bpp=16 viafb_refresh1=60
viafb_SAMM_ON=1
viafb_mode:
640x480 (default)
720x480
800x600
1024x768
......
viafb_bpp:
8, 16, 32 (default:32)
viafb_refresh:
60, 75, 85, 100, 120 (default:60)
viafb_lcd_dsp_method:
0 : expansion (default)
1 : centering
viafb_lcd_mode:
0 : LCD panel with LSB data format input (default)
1 : LCD panel with MSB data format input
viafb_lcd_panel_id:
0 : Resolution: 640x480, Channel: single, Dithering: Enable
1 : Resolution: 800x600, Channel: single, Dithering: Enable
2 : Resolution: 1024x768, Channel: single, Dithering: Enable (default)
3 : Resolution: 1280x768, Channel: single, Dithering: Enable
4 : Resolution: 1280x1024, Channel: dual, Dithering: Enable
5 : Resolution: 1400x1050, Channel: dual, Dithering: Enable
6 : Resolution: 1600x1200, Channel: dual, Dithering: Enable
8 : Resolution: 800x480, Channel: single, Dithering: Enable
9 : Resolution: 1024x768, Channel: dual, Dithering: Enable
10: Resolution: 1024x768, Channel: single, Dithering: Disable
11: Resolution: 1024x768, Channel: dual, Dithering: Disable
12: Resolution: 1280x768, Channel: single, Dithering: Disable
13: Resolution: 1280x1024, Channel: dual, Dithering: Disable
14: Resolution: 1400x1050, Channel: dual, Dithering: Disable
15: Resolution: 1600x1200, Channel: dual, Dithering: Disable
16: Resolution: 1366x768, Channel: single, Dithering: Disable
17: Resolution: 1024x600, Channel: single, Dithering: Enable
18: Resolution: 1280x768, Channel: dual, Dithering: Enable
19: Resolution: 1280x800, Channel: single, Dithering: Enable
viafb_accel:
0 : No 2D Hardware Acceleration
1 : 2D Hardware Acceleration (default)
viafb_SAMM_ON:
0 : viafb_SAMM_ON disable (default)
1 : viafb_SAMM_ON enable
viafb_mode1: (secondary display device)
640x480 (default)
720x480
800x600
1024x768
... ...
viafb_bpp1: (secondary display device)
8, 16, 32 (default:32)
viafb_refresh1: (secondary display device)
60, 75, 85, 100, 120 (default:60)
viafb_active_dev:
This option is used to specify active devices.(CRT, DVI, CRT+LCD...)
DVI stands for DVI or HDMI, E.g., If you want to enable HDMI,
set viafb_active_dev=DVI. In SAMM case, the previous of
viafb_active_dev is primary device, and the following is
secondary device.
For example:
To enable one device, such as DVI only, we can use:
modprobe viafb viafb_active_dev=DVI
To enable two devices, such as CRT+DVI:
modprobe viafb viafb_active_dev=CRT+DVI;
For DuoView case, we can use:
modprobe viafb viafb_active_dev=CRT+DVI
OR
modprobe viafb viafb_active_dev=DVI+CRT...
For SAMM case:
If CRT is primary and DVI is secondary, we should use:
modprobe viafb viafb_active_dev=CRT+DVI viafb_SAMM_ON=1...
If DVI is primary and CRT is secondary, we should use:
modprobe viafb viafb_active_dev=DVI+CRT viafb_SAMM_ON=1...
viafb_display_hardware_layout:
This option is used to specify display hardware layout for CX700 chip.
1 : LCD only
2 : DVI only
3 : LCD+DVI (default)
4 : LCD1+LCD2 (internal + internal)
16: LCD1+ExternalLCD2 (internal + external)
viafb_second_size:
This option is used to set second device memory size(MB) in SAMM case.
The minimal size is 16.
viafb_platform_epia_dvi:
This option is used to enable DVI on EPIA - M
0 : No DVI on EPIA - M (default)
1 : DVI on EPIA - M
viafb_bus_width:
When using 24 - Bit Bus Width Digital Interface,
this option should be set.
12: 12-Bit LVDS or 12-Bit TMDS (default)
24: 24-Bit LVDS or 24-Bit TMDS
viafb_device_lcd_dualedge:
When using Dual Edge Panel, this option should be set.
0 : No Dual Edge Panel (default)
1 : Dual Edge Panel
viafb_video_dev:
This option is used to specify video output devices(CRT, DVI, LCD) for
duoview case.
For example:
To output video on DVI, we should use:
modprobe viafb viafb_video_dev=DVI...
viafb_lcd_port:
This option is used to specify LCD output port,
available values are "DVP0" "DVP1" "DFP_HIGHLOW" "DFP_HIGH" "DFP_LOW".
for external LCD + external DVI on CX700(External LCD is on DVP0),
we should use:
modprobe viafb viafb_lcd_port=DVP0...
Notes:
1. CRT may not display properly for DuoView CRT & DVI display at
the "640x480" PAL mode with DVI overscan enabled.
2. SAMM stands for single adapter multi monitors. It is different from
multi-head since SAMM support multi monitor at driver layers, thus fbcon
layer doesn't even know about it; SAMM's second screen doesn't have a
device node file, thus a user mode application can't access it directly.
When SAMM is enabled, viafb_mode and viafb_mode1, viafb_bpp and
viafb_bpp1, viafb_refresh and viafb_refresh1 can be different.
3. When console is depending on viafbinfo1, dynamically change resolution
and bpp, need to call VIAFB specified ioctl interface VIAFB_SET_DEVICE
instead of calling common ioctl function FBIOPUT_VSCREENINFO since
viafb doesn't support multi-head well, or it will cause screen crush.
4. VX800 2D accelerator hasn't been supported in this driver yet. When
using driver on VX800, the driver will disable the acceleration
function as default.
[Configure viafb with "fbset" tool]
-----------------------------------
"fbset" is an inbox utility of Linux.
1. Inquire current viafb information, type,
# fbset -i
2. Set various resolutions and viafb_refresh rates,
# fbset <resolution-vertical_sync>
example,
# fbset "1024x768-75"
or
# fbset -g 1024 768 1024 768 32
Check the file "/etc/fb.modes" to find display modes available.
3. Set the color depth,
# fbset -depth <value>
example,
# fbset -depth 16
[Bootup with viafb]:
--------------------
Add the following line to your grub.conf:
append = "video=viafb:viafb_mode=1024x768,viafb_bpp=32,viafb_refresh=85"

39
Documentation/feature-removal-schedule.txt
View File

@ -6,6 +6,24 @@ be removed from this file.
---------------------------
What: old static regulatory information and ieee80211_regdom module parameter
When: 2.6.29
Why: The old regulatory infrastructure has been replaced with a new one
which does not require statically defined regulatory domains. We do
not want to keep static regulatory domains in the kernel due to the
the dynamic nature of regulatory law and localization. We kept around
the old static definitions for the regulatory domains of:
* US
* JP
* EU
and used by default the US when CONFIG_WIRELESS_OLD_REGULATORY was
set. We also kept around the ieee80211_regdom module parameter in case
some applications were relying on it. Changing regulatory domains
can now be done instead by using nl80211, as is done with iw.
Who: Luis R. Rodriguez <lrodriguez@atheros.com>
---------------------------
What: dev->power.power_state
When: July 2007
Why: Broken design for runtime control over driver power states, confusing
@ -232,6 +250,9 @@ What (Why):
- xt_mark match revision 0
(superseded by xt_mark match revision 1)
- xt_recent: the old ipt_recent proc dir
(superseded by /proc/net/xt_recent)
When: January 2009 or Linux 2.7.0, whichever comes first
Why: Superseded by newer revisions or modules
Who: Jan Engelhardt <jengelh@computergmbh.de>
@ -266,11 +287,19 @@ Who: Glauber Costa <gcosta@redhat.com>
---------------------------
What: old style serial driver for ColdFire (CONFIG_SERIAL_COLDFIRE)
When: 2.6.28
Why: This driver still uses the old interface and has been replaced
by CONFIG_SERIAL_MCF.
Who: Sebastian Siewior <sebastian@breakpoint.cc>
What: remove HID compat support
When: 2.6.29
Why: needed only as a temporary solution until distros fix themselves up
Who: Jiri Slaby <jirislaby@gmail.com>
---------------------------
What: print_fn_descriptor_symbol()
When: October 2009
Why: The %pF vsprintf format provides the same functionality in a
simpler way. print_fn_descriptor_symbol() is deprecated but
still present to give out-of-tree modules time to change.
Who: Bjorn Helgaas <bjorn.helgaas@hp.com>
---------------------------

393
Documentation/filesystems/autofs4-mount-control.txt Normal file
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@ -0,0 +1,393 @@
Miscellaneous Device control operations for the autofs4 kernel module
====================================================================
The problem
===========
There is a problem with active restarts in autofs (that is to say
restarting autofs when there are busy mounts).
During normal operation autofs uses a file descriptor opened on the
directory that is being managed in order to be able to issue control
operations. Using a file descriptor gives ioctl operations access to
autofs specific information stored in the super block. The operations
are things such as setting an autofs mount catatonic, setting the
expire timeout and requesting expire checks. As is explained below,
certain types of autofs triggered mounts can end up covering an autofs
mount itself which prevents us being able to use open(2) to obtain a
file descriptor for these operations if we don't already have one open.
Currently autofs uses "umount -l" (lazy umount) to clear active mounts
at restart. While using lazy umount works for most cases, anything that
needs to walk back up the mount tree to construct a path, such as
getcwd(2) and the proc file system /proc/<pid>/cwd, no longer works
because the point from which the path is constructed has been detached
from the mount tree.
The actual problem with autofs is that it can't reconnect to existing
mounts. Immediately one thinks of just adding the ability to remount
autofs file systems would solve it, but alas, that can't work. This is
because autofs direct mounts and the implementation of "on demand mount
and expire" of nested mount trees have the file system mounted directly
on top of the mount trigger directory dentry.
For example, there are two types of automount maps, direct (in the kernel
module source you will see a third type called an offset, which is just
a direct mount in disguise) and indirect.
Here is a master map with direct and indirect map entries:
/- /etc/auto.direct
/test /etc/auto.indirect
and the corresponding map files:
/etc/auto.direct:
/automount/dparse/g6 budgie:/autofs/export1
/automount/dparse/g1 shark:/autofs/export1
and so on.
/etc/auto.indirect:
g1 shark:/autofs/export1
g6 budgie:/autofs/export1
and so on.
For the above indirect map an autofs file system is mounted on /test and
mounts are triggered for each sub-directory key by the inode lookup
operation. So we see a mount of shark:/autofs/export1 on /test/g1, for
example.
The way that direct mounts are handled is by making an autofs mount on
each full path, such as /automount/dparse/g1, and using it as a mount
trigger. So when we walk on the path we mount shark:/autofs/export1 "on
top of this mount point". Since these are always directories we can
use the follow_link inode operation to trigger the mount.
But, each entry in direct and indirect maps can have offsets (making
them multi-mount map entries).
For example, an indirect mount map entry could also be:
g1 \
/ shark:/autofs/export5/testing/test \
/s1 shark:/autofs/export/testing/test/s1 \
/s2 shark:/autofs/export5/testing/test/s2 \
/s1/ss1 shark:/autofs/export1 \
/s2/ss2 shark:/autofs/export2
and a similarly a direct mount map entry could also be:
/automount/dparse/g1 \
/ shark:/autofs/export5/testing/test \
/s1 shark:/autofs/export/testing/test/s1 \
/s2 shark:/autofs/export5/testing/test/s2 \
/s1/ss1 shark:/autofs/export2 \
/s2/ss2 shark:/autofs/export2
One of the issues with version 4 of autofs was that, when mounting an
entry with a large number of offsets, possibly with nesting, we needed
to mount and umount all of the offsets as a single unit. Not really a
problem, except for people with a large number of offsets in map entries.
This mechanism is used for the well known "hosts" map and we have seen
cases (in 2.4) where the available number of mounts are exhausted or
where the number of privileged ports available is exhausted.
In version 5 we mount only as we go down the tree of offsets and
similarly for expiring them which resolves the above problem. There is
somewhat more detail to the implementation but it isn't needed for the
sake of the problem explanation. The one important detail is that these
offsets are implemented using the same mechanism as the direct mounts
above and so the mount points can be covered by a mount.
The current autofs implementation uses an ioctl file descriptor opened
on the mount point for control operations. The references held by the
descriptor are accounted for in checks made to determine if a mount is
in use and is also used to access autofs file system information held
in the mount super block. So the use of a file handle needs to be
retained.
The Solution
============
To be able to restart autofs leaving existing direct, indirect and
offset mounts in place we need to be able to obtain a file handle
for these potentially covered autofs mount points. Rather than just
implement an isolated operation it was decided to re-implement the
existing ioctl interface and add new operations to provide this
functionality.
In addition, to be able to reconstruct a mount tree that has busy mounts,
the uid and gid of the last user that triggered the mount needs to be
available because these can be used as macro substitution variables in
autofs maps. They are recorded at mount request time and an operation
has been added to retrieve them.
Since we're re-implementing the control interface, a couple of other
problems with the existing interface have been addressed. First, when
a mount or expire operation completes a status is returned to the
kernel by either a "send ready" or a "send fail" operation. The
"send fail" operation of the ioctl interface could only ever send
ENOENT so the re-implementation allows user space to send an actual
status. Another expensive operation in user space, for those using
very large maps, is discovering if a mount is present. Usually this
involves scanning /proc/mounts and since it needs to be done quite
often it can introduce significant overhead when there are many entries
in the mount table. An operation to lookup the mount status of a mount
point dentry (covered or not) has also been added.
Current kernel development policy recommends avoiding the use of the
ioctl mechanism in favor of systems such as Netlink. An implementation
using this system was attempted to evaluate its suitability and it was
found to be inadequate, in this case. The Generic Netlink system was
used for this as raw Netlink would lead to a significant increase in
complexity. There's no question that the Generic Netlink system is an
elegant solution for common case ioctl functions but it's not a complete
replacement probably because it's primary purpose in life is to be a
message bus implementation rather than specifically an ioctl replacement.
While it would be possible to work around this there is one concern
that lead to the decision to not use it. This is that the autofs
expire in the daemon has become far to complex because umount
candidates are enumerated, almost for no other reason than to "count"
the number of times to call the expire ioctl. This involves scanning
the mount table which has proved to be a big overhead for users with
large maps. The best way to improve this is try and get back to the
way the expire was done long ago. That is, when an expire request is
issued for a mount (file handle) we should continually call back to
the daemon until we can't umount any more mounts, then return the
appropriate status to the daemon. At the moment we just expire one
mount at a time. A Generic Netlink implementation would exclude this
possibility for future development due to the requirements of the
message bus architecture.
autofs4 Miscellaneous Device mount control interface
====================================================
The control interface is opening a device node, typically /dev/autofs.
All the ioctls use a common structure to pass the needed parameter
information and return operation results:
struct autofs_dev_ioctl {
__u32 ver_major;
__u32 ver_minor;
__u32 size; /* total size of data passed in
* including this struct */
__s32 ioctlfd; /* automount command fd */
__u32 arg1; /* Command parameters */
__u32 arg2;
char path[0];
};
The ioctlfd field is a mount point file descriptor of an autofs mount
point. It is returned by the open call and is used by all calls except
the check for whether a given path is a mount point, where it may
optionally be used to check a specific mount corresponding to a given
mount point file descriptor, and when requesting the uid and gid of the
last successful mount on a directory within the autofs file system.
The fields arg1 and arg2 are used to communicate parameters and results of
calls made as described below.
The path field is used to pass a path where it is needed and the size field
is used account for the increased structure length when translating the
structure sent from user space.
This structure can be initialized before setting specific fields by using
the void function call init_autofs_dev_ioctl(struct autofs_dev_ioctl *).
All of the ioctls perform a copy of this structure from user space to
kernel space and return -EINVAL if the size parameter is smaller than
the structure size itself, -ENOMEM if the kernel memory allocation fails
or -EFAULT if the copy itself fails. Other checks include a version check
of the compiled in user space version against the module version and a
mismatch results in a -EINVAL return. If the size field is greater than
the structure size then a path is assumed to be present and is checked to
ensure it begins with a "/" and is NULL terminated, otherwise -EINVAL is
returned. Following these checks, for all ioctl commands except
AUTOFS_DEV_IOCTL_VERSION_CMD, AUTOFS_DEV_IOCTL_OPENMOUNT_CMD and
AUTOFS_DEV_IOCTL_CLOSEMOUNT_CMD the ioctlfd is validated and if it is
not a valid descriptor or doesn't correspond to an autofs mount point
an error of -EBADF, -ENOTTY or -EINVAL (not an autofs descriptor) is
returned.
The ioctls
==========
An example of an implementation which uses this interface can be seen
in autofs version 5.0.4 and later in file lib/dev-ioctl-lib.c of the
distribution tar available for download from kernel.org in directory
/pub/linux/daemons/autofs/v5.
The device node ioctl operations implemented by this interface are:
AUTOFS_DEV_IOCTL_VERSION
------------------------
Get the major and minor version of the autofs4 device ioctl kernel module
implementation. It requires an initialized struct autofs_dev_ioctl as an
input parameter and sets the version information in the passed in structure.
It returns 0 on success or the error -EINVAL if a version mismatch is
detected.
AUTOFS_DEV_IOCTL_PROTOVER_CMD and AUTOFS_DEV_IOCTL_PROTOSUBVER_CMD
------------------------------------------------------------------
Get the major and minor version of the autofs4 protocol version understood
by loaded module. This call requires an initialized struct autofs_dev_ioctl
with the ioctlfd field set to a valid autofs mount point descriptor
and sets the requested version number in structure field arg1. These
commands return 0 on success or one of the negative error codes if
validation fails.
AUTOFS_DEV_IOCTL_OPENMOUNT and AUTOFS_DEV_IOCTL_CLOSEMOUNT
----------------------------------------------------------
Obtain and release a file descriptor for an autofs managed mount point
path. The open call requires an initialized struct autofs_dev_ioctl with
the the path field set and the size field adjusted appropriately as well
as the arg1 field set to the device number of the autofs mount. The
device number can be obtained from the mount options shown in
/proc/mounts. The close call requires an initialized struct
autofs_dev_ioct with the ioctlfd field set to the descriptor obtained
from the open call. The release of the file descriptor can also be done
with close(2) so any open descriptors will also be closed at process exit.
The close call is included in the implemented operations largely for
completeness and to provide for a consistent user space implementation.
AUTOFS_DEV_IOCTL_READY_CMD and AUTOFS_DEV_IOCTL_FAIL_CMD
--------------------------------------------------------
Return mount and expire result status from user space to the kernel.
Both of these calls require an initialized struct autofs_dev_ioctl
with the ioctlfd field set to the descriptor obtained from the open
call and the arg1 field set to the wait queue token number, received
by user space in the foregoing mount or expire request. The arg2 field
is set to the status to be returned. For the ready call this is always
0 and for the fail call it is set to the errno of the operation.
AUTOFS_DEV_IOCTL_SETPIPEFD_CMD
------------------------------
Set the pipe file descriptor used for kernel communication to the daemon.
Normally this is set at mount time using an option but when reconnecting
to a existing mount we need to use this to tell the autofs mount about
the new kernel pipe descriptor. In order to protect mounts against
incorrectly setting the pipe descriptor we also require that the autofs
mount be catatonic (see next call).
The call requires an initialized struct autofs_dev_ioctl with the
ioctlfd field set to the descriptor obtained from the open call and
the arg1 field set to descriptor of the pipe. On success the call
also sets the process group id used to identify the controlling process
(eg. the owning automount(8) daemon) to the process group of the caller.
AUTOFS_DEV_IOCTL_CATATONIC_CMD
------------------------------
Make the autofs mount point catatonic. The autofs mount will no longer
issue mount requests, the kernel communication pipe descriptor is released
and any remaining waits in the queue released.
The call requires an initialized struct autofs_dev_ioctl with the
ioctlfd field set to the descriptor obtained from the open call.
AUTOFS_DEV_IOCTL_TIMEOUT_CMD
----------------------------
Set the expire timeout for mounts withing an autofs mount point.
The call requires an initialized struct autofs_dev_ioctl with the
ioctlfd field set to the descriptor obtained from the open call.
AUTOFS_DEV_IOCTL_REQUESTER_CMD
------------------------------
Return the uid and gid of the last process to successfully trigger a the
mount on the given path dentry.
The call requires an initialized struct autofs_dev_ioctl with the path
field set to the mount point in question and the size field adjusted
appropriately as well as the arg1 field set to the device number of the
containing autofs mount. Upon return the struct field arg1 contains the
uid and arg2 the gid.
When reconstructing an autofs mount tree with active mounts we need to
re-connect to mounts that may have used the original process uid and
gid (or string variations of them) for mount lookups within the map entry.
This call provides the ability to obtain this uid and gid so they may be
used by user space for the mount map lookups.
AUTOFS_DEV_IOCTL_EXPIRE_CMD
---------------------------
Issue an expire request to the kernel for an autofs mount. Typically
this ioctl is called until no further expire candidates are found.
The call requires an initialized struct autofs_dev_ioctl with the
ioctlfd field set to the descriptor obtained from the open call. In
addition an immediate expire, independent of the mount timeout, can be
requested by setting the arg1 field to 1. If no expire candidates can
be found the ioctl returns -1 with errno set to EAGAIN.
This call causes the kernel module to check the mount corresponding
to the given ioctlfd for mounts that can be expired, issues an expire
request back to the daemon and waits for completion.
AUTOFS_DEV_IOCTL_ASKUMOUNT_CMD
------------------------------
Checks if an autofs mount point is in use.
The call requires an initialized struct autofs_dev_ioctl with the
ioctlfd field set to the descriptor obtained from the open call and
it returns the result in the arg1 field, 1 for busy and 0 otherwise.
AUTOFS_DEV_IOCTL_ISMOUNTPOINT_CMD
---------------------------------
Check if the given path is a mountpoint.
The call requires an initialized struct autofs_dev_ioctl. There are two
possible variations. Both use the path field set to the path of the mount
point to check and the size field adjusted appropriately. One uses the
ioctlfd field to identify a specific mount point to check while the other
variation uses the path and optionaly arg1 set to an autofs mount type.
The call returns 1 if this is a mount point and sets arg1 to the device
number of the mount and field arg2 to the relevant super block magic
number (described below) or 0 if it isn't a mountpoint. In both cases
the the device number (as returned by new_encode_dev()) is returned
in field arg1.
If supplied with a file descriptor we're looking for a specific mount,
not necessarily at the top of the mounted stack. In this case the path
the descriptor corresponds to is considered a mountpoint if it is itself
a mountpoint or contains a mount, such as a multi-mount without a root
mount. In this case we return 1 if the descriptor corresponds to a mount
point and and also returns the super magic of the covering mount if there
is one or 0 if it isn't a mountpoint.
If a path is supplied (and the ioctlfd field is set to -1) then the path
is looked up and is checked to see if it is the root of a mount. If a
type is also given we are looking for a particular autofs mount and if
a match isn't found a fail is returned. If the the located path is the
root of a mount 1 is returned along with the super magic of the mount
or 0 otherwise.

8
Documentation/filesystems/ext3.txt
View File

@ -96,6 +96,11 @@ errors=remount-ro(*) Remount the filesystem read-only on an error.
errors=continue Keep going on a filesystem error.
errors=panic Panic and halt the machine if an error occurs.
data_err=ignore(*) Just print an error message if an error occurs
in a file data buffer in ordered mode.
data_err=abort Abort the journal if an error occurs in a file
data buffer in ordered mode.
grpid Give objects the same group ID as their creator.
bsdgroups
@ -193,6 +198,5 @@ kernel source: <file:fs/ext3/>
programs: http://e2fsprogs.sourceforge.net/
http://ext2resize.sourceforge.net
useful links: http://www.zip.com.au/~akpm/linux/ext3/ext3-usage.html
http://www-106.ibm.com/developerworks/linux/library/l-fs7/
useful links: http://www-106.ibm.com/developerworks/linux/library/l-fs7/
http://www-106.ibm.com/developerworks/linux/library/l-fs8/

51
Documentation/filesystems/ext4.txt
View File

@ -2,19 +2,24 @@
Ext4 Filesystem
===============
This is a development version of the ext4 filesystem, an advanced level
of the ext3 filesystem which incorporates scalability and reliability
enhancements for supporting large filesystems (64 bit) in keeping with
increasing disk capacities and state-of-the-art feature requirements.
Ext4 is an an advanced level of the ext3 filesystem which incorporates
scalability and reliability enhancements for supporting large filesystems
(64 bit) in keeping with increasing disk capacities and state-of-the-art
feature requirements.
Mailing list: linux-ext4@vger.kernel.org
Mailing list: linux-ext4@vger.kernel.org
Web site: http://ext4.wiki.kernel.org
1. Quick usage instructions:
===========================
Note: More extensive information for getting started with ext4 can be
found at the ext4 wiki site at the URL:
http://ext4.wiki.kernel.org/index.php/Ext4_Howto
- Compile and install the latest version of e2fsprogs (as of this
writing version 1.41) from:
writing version 1.41.3) from:
http://sourceforge.net/project/showfiles.php?group_id=2406
@ -32,28 +37,26 @@ Mailing list: linux-ext4@vger.kernel.org
you will need to merge your changes with the version from e2fsprogs
1.41.x.
- Create a new filesystem using the ext4dev filesystem type:
- Create a new filesystem using the ext4 filesystem type:
# mke2fs -t ext4dev /dev/hda1
# mke2fs -t ext4 /dev/hda1
Or configure an existing ext3 filesystem to support extents and set
the test_fs flag to indicate that it's ok for an in-development
filesystem to touch this filesystem:
Or to configure an existing ext3 filesystem to support extents:
# tune2fs -O extents -E test_fs /dev/hda1
# tune2fs -O extents /dev/hda1
If the filesystem was created with 128 byte inodes, it can be
converted to use 256 byte for greater efficiency via:
# tune2fs -I 256 /dev/hda1
(Note: we currently do not have tools to convert an ext4dev
(Note: we currently do not have tools to convert an ext4
filesystem back to ext3; so please do not do try this on production
filesystems.)
- Mounting:
# mount -t ext4dev /dev/hda1 /wherever
# mount -t ext4 /dev/hda1 /wherever
- When comparing performance with other filesystems, remember that
ext3/4 by default offers higher data integrity guarantees than most.
@ -104,8 +107,8 @@ exist yet so I'm not sure they're in the near-term roadmap.
The big performance win will come with mballoc, delalloc and flex_bg
grouping of bitmaps and inode tables. Some test results available here:
- http://www.bullopensource.org/ext4/20080530/ffsb-write-2.6.26-rc2.html
- http://www.bullopensource.org/ext4/20080530/ffsb-readwrite-2.6.26-rc2.html
- http://www.bullopensource.org/ext4/20080818-ffsb/ffsb-write-2.6.27-rc1.html
- http://www.bullopensource.org/ext4/20080818-ffsb/ffsb-readwrite-2.6.27-rc1.html
3. Options
==========
@ -177,6 +180,11 @@ barrier=<0|1(*)> This enables/disables the use of write barriers in
your disks are battery-backed in one way or another,
disabling barriers may safely improve performance.
inode_readahead=n This tuning parameter controls the maximum
number of inode table blocks that ext4's inode
table readahead algorithm will pre-read into
the buffer cache. The default value is 32 blocks.
orlov (*) This enables the new Orlov block allocator. It is
enabled by default.
@ -209,15 +217,17 @@ noreservation
bsddf (*) Make 'df' act like BSD.
minixdf Make 'df' act like Minix.
check=none Don't do extra checking of bitmaps on mount.
nocheck
debug Extra debugging information is sent to syslog.
errors=remount-ro(*) Remount the filesystem read-only on an error.
errors=continue Keep going on a filesystem error.
errors=panic Panic and halt the machine if an error occurs.
data_err=ignore(*) Just print an error message if an error occurs
in a file data buffer in ordered mode.
data_err=abort Abort the journal if an error occurs in a file
data buffer in ordered mode.
grpid Give objects the same group ID as their creator.
bsdgroups
@ -243,8 +253,6 @@ nobh (a) cache disk block mapping information
"nobh" option tries to avoid associating buffer
heads (supported only for "writeback" mode).
mballoc (*) Use the multiple block allocator for block allocation
nomballoc disabled multiple block allocator for block allocation.
stripe=n Number of filesystem blocks that mballoc will try
to use for allocation size and alignment. For RAID5/6
systems this should be the number of data
@ -252,6 +260,7 @@ stripe=n Number of filesystem blocks that mballoc will try
delalloc (*) Deferring block allocation until write-out time.
nodelalloc Disable delayed allocation. Blocks are allocation
when data is copied from user to page cache.
Data Mode
=========
There are 3 different data modes:

228
Documentation/filesystems/fiemap.txt Normal file
View File

@ -0,0 +1,228 @@
============
Fiemap Ioctl
============
The fiemap ioctl is an efficient method for userspace to get file
extent mappings. Instead of block-by-block mapping (such as bmap), fiemap
returns a list of extents.
Request Basics
--------------
A fiemap request is encoded within struct fiemap:
struct fiemap {
__u64 fm_start; /* logical offset (inclusive) at
* which to start mapping (in) */
__u64 fm_length; /* logical length of mapping which
* userspace cares about (in) */
__u32 fm_flags; /* FIEMAP_FLAG_* flags for request (in/out) */
__u32 fm_mapped_extents; /* number of extents that were
* mapped (out) */
__u32 fm_extent_count; /* size of fm_extents array (in) */
__u32 fm_reserved;
struct fiemap_extent fm_extents[0]; /* array of mapped extents (out) */
};
fm_start, and fm_length specify the logical range within the file
which the process would like mappings for. Extents returned mirror
those on disk - that is, the logical offset of the 1st returned extent
may start before fm_start, and the range covered by the last returned
extent may end after fm_length. All offsets and lengths are in bytes.
Certain flags to modify the way in which mappings are looked up can be
set in fm_flags. If the kernel doesn't understand some particular
flags, it will return EBADR and the contents of fm_flags will contain
the set of flags which caused the error. If the kernel is compatible
with all flags passed, the contents of fm_flags will be unmodified.
It is up to userspace to determine whether rejection of a particular
flag is fatal to it's operation. This scheme is intended to allow the
fiemap interface to grow in the future but without losing
compatibility with old software.
fm_extent_count specifies the number of elements in the fm_extents[] array
that can be used to return extents. If fm_extent_count is zero, then the
fm_extents[] array is ignored (no extents will be returned), and the
fm_mapped_extents count will hold the number of extents needed in
fm_extents[] to hold the file's current mapping. Note that there is
nothing to prevent the file from changing between calls to FIEMAP.
The following flags can be set in fm_flags:
* FIEMAP_FLAG_SYNC
If this flag is set, the kernel will sync the file before mapping extents.
* FIEMAP_FLAG_XATTR
If this flag is set, the extents returned will describe the inodes
extended attribute lookup tree, instead of it's data tree.
Extent Mapping
--------------
Extent information is returned within the embedded fm_extents array
which userspace must allocate along with the fiemap structure. The
number of elements in the fiemap_extents[] array should be passed via
fm_extent_count. The number of extents mapped by kernel will be
returned via fm_mapped_extents. If the number of fiemap_extents
allocated is less than would be required to map the requested range,
the maximum number of extents that can be mapped in the fm_extent[]
array will be returned and fm_mapped_extents will be equal to
fm_extent_count. In that case, the last extent in the array will not
complete the requested range and will not have the FIEMAP_EXTENT_LAST
flag set (see the next section on extent flags).
Each extent is described by a single fiemap_extent structure as
returned in fm_extents.
struct fiemap_extent {
__u64 fe_logical; /* logical offset in bytes for the start of
* the extent */
__u64 fe_physical; /* physical offset in bytes for the start
* of the extent */
__u64 fe_length; /* length in bytes for the extent */
__u64 fe_reserved64[2];
__u32 fe_flags; /* FIEMAP_EXTENT_* flags for this extent */
__u32 fe_reserved[3];
};
All offsets and lengths are in bytes and mirror those on disk. It is valid
for an extents logical offset to start before the request or it's logical
length to extend past the request. Unless FIEMAP_EXTENT_NOT_ALIGNED is
returned, fe_logical, fe_physical, and fe_length will be aligned to the
block size of the file system. With the exception of extents flagged as
FIEMAP_EXTENT_MERGED, adjacent extents will not be merged.
The fe_flags field contains flags which describe the extent returned.
A special flag, FIEMAP_EXTENT_LAST is always set on the last extent in
the file so that the process making fiemap calls can determine when no
more extents are available, without having to call the ioctl again.
Some flags are intentionally vague and will always be set in the
presence of other more specific flags. This way a program looking for
a general property does not have to know all existing and future flags
which imply that property.
For example, if FIEMAP_EXTENT_DATA_INLINE or FIEMAP_EXTENT_DATA_TAIL
are set, FIEMAP_EXTENT_NOT_ALIGNED will also be set. A program looking
for inline or tail-packed data can key on the specific flag. Software
which simply cares not to try operating on non-aligned extents
however, can just key on FIEMAP_EXTENT_NOT_ALIGNED, and not have to
worry about all present and future flags which might imply unaligned
data. Note that the opposite is not true - it would be valid for
FIEMAP_EXTENT_NOT_ALIGNED to appear alone.
* FIEMAP_EXTENT_LAST
This is the last extent in the file. A mapping attempt past this
extent will return nothing.
* FIEMAP_EXTENT_UNKNOWN
The location of this extent is currently unknown. This may indicate
the data is stored on an inaccessible volume or that no storage has
been allocated for the file yet.
* FIEMAP_EXTENT_DELALLOC
- This will also set FIEMAP_EXTENT_UNKNOWN.
Delayed allocation - while there is data for this extent, it's
physical location has not been allocated yet.
* FIEMAP_EXTENT_ENCODED
This extent does not consist of plain filesystem blocks but is
encoded (e.g. encrypted or compressed). Reading the data in this
extent via I/O to the block device will have undefined results.
Note that it is *always* undefined to try to update the data
in-place by writing to the indicated location without the
assistance of the filesystem, or to access the data using the
information returned by the FIEMAP interface while the filesystem
is mounted. In other words, user applications may only read the
extent data via I/O to the block device while the filesystem is
unmounted, and then only if the FIEMAP_EXTENT_ENCODED flag is
clear; user applications must not try reading or writing to the
filesystem via the block device under any other circumstances.
* FIEMAP_EXTENT_DATA_ENCRYPTED
- This will also set FIEMAP_EXTENT_ENCODED
The data in this extent has been encrypted by the file system.
* FIEMAP_EXTENT_NOT_ALIGNED
Extent offsets and length are not guaranteed to be block aligned.
* FIEMAP_EXTENT_DATA_INLINE
This will also set FIEMAP_EXTENT_NOT_ALIGNED
Data is located within a meta data block.
* FIEMAP_EXTENT_DATA_TAIL
This will also set FIEMAP_EXTENT_NOT_ALIGNED
Data is packed into a block with data from other files.
* FIEMAP_EXTENT_UNWRITTEN
Unwritten extent - the extent is allocated but it's data has not been
initialized. This indicates the extent's data will be all zero if read
through the filesystem but the contents are undefined if read directly from
the device.
* FIEMAP_EXTENT_MERGED
This will be set when a file does not support extents, i.e., it uses a block
based addressing scheme. Since returning an extent for each block back to
userspace would be highly inefficient, the kernel will try to merge most
adjacent blocks into 'extents'.
VFS -> File System Implementation
---------------------------------
File systems wishing to support fiemap must implement a ->fiemap callback on
their inode_operations structure. The fs ->fiemap call is responsible for
defining it's set of supported fiemap flags, and calling a helper function on
each discovered extent:
struct inode_operations {
...
int (*fiemap)(struct inode *, struct fiemap_extent_info *, u64 start,
u64 len);
->fiemap is passed struct fiemap_extent_info which describes the
fiemap request:
struct fiemap_extent_info {
unsigned int fi_flags; /* Flags as passed from user */
unsigned int fi_extents_mapped; /* Number of mapped extents */
unsigned int fi_extents_max; /* Size of fiemap_extent array */
struct fiemap_extent *fi_extents_start; /* Start of fiemap_extent array */
};
It is intended that the file system should not need to access any of this
structure directly.
Flag checking should be done at the beginning of the ->fiemap callback via the
fiemap_check_flags() helper:
int fiemap_check_flags(struct fiemap_extent_info *fieinfo, u32 fs_flags);
The struct fieinfo should be passed in as recieved from ioctl_fiemap(). The
set of fiemap flags which the fs understands should be passed via fs_flags. If
fiemap_check_flags finds invalid user flags, it will place the bad values in
fieinfo->fi_flags and return -EBADR. If the file system gets -EBADR, from
fiemap_check_flags(), it should immediately exit, returning that error back to
ioctl_fiemap().
For each extent in the request range, the file system should call
the helper function, fiemap_fill_next_extent():
int fiemap_fill_next_extent(struct fiemap_extent_info *info, u64 logical,
u64 phys, u64 len, u32 flags, u32 dev);
fiemap_fill_next_extent() will use the passed values to populate the
next free extent in the fm_extents array. 'General' extent flags will
automatically be set from specific flags on behalf of the calling file
system so that the userspace API is not broken.
fiemap_fill_next_extent() returns 0 on success, and 1 when the
user-supplied fm_extents array is full. If an error is encountered
while copying the extent to user memory, -EFAULT will be returned.

2
Documentation/filesystems/nfsroot.txt
View File

@ -169,7 +169,7 @@ They depend on various facilities being available:
3.1) Booting from a floppy using syslinux
When building kernels, an easy way to create a boot floppy that uses
syslinux is to use the zdisk or bzdisk make targets which use
syslinux is to use the zdisk or bzdisk make targets which use zimage
and bzimage images respectively. Both targets accept the
FDARGS parameter which can be used to set the kernel command line.

6
Documentation/filesystems/ocfs2.txt
View File

@ -76,3 +76,9 @@ localalloc=8(*) Allows custom localalloc size in MB. If the value is too
large, the fs will silently revert it to the default.
Localalloc is not enabled for local mounts.
localflocks This disables cluster aware flock.
inode64 Indicates that Ocfs2 is allowed to create inodes at
any location in the filesystem, including those which
will result in inode numbers occupying more than 32
bits of significance.
user_xattr (*) Enables Extended User Attributes.
nouser_xattr Disables Extended User Attributes.

114
Documentation/filesystems/proc.txt
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@ -923,45 +923,44 @@ CPUs.
The "procs_blocked" line gives the number of processes currently blocked,
waiting for I/O to complete.
1.9 Ext4 file system parameters
------------------------------
Ext4 file system have one directory per partition under /proc/fs/ext4/
# ls /proc/fs/ext4/hdc/
group_prealloc max_to_scan mb_groups mb_history min_to_scan order2_req
stats stream_req
mb_groups:
This file gives the details of multiblock allocator buddy cache of free blocks
Information about mounted ext4 file systems can be found in
/proc/fs/ext4. Each mounted filesystem will have a directory in
/proc/fs/ext4 based on its device name (i.e., /proc/fs/ext4/hdc or
/proc/fs/ext4/dm-0). The files in each per-device directory are shown
in Table 1-10, below.
mb_history:
Multiblock allocation history.
Table 1-10: Files in /proc/fs/ext4/<devname>
..............................................................................
File Content
mb_groups details of multiblock allocator buddy cache of free blocks
mb_history multiblock allocation history
stats controls whether the multiblock allocator should start
collecting statistics, which are shown during the unmount
group_prealloc the multiblock allocator will round up allocation
requests to a multiple of this tuning parameter if the
stripe size is not set in the ext4 superblock
max_to_scan The maximum number of extents the multiblock allocator
will search to find the best extent
min_to_scan The minimum number of extents the multiblock allocator
will search to find the best extent
order2_req Tuning parameter which controls the minimum size for
requests (as a power of 2) where the buddy cache is
used
stream_req Files which have fewer blocks than this tunable
parameter will have their blocks allocated out of a
block group specific preallocation pool, so that small
files are packed closely together. Each large file
will have its blocks allocated out of its own unique
preallocation pool.
inode_readahead Tuning parameter which controls the maximum number of
inode table blocks that ext4's inode table readahead
algorithm will pre-read into the buffer cache
..............................................................................
stats:
This file indicate whether the multiblock allocator should start collecting
statistics. The statistics are shown during unmount
group_prealloc:
The multiblock allocator normalize the block allocation request to
group_prealloc filesystem blocks if we don't have strip value set.
The stripe value can be specified at mount time or during mke2fs.
max_to_scan:
How long multiblock allocator can look for a best extent (in found extents)
min_to_scan:
How long multiblock allocator must look for a best extent
order2_req:
Multiblock allocator use 2^N search using buddies only for requests greater
than or equal to order2_req. The request size is specfied in file system
blocks. A value of 2 indicate only if the requests are greater than or equal
to 4 blocks.
stream_req:
Files smaller than stream_req are served by the stream allocator, whose
purpose is to pack requests as close each to other as possible to
produce smooth I/O traffic. Avalue of 16 indicate that file smaller than 16
filesystem block size will use group based preallocation.
------------------------------------------------------------------------------
Summary
@ -1322,6 +1321,18 @@ debugging information is displayed on console.
NMI switch that most IA32 servers have fires unknown NMI up, for example.
If a system hangs up, try pressing the NMI switch.
panic_on_unrecovered_nmi
------------------------
The default Linux behaviour on an NMI of either memory or unknown is to continue
operation. For many environments such as scientific computing it is preferable
that the box is taken out and the error dealt with than an uncorrected
parity/ECC error get propogated.
A small number of systems do generate NMI's for bizarre random reasons such as
power management so the default is off. That sysctl works like the existing
panic controls already in that directory.
nmi_watchdog
------------
@ -1332,13 +1343,6 @@ determine whether or not they are still functioning properly.
Because the NMI watchdog shares registers with oprofile, by disabling the NMI
watchdog, oprofile may have more registers to utilize.
maps_protect
------------
Enables/Disables the protection of the per-process proc entries "maps" and
"smaps". When enabled, the contents of these files are visible only to
readers that are allowed to ptrace() the given process.
msgmni
------
@ -1380,15 +1384,18 @@ causes the kernel to prefer to reclaim dentries and inodes.
dirty_background_ratio
----------------------
Contains, as a percentage of total system memory, the number of pages at which
the pdflush background writeback daemon will start writing out dirty data.
Contains, as a percentage of the dirtyable system memory (free pages + mapped
pages + file cache, not including locked pages and HugePages), the number of
pages at which the pdflush background writeback daemon will start writing out
dirty data.
dirty_ratio
-----------------
Contains, as a percentage of total system memory, the number of pages at which
a process which is generating disk writes will itself start writing out dirty
data.
Contains, as a percentage of the dirtyable system memory (free pages + mapped
pages + file cache, not including locked pages and HugePages), the number of
pages at which a process which is generating disk writes will itself start
writing out dirty data.
dirty_writeback_centisecs
-------------------------
@ -2408,24 +2415,29 @@ will be dumped when the <pid> process is dumped. coredump_filter is a bitmask
of memory types. If a bit of the bitmask is set, memory segments of the
corresponding memory type are dumped, otherwise they are not dumped.
The following 4 memory types are supported:
The following 7 memory types are supported:
- (bit 0) anonymous private memory
- (bit 1) anonymous shared memory
- (bit 2) file-backed private memory
- (bit 3) file-backed shared memory
- (bit 4) ELF header pages in file-backed private memory areas (it is
effective only if the bit 2 is cleared)
- (bit 5) hugetlb private memory
- (bit 6) hugetlb shared memory
Note that MMIO pages such as frame buffer are never dumped and vDSO pages
are always dumped regardless of the bitmask status.
Default value of coredump_filter is 0x3; this means all anonymous memory
segments are dumped.
Note bit 0-4 doesn't effect any hugetlb memory. hugetlb memory are only
effected by bit 5-6.
Default value of coredump_filter is 0x23; this means all anonymous memory
segments and hugetlb private memory are dumped.
If you don't want to dump all shared memory segments attached to pid 1234,
write 1 to the process's proc file.
write 0x21 to the process's proc file.
$ echo 0x1 > /proc/1234/coredump_filter
$ echo 0x21 > /proc/1234/coredump_filter
When a new process is created, the process inherits the bitmask status from its
parent. It is useful to set up coredump_filter before the program runs.

2
Documentation/filesystems/ramfs-rootfs-initramfs.txt
View File

@ -263,7 +263,7 @@ User Mode Linux, like so:
sleep(999999999);
}
EOF
gcc -static hello2.c -o init
gcc -static hello.c -o init
echo init | cpio -o -H newc | gzip > test.cpio.gz
# Testing external initramfs using the initrd loading mechanism.
qemu -kernel /boot/vmlinuz -initrd test.cpio.gz /dev/zero

9
Documentation/filesystems/ubifs.txt
View File

@ -86,6 +86,15 @@ norm_unmount (*) commit on unmount; the journal is committed
fast_unmount do not commit on unmount; this option makes
unmount faster, but the next mount slower
because of the need to replay the journal.
bulk_read read more in one go to take advantage of flash
media that read faster sequentially
no_bulk_read (*) do not bulk-read
no_chk_data_crc skip checking of CRCs on data nodes in order to
improve read performance. Use this option only
if the flash media is highly reliable. The effect
of this option is that corruption of the contents
of a file can go unnoticed.
chk_data_crc (*) do not skip checking CRCs on data nodes
Quick usage instructions

9
Documentation/gpio.txt
View File

@ -240,6 +240,10 @@ signal, or (b) something wrongly believes it's safe to remove drivers
needed to manage a signal that's in active use. That is, requesting a
GPIO can serve as a kind of lock.
Some platforms may also use knowledge about what GPIOs are active for
power management, such as by powering down unused chip sectors and, more
easily, gating off unused clocks.
These two calls are optional because not not all current Linux platforms
offer such functionality in their GPIO support; a valid implementation
could return success for all gpio_request() calls. Unlike the other calls,
@ -264,7 +268,7 @@ map between them using calls like:
/* map GPIO numbers to IRQ numbers */
int gpio_to_irq(unsigned gpio);
/* map IRQ numbers to GPIO numbers */
/* map IRQ numbers to GPIO numbers (avoid using this) */
int irq_to_gpio(unsigned irq);
Those return either the corresponding number in the other namespace, or
@ -284,7 +288,8 @@ system wakeup capabilities.
Non-error values returned from irq_to_gpio() would most commonly be used
with gpio_get_value(), for example to initialize or update driver state
when the IRQ is edge-triggered.
when the IRQ is edge-triggered. Note that some platforms don't support
this reverse mapping, so you should avoid using it.
Emulating Open Drain Signals

76
Documentation/hwmon/adt7470 Normal file
View File

@ -0,0 +1,76 @@
Kernel driver adt7470
=====================
Supported chips:
* Analog Devices ADT7470
Prefix: 'adt7470'
Addresses scanned: I2C 0x2C, 0x2E, 0x2F
Datasheet: Publicly available at the Analog Devices website
Author: Darrick J. Wong
Description
-----------
This driver implements support for the Analog Devices ADT7470 chip. There may
be other chips that implement this interface.
The ADT7470 uses the 2-wire interface compatible with the SMBus 2.0
specification. Using an analog to digital converter it measures up to ten (10)
external temperatures. It has four (4) 16-bit counters for measuring fan speed.
There are four (4) PWM outputs that can be used to control fan speed.
A sophisticated control system for the PWM outputs is designed into the ADT7470
that allows fan speed to be adjusted automatically based on any of the ten
temperature sensors. Each PWM output is individually adjustable and
programmable. Once configured, the ADT7470 will adjust the PWM outputs in
response to the measured temperatures with further host intervention. This
feature can also be disabled for manual control of the PWM's.
Each of the measured inputs (temperature, fan speed) has corresponding high/low
limit values. The ADT7470 will signal an ALARM if any measured value exceeds
either limit.
The ADT7470 DOES NOT sample all inputs continuously. A single pin on the
ADT7470 is connected to a multitude of thermal diodes, but the chip must be
instructed explicitly to read the multitude of diodes. If you want to use
automatic fan control mode, you must manually read any of the temperature
sensors or the fan control algorithm will not run. The chip WILL NOT DO THIS
AUTOMATICALLY; this must be done from userspace. This may be a bug in the chip
design, given that many other AD chips take care of this. The driver will not
read the registers more often than once every 5 seconds. Further,
configuration data is only read once per minute.
Special Features
----------------
The ADT7470 has a 8-bit ADC and is capable of measuring temperatures with 1
degC resolution.
The Analog Devices datasheet is very detailed and describes a procedure for
determining an optimal configuration for the automatic PWM control.
Configuration Notes
-------------------
Besides standard interfaces driver adds the following:
* PWM Control
* pwm#_auto_point1_pwm and pwm#_auto_point1_temp and
* pwm#_auto_point2_pwm and pwm#_auto_point2_temp -
point1: Set the pwm speed at a lower temperature bound.
point2: Set the pwm speed at a higher temperature bound.
The ADT7470 will scale the pwm between the lower and higher pwm speed when
the temperature is between the two temperature boundaries. PWM values range
from 0 (off) to 255 (full speed). Fan speed will be set to maximum when the
temperature sensor associated with the PWM control exceeds
pwm#_auto_point2_temp.
Notes
-----
As stated above, the temperature inputs must be read periodically from
userspace in order for the automatic pwm algorithm to run.

18
Documentation/hwmon/adt7473
View File

@ -14,14 +14,14 @@ Description
This driver implements support for the Analog Devices ADT7473 chip family.
The LM85 uses the 2-wire interface compatible with the SMBUS 2.0
The ADT7473 uses the 2-wire interface compatible with the SMBUS 2.0
specification. Using an analog to digital converter it measures three (3)
temperatures and two (2) voltages. It has three (3) 16-bit counters for
temperatures and two (2) voltages. It has four (4) 16-bit counters for
measuring fan speed. There are three (3) PWM outputs that can be used
to control fan speed.
A sophisticated control system for the PWM outputs is designed into the
LM85 that allows fan speed to be adjusted automatically based on any of the
ADT7473 that allows fan speed to be adjusted automatically based on any of the
three temperature sensors. Each PWM output is individually adjustable and
programmable. Once configured, the ADT7473 will adjust the PWM outputs in
response to the measured temperatures without further host intervention.
@ -46,14 +46,6 @@ from the raw value to get the temperature value.
The Analog Devices datasheet is very detailed and describes a procedure for
determining an optimal configuration for the automatic PWM control.
Hardware Configurations
-----------------------
The ADT7473 chips have an optional SMBALERT output that can be used to
signal the chipset in case a limit is exceeded or the temperature sensors
fail. Individual sensor interrupts can be masked so they won't trigger
SMBALERT. The SMBALERT output if configured replaces the PWM2 function.
Configuration Notes
-------------------
@ -61,8 +53,8 @@ Besides standard interfaces driver adds the following:
* PWM Control
* pwm#_auto_point1_pwm and pwm#_auto_point1_temp and
* pwm#_auto_point2_pwm and pwm#_auto_point2_temp -
* pwm#_auto_point1_pwm and temp#_auto_point1_temp and
* pwm#_auto_point2_pwm and temp#_auto_point2_temp -
point1: Set the pwm speed at a lower temperature bound.
point2: Set the pwm speed at a higher temperature bound.

4
Documentation/hwmon/it87
View File

@ -136,10 +136,10 @@ once-only alarms.
The IT87xx only updates its values each 1.5 seconds; reading it more often
will do no harm, but will return 'old' values.
To change sensor N to a thermistor, 'echo 2 > tempN_type' where N is 1, 2,
To change sensor N to a thermistor, 'echo 4 > tempN_type' where N is 1, 2,
or 3. To change sensor N to a thermal diode, 'echo 3 > tempN_type'.
Give 0 for unused sensor. Any other value is invalid. To configure this at
startup, consult lm_sensors's /etc/sensors.conf. (2 = thermistor;
startup, consult lm_sensors's /etc/sensors.conf. (4 = thermistor;
3 = thermal diode)

10
Documentation/hwmon/lm85
View File

@ -163,16 +163,6 @@ configured individually according to the following options.
* pwm#_auto_pwm_min - this specifies the PWM value for temp#_auto_temp_off
temperature. (PWM value from 0 to 255)
* pwm#_auto_pwm_freq - select base frequency of PWM output. You can select
in range of 10.0 to 94.0 Hz in .1 Hz units.
(Values 100 to 940).
The pwm#_auto_pwm_freq can be set to one of the following 8 values. Setting the
frequency to a value not on this list, will result in the next higher frequency
being selected. The actual device frequency may vary slightly from this
specification as designed by the manufacturer. Consult the datasheet for more
details. (PWM Frequency values: 100, 150, 230, 300, 380, 470, 620, 940)
* pwm#_auto_pwm_minctl - this flags selects for temp#_auto_temp_off temperature
the bahaviour of fans. Write 1 to let fans spinning at
pwm#_auto_pwm_min or write 0 to let them off.

9
Documentation/hwmon/lm87
View File

@ -65,11 +65,10 @@ The LM87 has four pins which can serve one of two possible functions,
depending on the hardware configuration.
Some functions share pins, so not all functions are available at the same
time. Which are depends on the hardware setup. This driver assumes that
the BIOS configured the chip correctly. In that respect, it differs from
the original driver (from lm_sensors for Linux 2.4), which would force the
LM87 to an arbitrary, compile-time chosen mode, regardless of the actual
chipset wiring.
time. Which are depends on the hardware setup. This driver normally
assumes that firmware configured the chip correctly. Where this is not
the case, platform code must set the I2C client's platform_data to point
to a u8 value to be written to the channel register.
For reference, here is the list of exclusive functions:
- in0+in5 (default) or temp3

45
Documentation/hwmon/lm90
View File

@ -11,7 +11,7 @@ Supported chips:
Prefix: 'lm99'
Addresses scanned: I2C 0x4c and 0x4d
Datasheet: Publicly available at the National Semiconductor website
http://www.national.com/pf/LM/LM89.html
http://www.national.com/mpf/LM/LM89.html
* National Semiconductor LM99
Prefix: 'lm99'
Addresses scanned: I2C 0x4c and 0x4d
@ -21,18 +21,32 @@ Supported chips:
Prefix: 'lm86'
Addresses scanned: I2C 0x4c
Datasheet: Publicly available at the National Semiconductor website
http://www.national.com/pf/LM/LM86.html
http://www.national.com/mpf/LM/LM86.html
* Analog Devices ADM1032
Prefix: 'adm1032'
Addresses scanned: I2C 0x4c and 0x4d
Datasheet: Publicly available at the Analog Devices website
http://www.analog.com/en/prod/0,2877,ADM1032,00.html
Datasheet: Publicly available at the ON Semiconductor website
http://www.onsemi.com/PowerSolutions/product.do?id=ADM1032
* Analog Devices ADT7461
Prefix: 'adt7461'
Addresses scanned: I2C 0x4c and 0x4d
Datasheet: Publicly available at the Analog Devices website
http://www.analog.com/en/prod/0,2877,ADT7461,00.html
Note: Only if in ADM1032 compatibility mode
Datasheet: Publicly available at the ON Semiconductor website
http://www.onsemi.com/PowerSolutions/product.do?id=ADT7461
* Maxim MAX6646
Prefix: 'max6646'
Addresses scanned: I2C 0x4d
Datasheet: Publicly available at the Maxim website
http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3497
* Maxim MAX6647
Prefix: 'max6646'
Addresses scanned: I2C 0x4e
Datasheet: Publicly available at the Maxim website
http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3497
* Maxim MAX6649
Prefix: 'max6646'
Addresses scanned: I2C 0x4c
Datasheet: Publicly available at the Maxim website
http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3497
* Maxim MAX6657
Prefix: 'max6657'
Addresses scanned: I2C 0x4c
@ -70,25 +84,21 @@ Description
The LM90 is a digital temperature sensor. It senses its own temperature as
well as the temperature of up to one external diode. It is compatible
with many other devices such as the LM86, the LM89, the LM99, the ADM1032,
the MAX6657, MAX6658, MAX6659, MAX6680 and the MAX6681 all of which are
supported by this driver.
with many other devices, many of which are supported by this driver.
Note that there is no easy way to differentiate between the MAX6657,
MAX6658 and MAX6659 variants. The extra address and features of the
MAX6659 are not supported by this driver. The MAX6680 and MAX6681 only
differ in their pinout, therefore they obviously can't (and don't need to)
be distinguished. Additionally, the ADT7461 is supported if found in
ADM1032 compatibility mode.
be distinguished.
The specificity of this family of chipsets over the ADM1021/LM84
family is that it features critical limits with hysteresis, and an
increased resolution of the remote temperature measurement.
The different chipsets of the family are not strictly identical, although
very similar. This driver doesn't handle any specific feature for now,
with the exception of SMBus PEC. For reference, here comes a non-exhaustive
list of specific features:
very similar. For reference, here comes a non-exhaustive list of specific
features:
LM90:
* Filter and alert configuration register at 0xBF.
@ -114,9 +124,11 @@ ADT7461:
* Lower resolution for remote temperature
MAX6657 and MAX6658:
* Better local resolution
* Remote sensor type selection
MAX6659:
* Better local resolution
* Selectable address
* Second critical temperature limit
* Remote sensor type selection
@ -127,7 +139,8 @@ MAX6680 and MAX6681:
All temperature values are given in degrees Celsius. Resolution
is 1.0 degree for the local temperature, 0.125 degree for the remote
temperature.
temperature, except for the MAX6657, MAX6658 and MAX6659 which have a
resolution of 0.125 degree for both temperatures.
Each sensor has its own high and low limits, plus a critical limit.
Additionally, there is a relative hysteresis value common to both critical

7
Documentation/hwmon/pc87360
View File

@ -5,12 +5,7 @@ Supported chips:
* National Semiconductor PC87360, PC87363, PC87364, PC87365 and PC87366
Prefixes: 'pc87360', 'pc87363', 'pc87364', 'pc87365', 'pc87366'
Addresses scanned: none, address read from Super I/O config space
Datasheets:
http://www.national.com/pf/PC/PC87360.html
http://www.national.com/pf/PC/PC87363.html
http://www.national.com/pf/PC/PC87364.html
http://www.national.com/pf/PC/PC87365.html
http://www.national.com/pf/PC/PC87366.html
Datasheets: No longer available
Authors: Jean Delvare <khali@linux-fr.org>

2
Documentation/hwmon/pc87427
View File

@ -5,7 +5,7 @@ Supported chips:
* National Semiconductor PC87427
Prefix: 'pc87427'
Addresses scanned: none, address read from Super I/O config space
Datasheet: http://www.winbond.com.tw/E-WINBONDHTM/partner/apc_007.html
Datasheet: No longer available
Author: Jean Delvare <khali@linux-fr.org>

12
Documentation/hwmon/sysfs-interface
View File

@ -329,6 +329,10 @@ power[1-*]_average Average power use
Unit: microWatt
RO
power[1-*]_average_interval Power use averaging interval
Unit: milliseconds
RW
power[1-*]_average_highest Historical average maximum power use
Unit: microWatt
RO
@ -353,6 +357,14 @@ power[1-*]_reset_history Reset input_highest, input_lowest,
average_highest and average_lowest.
WO
**********
* Energy *
**********
energy[1-*]_input Cumulative energy use
Unit: microJoule
RO
**********
* Alarms *
**********

37
Documentation/hwmon/w83781d
View File

@ -353,7 +353,7 @@ in6=255
# PWM
Additional info about PWM on the AS99127F (may apply to other Asus
* Additional info about PWM on the AS99127F (may apply to other Asus
chips as well) by Jean Delvare as of 2004-04-09:
AS99127F revision 2 seems to have two PWM registers at 0x59 and 0x5A,
@ -396,7 +396,7 @@ Please contact us if you can figure out how it is supposed to work. As
long as we don't know more, the w83781d driver doesn't handle PWM on
AS99127F chips at all.
Additional info about PWM on the AS99127F rev.1 by Hector Martin:
* Additional info about PWM on the AS99127F rev.1 by Hector Martin:
I've been fiddling around with the (in)famous 0x59 register and
found out the following values do work as a form of coarse pwm:
@ -418,3 +418,36 @@ change.
My mobo is an ASUS A7V266-E. This behavior is similar to what I got
with speedfan under Windows, where 0-15% would be off, 15-2x% (can't
remember the exact value) would be 70% and higher would be full on.
* Additional info about PWM on the AS99127F rev.1 from lm-sensors
ticket #2350:
I conducted some experiment on Asus P3B-F motherboard with AS99127F
(Ver. 1).
I confirm that 0x59 register control the CPU_Fan Header on this
motherboard, and 0x5a register control PWR_Fan.
In order to reduce the dependency of specific fan, the measurement is
conducted with a digital scope without fan connected. I found out that
P3B-F actually output variable DC voltage on fan header center pin,
looks like PWM is filtered on this motherboard.
Here are some of measurements:
0x80 20 mV
0x81 20 mV
0x82 232 mV
0x83 1.2 V
0x84 2.31 V
0x85 3.44 V
0x86 4.62 V
0x87 5.81 V
0x88 7.01 V
9x89 8.22 V
0x8a 9.42 V
0x8b 10.6 V
0x8c 11.9 V
0x8d 12.4 V
0x8e 12.4 V
0x8f 12.4 V

43
Documentation/hwmon/w83791d
View File

@ -58,29 +58,35 @@ internal state that allows no clean access (Bank with ID register is not
currently selected). If you know the address of the chip, use a 'force'
parameter; this will put it into a more well-behaved state first.
The driver implements three temperature sensors, five fan rotation speed
sensors, and ten voltage sensors.
The driver implements three temperature sensors, ten voltage sensors,
five fan rotation speed sensors and manual PWM control of each fan.
Temperatures are measured in degrees Celsius and measurement resolution is 1
degC for temp1 and 0.5 degC for temp2 and temp3. An alarm is triggered when
the temperature gets higher than the Overtemperature Shutdown value; it stays
on until the temperature falls below the Hysteresis value.
Voltage sensors (also known as IN sensors) report their values in millivolts.
An alarm is triggered if the voltage has crossed a programmable minimum
or maximum limit.
Fan rotation speeds are reported in RPM (rotations per minute). An alarm is
triggered if the rotation speed has dropped below a programmable limit. Fan
readings can be divided by a programmable divider (1, 2, 4, 8, 16,
32, 64 or 128 for all fans) to give the readings more range or accuracy.
Voltage sensors (also known as IN sensors) report their values in millivolts.
An alarm is triggered if the voltage has crossed a programmable minimum
or maximum limit.
Each fan controlled is controlled by PWM. The PWM duty cycle can be read and
set for each fan separately. Valid values range from 0 (stop) to 255 (full).
PWM 1-3 support Thermal Cruise mode, in which the PWMs are automatically
regulated to keep respectively temp 1-3 at a certain target temperature.
See below for the description of the sysfs-interface.
The w83791d has a global bit used to enable beeping from the speaker when an
alarm is triggered as well as a bitmask to enable or disable the beep for
specific alarms. You need both the global beep enable bit and the
corresponding beep bit to be on for a triggered alarm to sound a beep.
The sysfs interface to the gloabal enable is via the sysfs beep_enable file.
The sysfs interface to the global enable is via the sysfs beep_enable file.
This file is used for both legacy and new code.
The sysfs interface to the beep bitmask has migrated from the original legacy
@ -105,6 +111,27 @@ going forward.
The driver reads the hardware chip values at most once every three seconds.
User mode code requesting values more often will receive cached values.
/sys files
----------
The sysfs-interface is documented in the 'sysfs-interface' file. Only
chip-specific options are documented here.
pwm[1-3]_enable - this file controls mode of fan/temperature control for
fan 1-3. Fan/PWM 4-5 only support manual mode.
* 1 Manual mode
* 2 Thermal Cruise mode
* 3 Fan Speed Cruise mode (no further support)
temp[1-3]_target - defines the target temperature for Thermal Cruise mode.
Unit: millidegree Celsius
RW
temp[1-3]_tolerance - temperature tolerance for Thermal Cruise mode.
Specifies an interval around the target temperature
in which the fan speed is not changed.
Unit: millidegree Celsius
RW
Alarms bitmap vs. beep_mask bitmask
------------------------------------
For legacy code using the alarms and beep_mask files:
@ -132,7 +159,3 @@ tart2 : alarms: 0x020000 beep_mask: 0x080000 <== mismatch
tart3 : alarms: 0x040000 beep_mask: 0x100000 <== mismatch
case_open : alarms: 0x001000 beep_mask: 0x001000
global_enable: alarms: -------- beep_mask: 0x800000 (modified via beep_enable)
W83791D TODO:
---------------
Provide a patch for smart-fan control (still need appropriate motherboard/fans)

8
Documentation/i2c/busses/i2c-viapro
View File

@ -16,6 +16,9 @@ Supported adapters:
* VIA Technologies, Inc. CX700
Datasheet: available on request and under NDA from VIA
* VIA Technologies, Inc. VX800/VX820
Datasheet: available on http://linux.via.com.tw
Authors:
Kyösti Mälkki <kmalkki@cc.hut.fi>,
Mark D. Studebaker <mdsxyz123@yahoo.com>,
@ -49,6 +52,7 @@ Your lspci -n listing must show one of these :
device 1106:3372 (VT8237S)
device 1106:3287 (VT8251)
device 1106:8324 (CX700)
device 1106:8353 (VX800/VX820)
If none of these show up, you should look in the BIOS for settings like
enable ACPI / SMBus or even USB.
@ -57,5 +61,5 @@ Except for the oldest chips (VT82C596A/B, VT82C686A and most probably
VT8231), this driver supports I2C block transactions. Such transactions
are mainly useful to read from and write to EEPROMs.
The CX700 additionally appears to support SMBus PEC, although this driver
doesn't implement it yet.
The CX700/VX800/VX820 additionally appears to support SMBus PEC, although
this driver doesn't implement it yet.

110
Documentation/i2c/dev-interface
View File

@ -4,6 +4,10 @@ the /dev interface. You need to load module i2c-dev for this.
Each registered i2c adapter gets a number, counting from 0. You can
examine /sys/class/i2c-dev/ to see what number corresponds to which adapter.
Alternatively, you can run "i2cdetect -l" to obtain a formated list of all
i2c adapters present on your system at a given time. i2cdetect is part of
the i2c-tools package.
I2C device files are character device files with major device number 89
and a minor device number corresponding to the number assigned as
explained above. They should be called "i2c-%d" (i2c-0, i2c-1, ...,
@ -17,30 +21,34 @@ So let's say you want to access an i2c adapter from a C program. The
first thing to do is "#include <linux/i2c-dev.h>". Please note that
there are two files named "i2c-dev.h" out there, one is distributed
with the Linux kernel and is meant to be included from kernel
driver code, the other one is distributed with lm_sensors and is
driver code, the other one is distributed with i2c-tools and is
meant to be included from user-space programs. You obviously want
the second one here.
Now, you have to decide which adapter you want to access. You should
inspect /sys/class/i2c-dev/ to decide this. Adapter numbers are assigned
somewhat dynamically, so you can not even assume /dev/i2c-0 is the
first adapter.
inspect /sys/class/i2c-dev/ or run "i2cdetect -l" to decide this.
Adapter numbers are assigned somewhat dynamically, so you can not
assume much about them. They can even change from one boot to the next.
Next thing, open the device file, as follows:
int file;
int adapter_nr = 2; /* probably dynamically determined */
char filename[20];
sprintf(filename,"/dev/i2c-%d",adapter_nr);
if ((file = open(filename,O_RDWR)) < 0) {
snprintf(filename, 19, "/dev/i2c-%d", adapter_nr);
file = open(filename, O_RDWR);
if (file < 0) {
/* ERROR HANDLING; you can check errno to see what went wrong */
exit(1);
}
When you have opened the device, you must specify with what device
address you want to communicate:
int addr = 0x40; /* The I2C address */
if (ioctl(file,I2C_SLAVE,addr) < 0) {
if (ioctl(file, I2C_SLAVE, addr) < 0) {
/* ERROR HANDLING; you can check errno to see what went wrong */
exit(1);
}
@ -48,31 +56,41 @@ address you want to communicate:
Well, you are all set up now. You can now use SMBus commands or plain
I2C to communicate with your device. SMBus commands are preferred if
the device supports them. Both are illustrated below.
__u8 register = 0x10; /* Device register to access */
__s32 res;
char buf[10];
/* Using SMBus commands */
res = i2c_smbus_read_word_data(file,register);
res = i2c_smbus_read_word_data(file, register);
if (res < 0) {
/* ERROR HANDLING: i2c transaction failed */
} else {
/* res contains the read word */
}
/* Using I2C Write, equivalent of
i2c_smbus_write_word_data(file,register,0x6543) */
i2c_smbus_write_word_data(file, register, 0x6543) */
buf[0] = register;
buf[1] = 0x43;
buf[2] = 0x65;
if ( write(file,buf,3) != 3) {
if (write(file, buf, 3) ! =3) {
/* ERROR HANDLING: i2c transaction failed */
}
/* Using I2C Read, equivalent of i2c_smbus_read_byte(file) */
if (read(file,buf,1) != 1) {
if (read(file, buf, 1) != 1) {
/* ERROR HANDLING: i2c transaction failed */
} else {
/* buf[0] contains the read byte */
}
Note that only a subset of the I2C and SMBus protocols can be achieved by
the means of read() and write() calls. In particular, so-called combined
transactions (mixing read and write messages in the same transaction)
aren't supported. For this reason, this interface is almost never used by
user-space programs.
IMPORTANT: because of the use of inline functions, you *have* to use
'-O' or some variation when you compile your program!
@ -80,31 +98,29 @@ IMPORTANT: because of the use of inline functions, you *have* to use
Full interface description
==========================
The following IOCTLs are defined and fully supported
(see also i2c-dev.h):
The following IOCTLs are defined:
ioctl(file,I2C_SLAVE,long addr)
ioctl(file, I2C_SLAVE, long addr)
Change slave address. The address is passed in the 7 lower bits of the
argument (except for 10 bit addresses, passed in the 10 lower bits in this
case).
ioctl(file,I2C_TENBIT,long select)
ioctl(file, I2C_TENBIT, long select)
Selects ten bit addresses if select not equals 0, selects normal 7 bit
addresses if select equals 0. Default 0. This request is only valid
if the adapter has I2C_FUNC_10BIT_ADDR.
ioctl(file,I2C_PEC,long select)
ioctl(file, I2C_PEC, long select)
Selects SMBus PEC (packet error checking) generation and verification
if select not equals 0, disables if select equals 0. Default 0.
Used only for SMBus transactions. This request only has an effect if the
the adapter has I2C_FUNC_SMBUS_PEC; it is still safe if not, it just
doesn't have any effect.
ioctl(file,I2C_FUNCS,unsigned long *funcs)
ioctl(file, I2C_FUNCS, unsigned long *funcs)
Gets the adapter functionality and puts it in *funcs.
ioctl(file,I2C_RDWR,struct i2c_rdwr_ioctl_data *msgset)
ioctl(file, I2C_RDWR, struct i2c_rdwr_ioctl_data *msgset)
Do combined read/write transaction without stop in between.
Only valid if the adapter has I2C_FUNC_I2C. The argument is
a pointer to a
@ -120,10 +136,9 @@ ioctl(file,I2C_RDWR,struct i2c_rdwr_ioctl_data *msgset)
The slave address and whether to use ten bit address mode has to be
set in each message, overriding the values set with the above ioctl's.
Other values are NOT supported at this moment, except for I2C_SMBUS,
which you should never directly call; instead, use the access functions
below.
ioctl(file, I2C_SMBUS, struct i2c_smbus_ioctl_data *args)
Not meant to be called directly; instead, use the access functions
below.
You can do plain i2c transactions by using read(2) and write(2) calls.
You do not need to pass the address byte; instead, set it through
@ -148,7 +163,52 @@ what happened. The 'write' transactions return 0 on success; the
returns the number of values read. The block buffers need not be longer
than 32 bytes.
The above functions are all macros, that resolve to calls to the
i2c_smbus_access function, that on its turn calls a specific ioctl
The above functions are all inline functions, that resolve to calls to
the i2c_smbus_access function, that on its turn calls a specific ioctl
with the data in a specific format. Read the source code if you
want to know what happens behind the screens.
Implementation details
======================
For the interested, here's the code flow which happens inside the kernel
when you use the /dev interface to I2C:
1* Your program opens /dev/i2c-N and calls ioctl() on it, as described in
section "C example" above.
2* These open() and ioctl() calls are handled by the i2c-dev kernel
driver: see i2c-dev.c:i2cdev_open() and i2c-dev.c:i2cdev_ioctl(),
respectively. You can think of i2c-dev as a generic I2C chip driver
that can be programmed from user-space.
3* Some ioctl() calls are for administrative tasks and are handled by
i2c-dev directly. Examples include I2C_SLAVE (set the address of the
device you want to access) and I2C_PEC (enable or disable SMBus error
checking on future transactions.)
4* Other ioctl() calls are converted to in-kernel function calls by
i2c-dev. Examples include I2C_FUNCS, which queries the I2C adapter
functionality using i2c.h:i2c_get_functionality(), and I2C_SMBUS, which
performs an SMBus transaction using i2c-core.c:i2c_smbus_xfer().
The i2c-dev driver is responsible for checking all the parameters that
come from user-space for validity. After this point, there is no
difference between these calls that came from user-space through i2c-dev
and calls that would have been performed by kernel I2C chip drivers
directly. This means that I2C bus drivers don't need to implement
anything special to support access from user-space.
5* These i2c-core.c/i2c.h functions are wrappers to the actual
implementation of your I2C bus driver. Each adapter must declare
callback functions implementing these standard calls.
i2c.h:i2c_get_functionality() calls i2c_adapter.algo->functionality(),
while i2c-core.c:i2c_smbus_xfer() calls either
adapter.algo->smbus_xfer() if it is implemented, or if not,
i2c-core.c:i2c_smbus_xfer_emulated() which in turn calls
i2c_adapter.algo->master_xfer().
After your I2C bus driver has processed these requests, execution runs
up the call chain, with almost no processing done, except by i2c-dev to
package the returned data, if any, in suitable format for the ioctl.

4
Documentation/i2c/smbus-protocol
View File

@ -109,8 +109,8 @@ specified through the Comm byte.
S Addr Wr [A] Comm [A] DataLow [A] DataHigh [A] P
SMBus Process Call
==================
SMBus Process Call: i2c_smbus_process_call()
=============================================
This command selects a device register (through the Comm byte), sends
16 bits of data to it, and reads 16 bits of data in return.

4
Documentation/i2c/writing-clients
View File

@ -606,6 +606,8 @@ SMBus communication
extern s32 i2c_smbus_read_word_data(struct i2c_client * client, u8 command);
extern s32 i2c_smbus_write_word_data(struct i2c_client * client,
u8 command, u16 value);
extern s32 i2c_smbus_process_call(struct i2c_client *client,
u8 command, u16 value);
extern s32 i2c_smbus_read_block_data(struct i2c_client * client,
u8 command, u8 *values);
extern s32 i2c_smbus_write_block_data(struct i2c_client * client,
@ -621,8 +623,6 @@ These ones were removed from i2c-core because they had no users, but could
be added back later if needed:
extern s32 i2c_smbus_write_quick(struct i2c_client * client, u8 value);
extern s32 i2c_smbus_process_call(struct i2c_client * client,
u8 command, u16 value);
extern s32 i2c_smbus_block_process_call(struct i2c_client *client,
u8 command, u8 length,
u8 *values)

9
Documentation/ia64/kvm.txt
View File

@ -1,7 +1,8 @@
Currently, kvm module in EXPERIMENTAL stage on IA64. This means that
interfaces are not stable enough to use. So, plase had better don't run
critical applications in virtual machine. We will try our best to make it
strong in future versions!
Currently, kvm module is in EXPERIMENTAL stage on IA64. This means that
interfaces are not stable enough to use. So, please don't run critical
applications in virtual machine.
We will try our best to improve it in future versions!
Guide: How to boot up guests on kvm/ia64
This guide is to describe how to enable kvm support for IA-64 systems.

3
Documentation/ioctl-number.txt
View File

@ -92,6 +92,7 @@ Code Seq# Include File Comments
'J' 00-1F drivers/scsi/gdth_ioctl.h
'K' all linux/kd.h
'L' 00-1F linux/loop.h
'L' 20-2F driver/usb/misc/vstusb.h
'L' E0-FF linux/ppdd.h encrypted disk device driver
<http://linux01.gwdg.de/~alatham/ppdd.html>
'M' all linux/soundcard.h
@ -110,6 +111,8 @@ Code Seq# Include File Comments
'W' 00-1F linux/wanrouter.h conflict!
'X' all linux/xfs_fs.h
'Y' all linux/cyclades.h
'[' 00-07 linux/usb/usbtmc.h USB Test and Measurement Devices
<mailto:gregkh@suse.de>
'a' all ATM on linux
<http://lrcwww.epfl.ch/linux-atm/magic.html>
'b' 00-FF bit3 vme host bridge

4
Documentation/kernel-doc-nano-HOWTO.txt
View File

@ -168,10 +168,10 @@ if ($#ARGV < 0) {
mkdir $ARGV[0],0777;
$state = 0;
while (<STDIN>) {
if (/^\.TH \"[^\"]*\" 4 \"([^\"]*)\"/) {
if (/^\.TH \"[^\"]*\" 9 \"([^\"]*)\"/) {
if ($state == 1) { close OUT }
$state = 1;
$fn = "$ARGV[0]/$1.4";
$fn = "$ARGV[0]/$1.9";
print STDERR "Creating $fn\n";
open OUT, ">$fn" or die "can't open $fn: $!\n";
print OUT $_;

123
Documentation/kernel-parameters.txt
View File

@ -101,6 +101,7 @@ parameter is applicable:
X86-64 X86-64 architecture is enabled.
More X86-64 boot options can be found in
Documentation/x86_64/boot-options.txt .
X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
In addition, the following text indicates that the option:
@ -284,6 +285,11 @@ and is between 256 and 4096 characters. It is defined in the file
isolate - enable device isolation (each device, as far
as possible, will get its own protection
domain)
fullflush - enable flushing of IO/TLB entries when
they are unmapped. Otherwise they are
flushed before they will be reused, which
is a lot of faster
amd_iommu_size= [HW,X86-64]
Define the size of the aperture for the AMD IOMMU
driver. Possible values are:
@ -463,12 +469,6 @@ and is between 256 and 4096 characters. It is defined in the file
Range: 0 - 8192
Default: 64
disable_8254_timer
enable_8254_timer
[IA32/X86_64] Disable/Enable interrupt 0 timer routing
over the 8254 in addition to over the IO-APIC. The
kernel tries to set a sensible default.
hpet= [X86-32,HPET] option to control HPET usage
Format: { enable (default) | disable | force }
disable: disable HPET and use PIT instead
@ -659,11 +659,12 @@ and is between 256 and 4096 characters. It is defined in the file
earlyprintk= [X86-32,X86-64,SH,BLACKFIN]
earlyprintk=vga
earlyprintk=serial[,ttySn[,baudrate]]
earlyprintk=dbgp
Append ",keep" to not disable it when the real console
takes over.
Only vga or serial at a time, not both.
Only vga or serial or usb debug port at a time.
Currently only ttyS0 and ttyS1 are supported.
@ -690,7 +691,7 @@ and is between 256 and 4096 characters. It is defined in the file
See Documentation/block/as-iosched.txt and
Documentation/block/deadline-iosched.txt for details.
elfcorehdr= [X86-32, X86_64]
elfcorehdr= [IA64,PPC,SH,X86-32,X86_64]
Specifies physical address of start of kernel core
image elf header. Generally kexec loader will
pass this option to capture kernel.
@ -796,6 +797,9 @@ and is between 256 and 4096 characters. It is defined in the file
Defaults to the default architecture's huge page size
if not specified.
hlt [BUGS=ARM,SH]
i8042.debug [HW] Toggle i8042 debug mode
i8042.direct [HW] Put keyboard port into non-translated mode
i8042.dumbkbd [HW] Pretend that controller can only read data from
keyboard and cannot control its state
@ -1020,6 +1024,10 @@ and is between 256 and 4096 characters. It is defined in the file
(only serial suported for now)
Format: <serial_device>[,baud]
kmac= [MIPS] korina ethernet MAC address.
Configure the RouterBoard 532 series on-chip
Ethernet adapter MAC address.
l2cr= [PPC]
l3cr= [PPC]
@ -1206,6 +1214,10 @@ and is between 256 and 4096 characters. It is defined in the file
mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
memory.
memchunk=nn[KMG]
[KNL,SH] Allow user to override the default size for
per-device physically contiguous DMA buffers.
memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
E820 memory map, as specified by the user.
Such memmap=exactmap lines can be constructed based on
@ -1228,6 +1240,29 @@ and is between 256 and 4096 characters. It is defined in the file
or
memmap=0x10000$0x18690000
memory_corruption_check=0/1 [X86]
Some BIOSes seem to corrupt the first 64k of
memory when doing things like suspend/resume.
Setting this option will scan the memory
looking for corruption. Enabling this will
both detect corruption and prevent the kernel
from using the memory being corrupted.
However, its intended as a diagnostic tool; if
repeatable BIOS-originated corruption always
affects the same memory, you can use memmap=
to prevent the kernel from using that memory.
memory_corruption_check_size=size [X86]
By default it checks for corruption in the low
64k, making this memory unavailable for normal
use. Use this parameter to scan for
corruption in more or less memory.
memory_corruption_check_period=seconds [X86]
By default it checks for corruption every 60
seconds. Use this parameter to check at some
other rate. 0 disables periodic checking.
memtest= [KNL,X86] Enable memtest
Format: <integer>
range: 0,4 : pattern number
@ -1365,6 +1400,8 @@ and is between 256 and 4096 characters. It is defined in the file
nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
nodsp [SH] Disable hardware DSP at boot time.
noefi [X86-32,X86-64] Disable EFI runtime services support.
noexec [IA-64]
@ -1381,13 +1418,15 @@ and is between 256 and 4096 characters. It is defined in the file
noexec32=off: disable non-executable mappings
read implies executable mappings
nofpu [SH] Disable hardware FPU at boot time.
nofxsr [BUGS=X86-32] Disables x86 floating point extended
register save and restore. The kernel will only save
legacy floating-point registers on task switch.
noclflush [BUGS=X86] Don't use the CLFLUSH instruction
nohlt [BUGS=ARM]
nohlt [BUGS=ARM,SH]
no-hlt [BUGS=X86-32] Tells the kernel that the hlt
instruction doesn't work correctly and not to
@ -1425,6 +1464,12 @@ and is between 256 and 4096 characters. It is defined in the file
nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
nox2apic [X86-64,APIC] Do not enable x2APIC mode.
x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
default x2apic cluster mode on platforms
supporting x2apic.
noltlbs [PPC] Do not use large page/tlb entries for kernel
lowmem mapping on PPC40x.
@ -1544,7 +1589,7 @@ and is between 256 and 4096 characters. It is defined in the file
See also Documentation/paride.txt.
pci=option[,option...] [PCI] various PCI subsystem options:
off [X86-32] don't probe for the PCI bus
off [X86] don't probe for the PCI bus
bios [X86-32] force use of PCI BIOS, don't access
the hardware directly. Use this if your machine
has a non-standard PCI host bridge.
@ -1552,9 +1597,9 @@ and is between 256 and 4096 characters. It is defined in the file
hardware access methods are allowed. Use this
if you experience crashes upon bootup and you
suspect they are caused by the BIOS.
conf1 [X86-32] Force use of PCI Configuration
conf1 [X86] Force use of PCI Configuration
Mechanism 1.
conf2 [X86-32] Force use of PCI Configuration
conf2 [X86] Force use of PCI Configuration
Mechanism 2.
noaer [PCIE] If the PCIEAER kernel config parameter is
enabled, this kernel boot option can be used to
@ -1574,37 +1619,37 @@ and is between 256 and 4096 characters. It is defined in the file
this option if the kernel is unable to allocate
IRQs or discover secondary PCI buses on your
motherboard.
rom [X86-32] Assign address space to expansion ROMs.
rom [X86] Assign address space to expansion ROMs.
Use with caution as certain devices share
address decoders between ROMs and other
resources.
norom [X86-32,X86_64] Do not assign address space to
norom [X86] Do not assign address space to
expansion ROMs that do not already have
BIOS assigned address ranges.
irqmask=0xMMMM [X86-32] Set a bit mask of IRQs allowed to be
irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
assigned automatically to PCI devices. You can
make the kernel exclude IRQs of your ISA cards
this way.
pirqaddr=0xAAAAA [X86-32] Specify the physical address
pirqaddr=0xAAAAA [X86] Specify the physical address
of the PIRQ table (normally generated
by the BIOS) if it is outside the
F0000h-100000h range.
lastbus=N [X86-32] Scan all buses thru bus #N. Can be
lastbus=N [X86] Scan all buses thru bus #N. Can be
useful if the kernel is unable to find your
secondary buses and you want to tell it
explicitly which ones they are.
assign-busses [X86-32] Always assign all PCI bus
assign-busses [X86] Always assign all PCI bus
numbers ourselves, overriding
whatever the firmware may have done.
usepirqmask [X86-32] Honor the possible IRQ mask stored
usepirqmask [X86] Honor the possible IRQ mask stored
in the BIOS $PIR table. This is needed on
some systems with broken BIOSes, notably
some HP Pavilion N5400 and Omnibook XE3
notebooks. This will have no effect if ACPI
IRQ routing is enabled.
noacpi [X86-32] Do not use ACPI for IRQ routing
noacpi [X86] Do not use ACPI for IRQ routing
or for PCI scanning.
use_crs [X86-32] Use _CRS for PCI resource
use_crs [X86] Use _CRS for PCI resource
allocation.
routeirq Do IRQ routing for all PCI devices.
This is normally done in pci_enable_device(),
@ -1633,6 +1678,12 @@ and is between 256 and 4096 characters. It is defined in the file
reserved for the CardBus bridge's memory
window. The default value is 64 megabytes.
pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
Management.
off Disable ASPM.
force Enable ASPM even on devices that claim not to support it.
WARNING: Forcing ASPM on may cause system lockups.
pcmv= [HW,PCMCIA] BadgePAD 4
pd. [PARIDE]
@ -1680,6 +1731,11 @@ and is between 256 and 4096 characters. It is defined in the file
autoconfiguration.
Ranges are in pairs (memory base and size).
dynamic_printk
Enables pr_debug()/dev_dbg() calls if
CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled. These can also
be switched on/off via <debugfs>/dynamic_printk/modules
print-fatal-signals=
[KNL] debug: print fatal signals
print-fatal-signals=1: print segfault info to
@ -1882,6 +1938,12 @@ and is between 256 and 4096 characters. It is defined in the file
shapers= [NET]
Maximal number of shapers.
show_msr= [x86] show boot-time MSR settings
Format: { <integer> }
Show boot-time (BIOS-initialized) MSR settings.
The parameter means the number of CPUs to show,
for example 1 means boot CPU only.
sim710= [SCSI,HW]
See header of drivers/scsi/sim710.c.
@ -2208,6 +2270,25 @@ and is between 256 and 4096 characters. It is defined in the file
autosuspended. Devices for which the delay is set
to a negative value won't be autosuspended at all.
usbcore.usbfs_snoop=
[USB] Set to log all usbfs traffic (default 0 = off).
usbcore.blinkenlights=
[USB] Set to cycle leds on hubs (default 0 = off).
usbcore.old_scheme_first=
[USB] Start with the old device initialization
scheme (default 0 = off).
usbcore.use_both_schemes=
[USB] Try the other device initialization scheme
if the first one fails (default 1 = enabled).
usbcore.initial_descriptor_timeout=
[USB] Specifies timeout for the initial 64-byte
USB_REQ_GET_DESCRIPTOR request in milliseconds
(default 5000 = 5.0 seconds).
usbhid.mousepoll=
[USBHID] The interval which mice are to be polled at.

4
Documentation/kobject.txt
View File

@ -118,6 +118,10 @@ the name of the kobject, call kobject_rename():
int kobject_rename(struct kobject *kobj, const char *new_name);
Note kobject_rename does perform any locking or have a solid notion of
what names are valid so the provide must provide their own sanity checking
and serialization.
There is a function called kobject_set_name() but that is legacy cruft and
is being removed. If your code needs to call this function, it is
incorrect and needs to be fixed.

149
Documentation/laptops/disk-shock-protection.txt Normal file
View File

@ -0,0 +1,149 @@
Hard disk shock protection
==========================
Author: Elias Oltmanns <eo@nebensachen.de>
Last modified: 2008-10-03
0. Contents
-----------
1. Intro
2. The interface
3. References
4. CREDITS
1. Intro
--------
ATA/ATAPI-7 specifies the IDLE IMMEDIATE command with unload feature.
Issuing this command should cause the drive to switch to idle mode and
unload disk heads. This feature is being used in modern laptops in
conjunction with accelerometers and appropriate software to implement
a shock protection facility. The idea is to stop all I/O operations on
the internal hard drive and park its heads on the ramp when critical
situations are anticipated. The desire to have such a feature
available on GNU/Linux systems has been the original motivation to
implement a generic disk head parking interface in the Linux kernel.
Please note, however, that other components have to be set up on your
system in order to get disk shock protection working (see
section 3. References below for pointers to more information about
that).
2. The interface
----------------
For each ATA device, the kernel exports the file
block/*/device/unload_heads in sysfs (here assumed to be mounted under
/sys). Access to /sys/block/*/device/unload_heads is denied with
-EOPNOTSUPP if the device does not support the unload feature.
Otherwise, writing an integer value to this file will take the heads
of the respective drive off the platter and block all I/O operations
for the specified number of milliseconds. When the timeout expires and
no further disk head park request has been issued in the meantime,
normal operation will be resumed. The maximal value accepted for a
timeout is 30000 milliseconds. Exceeding this limit will return
-EOVERFLOW, but heads will be parked anyway and the timeout will be
set to 30 seconds. However, you can always change a timeout to any
value between 0 and 30000 by issuing a subsequent head park request
before the timeout of the previous one has expired. In particular, the
total timeout can exceed 30 seconds and, more importantly, you can
cancel a previously set timeout and resume normal operation
immediately by specifying a timeout of 0. Values below -2 are rejected
with -EINVAL (see below for the special meaning of -1 and -2). If the
timeout specified for a recent head park request has not yet expired,
reading from /sys/block/*/device/unload_heads will report the number
of milliseconds remaining until normal operation will be resumed;
otherwise, reading the unload_heads attribute will return 0.
For example, do the following in order to park the heads of drive
/dev/sda and stop all I/O operations for five seconds:
# echo 5000 > /sys/block/sda/device/unload_heads
A simple
# cat /sys/block/sda/device/unload_heads
will show you how many milliseconds are left before normal operation
will be resumed.
A word of caution: The fact that the interface operates on a basis of
milliseconds may raise expectations that cannot be satisfied in
reality. In fact, the ATA specs clearly state that the time for an
unload operation to complete is vendor specific. The hint in ATA-7
that this will typically be within 500 milliseconds apparently has
been dropped in ATA-8.
There is a technical detail of this implementation that may cause some
confusion and should be discussed here. When a head park request has
been issued to a device successfully, all I/O operations on the
controller port this device is attached to will be deferred. That is
to say, any other device that may be connected to the same port will
be affected too. The only exception is that a subsequent head unload
request to that other device will be executed immediately. Further
operations on that port will be deferred until the timeout specified
for either device on the port has expired. As far as PATA (old style
IDE) configurations are concerned, there can only be two devices
attached to any single port. In SATA world we have port multipliers
which means that a user-issued head parking request to one device may
actually result in stopping I/O to a whole bunch of devices. However,
since this feature is supposed to be used on laptops and does not seem
to be very useful in any other environment, there will be mostly one
device per port. Even if the CD/DVD writer happens to be connected to
the same port as the hard drive, it generally *should* recover just
fine from the occasional buffer under-run incurred by a head park
request to the HD. Actually, when you are using an ide driver rather
than its libata counterpart (i.e. your disk is called /dev/hda
instead of /dev/sda), then parking the heads of one drive (drive X)
will generally not affect the mode of operation of another drive
(drive Y) on the same port as described above. It is only when a port
reset is required to recover from an exception on drive Y that further
I/O operations on that drive (and the reset itself) will be delayed
until drive X is no longer in the parked state.
Finally, there are some hard drives that only comply with an earlier
version of the ATA standard than ATA-7, but do support the unload
feature nonetheless. Unfortunately, there is no safe way Linux can
detect these devices, so you won't be able to write to the
unload_heads attribute. If you know that your device really does
support the unload feature (for instance, because the vendor of your
laptop or the hard drive itself told you so), then you can tell the
kernel to enable the usage of this feature for that drive by writing
the special value -1 to the unload_heads attribute:
# echo -1 > /sys/block/sda/device/unload_heads
will enable the feature for /dev/sda, and giving -2 instead of -1 will
disable it again.
3. References
-------------
There are several laptops from different vendors featuring shock
protection capabilities. As manufacturers have refused to support open
source development of the required software components so far, Linux
support for shock protection varies considerably between different
hardware implementations. Ideally, this section should contain a list
of pointers at different projects aiming at an implementation of shock
protection on different systems. Unfortunately, I only know of a
single project which, although still considered experimental, is fit
for use. Please feel free to add projects that have been the victims
of my ignorance.
- http://www.thinkwiki.org/wiki/HDAPS
See this page for information about Linux support of the hard disk
active protection system as implemented in IBM/Lenovo Thinkpads.
4. CREDITS
----------
This implementation of disk head parking has been inspired by a patch
originally published by Jon Escombe <lists@dresco.co.uk>. My efforts
to develop an implementation of this feature that is fit to be merged
into mainline have been aided by various kernel developers, in
particular by Tejun Heo and Bartlomiej Zolnierkiewicz.

10
Documentation/markers.txt
View File

@ -50,10 +50,12 @@ Connecting a function (probe) to a marker is done by providing a probe (function
to call) for the specific marker through marker_probe_register() and can be
activated by calling marker_arm(). Marker deactivation can be done by calling
marker_disarm() as many times as marker_arm() has been called. Removing a probe
is done through marker_probe_unregister(); it will disarm the probe and make
sure there is no caller left using the probe when it returns. Probe removal is
preempt-safe because preemption is disabled around the probe call. See the
"Probe example" section below for a sample probe module.
is done through marker_probe_unregister(); it will disarm the probe.
marker_synchronize_unregister() must be called before the end of the module exit
function to make sure there is no caller left using the probe. This, and the
fact that preemption is disabled around the probe call, make sure that probe
removal and module unload are safe. See the "Probe example" section below for a
sample probe module.
The marker mechanism supports inserting multiple instances of the same marker.
Markers can be put in inline functions, inlined static functions, and

714
Documentation/mtd/nand_ecc.txt Normal file
View File

@ -0,0 +1,714 @@
Introduction
============
Having looked at the linux mtd/nand driver and more specific at nand_ecc.c
I felt there was room for optimisation. I bashed the code for a few hours
performing tricks like table lookup removing superfluous code etc.
After that the speed was increased by 35-40%.
Still I was not too happy as I felt there was additional room for improvement.
Bad! I was hooked.
I decided to annotate my steps in this file. Perhaps it is useful to someone
or someone learns something from it.
The problem
===========
NAND flash (at least SLC one) typically has sectors of 256 bytes.
However NAND flash is not extremely reliable so some error detection
(and sometimes correction) is needed.
This is done by means of a Hamming code. I'll try to explain it in
laymans terms (and apologies to all the pro's in the field in case I do
not use the right terminology, my coding theory class was almost 30
years ago, and I must admit it was not one of my favourites).
As I said before the ecc calculation is performed on sectors of 256
bytes. This is done by calculating several parity bits over the rows and
columns. The parity used is even parity which means that the parity bit = 1
if the data over which the parity is calculated is 1 and the parity bit = 0
if the data over which the parity is calculated is 0. So the total
number of bits over the data over which the parity is calculated + the
parity bit is even. (see wikipedia if you can't follow this).
Parity is often calculated by means of an exclusive or operation,
sometimes also referred to as xor. In C the operator for xor is ^
Back to ecc.
Let's give a small figure:
byte 0: bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0 rp0 rp2 rp4 ... rp14
byte 1: bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0 rp1 rp2 rp4 ... rp14
byte 2: bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0 rp0 rp3 rp4 ... rp14
byte 3: bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0 rp1 rp3 rp4 ... rp14
byte 4: bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0 rp0 rp2 rp5 ... rp14
....
byte 254: bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0 rp0 rp3 rp5 ... rp15
byte 255: bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0 rp1 rp3 rp5 ... rp15
cp1 cp0 cp1 cp0 cp1 cp0 cp1 cp0
cp3 cp3 cp2 cp2 cp3 cp3 cp2 cp2
cp5 cp5 cp5 cp5 cp4 cp4 cp4 cp4
This figure represents a sector of 256 bytes.
cp is my abbreviaton for column parity, rp for row parity.
Let's start to explain column parity.
cp0 is the parity that belongs to all bit0, bit2, bit4, bit6.
so the sum of all bit0, bit2, bit4 and bit6 values + cp0 itself is even.
Similarly cp1 is the sum of all bit1, bit3, bit5 and bit7.
cp2 is the parity over bit0, bit1, bit4 and bit5
cp3 is the parity over bit2, bit3, bit6 and bit7.
cp4 is the parity over bit0, bit1, bit2 and bit3.
cp5 is the parity over bit4, bit5, bit6 and bit7.
Note that each of cp0 .. cp5 is exactly one bit.
Row parity actually works almost the same.
rp0 is the parity of all even bytes (0, 2, 4, 6, ... 252, 254)
rp1 is the parity of all odd bytes (1, 3, 5, 7, ..., 253, 255)
rp2 is the parity of all bytes 0, 1, 4, 5, 8, 9, ...
(so handle two bytes, then skip 2 bytes).
rp3 is covers the half rp2 does not cover (bytes 2, 3, 6, 7, 10, 11, ...)
for rp4 the rule is cover 4 bytes, skip 4 bytes, cover 4 bytes, skip 4 etc.
so rp4 calculates parity over bytes 0, 1, 2, 3, 8, 9, 10, 11, 16, ...)
and rp5 covers the other half, so bytes 4, 5, 6, 7, 12, 13, 14, 15, 20, ..
The story now becomes quite boring. I guess you get the idea.
rp6 covers 8 bytes then skips 8 etc
rp7 skips 8 bytes then covers 8 etc
rp8 covers 16 bytes then skips 16 etc
rp9 skips 16 bytes then covers 16 etc
rp10 covers 32 bytes then skips 32 etc
rp11 skips 32 bytes then covers 32 etc
rp12 covers 64 bytes then skips 64 etc
rp13 skips 64 bytes then covers 64 etc
rp14 covers 128 bytes then skips 128
rp15 skips 128 bytes then covers 128
In the end the parity bits are grouped together in three bytes as
follows:
ECC Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
ECC 0 rp07 rp06 rp05 rp04 rp03 rp02 rp01 rp00
ECC 1 rp15 rp14 rp13 rp12 rp11 rp10 rp09 rp08
ECC 2 cp5 cp4 cp3 cp2 cp1 cp0 1 1
I detected after writing this that ST application note AN1823
(http://www.st.com/stonline/books/pdf/docs/10123.pdf) gives a much
nicer picture.(but they use line parity as term where I use row parity)
Oh well, I'm graphically challenged, so suffer with me for a moment :-)
And I could not reuse the ST picture anyway for copyright reasons.
Attempt 0
=========
Implementing the parity calculation is pretty simple.
In C pseudocode:
for (i = 0; i < 256; i++)
{
if (i & 0x01)
rp1 = bit7 ^ bit6 ^ bit5 ^ bit4 ^ bit3 ^ bit2 ^ bit1 ^ bit0 ^ rp1;
else
rp0 = bit7 ^ bit6 ^ bit5 ^ bit4 ^ bit3 ^ bit2 ^ bit1 ^ bit0 ^ rp1;
if (i & 0x02)
rp3 = bit7 ^ bit6 ^ bit5 ^ bit4 ^ bit3 ^ bit2 ^ bit1 ^ bit0 ^ rp3;
else
rp2 = bit7 ^ bit6 ^ bit5 ^ bit4 ^ bit3 ^ bit2 ^ bit1 ^ bit0 ^ rp2;
if (i & 0x04)
rp5 = bit7 ^ bit6 ^ bit5 ^ bit4 ^ bit3 ^ bit2 ^ bit1 ^ bit0 ^ rp5;
else
rp4 = bit7 ^ bit6 ^ bit5 ^ bit4 ^ bit3 ^ bit2 ^ bit1 ^ bit0 ^ rp4;
if (i & 0x08)
rp7 = bit7 ^ bit6 ^ bit5 ^ bit4 ^ bit3 ^ bit2 ^ bit1 ^ bit0 ^ rp7;
else
rp6 = bit7 ^ bit6 ^ bit5 ^ bit4 ^ bit3 ^ bit2 ^ bit1 ^ bit0 ^ rp6;
if (i & 0x10)
rp9 = bit7 ^ bit6 ^ bit5 ^ bit4 ^ bit3 ^ bit2 ^ bit1 ^ bit0 ^ rp9;
else
rp8 = bit7 ^ bit6 ^ bit5 ^ bit4 ^ bit3 ^ bit2 ^ bit1 ^ bit0 ^ rp8;
if (i & 0x20)
rp11 = bit7 ^ bit6 ^ bit5 ^ bit4 ^ bit3 ^ bit2 ^ bit1 ^ bit0 ^ rp11;
else
rp10 = bit7 ^ bit6 ^ bit5 ^ bit4 ^ bit3 ^ bit2 ^ bit1 ^ bit0 ^ rp10;
if (i & 0x40)
rp13 = bit7 ^ bit6 ^ bit5 ^ bit4 ^ bit3 ^ bit2 ^ bit1 ^ bit0 ^ rp13;
else
rp12 = bit7 ^ bit6 ^ bit5 ^ bit4 ^ bit3 ^ bit2 ^ bit1 ^ bit0 ^ rp12;
if (i & 0x80)
rp15 = bit7 ^ bit6 ^ bit5 ^ bit4 ^ bit3 ^ bit2 ^ bit1 ^ bit0 ^ rp15;
else
rp14 = bit7 ^ bit6 ^ bit5 ^ bit4 ^ bit3 ^ bit2 ^ bit1 ^ bit0 ^ rp14;
cp0 = bit6 ^ bit4 ^ bit2 ^ bit0 ^ cp0;
cp1 = bit7 ^ bit5 ^ bit3 ^ bit1 ^ cp1;
cp2 = bit5 ^ bit4 ^ bit1 ^ bit0 ^ cp2;
cp3 = bit7 ^ bit6 ^ bit3 ^ bit2 ^ cp3
cp4 = bit3 ^ bit2 ^ bit1 ^ bit0 ^ cp4
cp5 = bit7 ^ bit6 ^ bit5 ^ bit4 ^ cp5
}
Analysis 0
==========
C does have bitwise operators but not really operators to do the above
efficiently (and most hardware has no such instructions either).
Therefore without implementing this it was clear that the code above was
not going to bring me a Nobel prize :-)
Fortunately the exclusive or operation is commutative, so we can combine
the values in any order. So instead of calculating all the bits
individually, let us try to rearrange things.
For the column parity this is easy. We can just xor the bytes and in the
end filter out the relevant bits. This is pretty nice as it will bring
all cp calculation out of the if loop.
Similarly we can first xor the bytes for the various rows.
This leads to:
Attempt 1
=========
const char parity[256] = {
0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0,
1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 1, 0, 1, 0, 0, 1,
1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 1, 0, 1, 0, 0, 1,
0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0,
1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 1, 0, 1, 0, 0, 1,
0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0,
0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0,
1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 1, 0, 1, 0, 0, 1,
1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 1, 0, 1, 0, 0, 1,
0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0,
0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0,
1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 1, 0, 1, 0, 0, 1,
0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0,
1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 1, 0, 1, 0, 0, 1,
1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 1, 0, 1, 0, 0, 1,
0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0
};
void ecc1(const unsigned char *buf, unsigned char *code)
{
int i;
const unsigned char *bp = buf;
unsigned char cur;
unsigned char rp0, rp1, rp2, rp3, rp4, rp5, rp6, rp7;
unsigned char rp8, rp9, rp10, rp11, rp12, rp13, rp14, rp15;
unsigned char par;
par = 0;
rp0 = 0; rp1 = 0; rp2 = 0; rp3 = 0;
rp4 = 0; rp5 = 0; rp6 = 0; rp7 = 0;
rp8 = 0; rp9 = 0; rp10 = 0; rp11 = 0;
rp12 = 0; rp13 = 0; rp14 = 0; rp15 = 0;
for (i = 0; i < 256; i++)
{
cur = *bp++;
par ^= cur;
if (i & 0x01) rp1 ^= cur; else rp0 ^= cur;
if (i & 0x02) rp3 ^= cur; else rp2 ^= cur;
if (i & 0x04) rp5 ^= cur; else rp4 ^= cur;
if (i & 0x08) rp7 ^= cur; else rp6 ^= cur;
if (i & 0x10) rp9 ^= cur; else rp8 ^= cur;
if (i & 0x20) rp11 ^= cur; else rp10 ^= cur;
if (i & 0x40) rp13 ^= cur; else rp12 ^= cur;
if (i & 0x80) rp15 ^= cur; else rp14 ^= cur;
}
code[0] =
(parity[rp7] << 7) |
(parity[rp6] << 6) |
(parity[rp5] << 5) |
(parity[rp4] << 4) |
(parity[rp3] << 3) |
(parity[rp2] << 2) |
(parity[rp1] << 1) |
(parity[rp0]);
code[1] =
(parity[rp15] << 7) |
(parity[rp14] << 6) |
(parity[rp13] << 5) |
(parity[rp12] << 4) |
(parity[rp11] << 3) |
(parity[rp10] << 2) |
(parity[rp9] << 1) |
(parity[rp8]);
code[2] =
(parity[par & 0xf0] << 7) |
(parity[par & 0x0f] << 6) |
(parity[par & 0xcc] << 5) |
(parity[par & 0x33] << 4) |
(parity[par & 0xaa] << 3) |
(parity[par & 0x55] << 2);
code[0] = ~code[0];
code[1] = ~code[1];
code[2] = ~code[2];
}
Still pretty straightforward. The last three invert statements are there to
give a checksum of 0xff 0xff 0xff for an empty flash. In an empty flash
all data is 0xff, so the checksum then matches.
I also introduced the parity lookup. I expected this to be the fastest
way to calculate the parity, but I will investigate alternatives later
on.
Analysis 1
==========
The code works, but is not terribly efficient. On my system it took
almost 4 times as much time as the linux driver code. But hey, if it was
*that* easy this would have been done long before.
No pain. no gain.
Fortunately there is plenty of room for improvement.
In step 1 we moved from bit-wise calculation to byte-wise calculation.
However in C we can also use the unsigned long data type and virtually
every modern microprocessor supports 32 bit operations, so why not try
to write our code in such a way that we process data in 32 bit chunks.
Of course this means some modification as the row parity is byte by
byte. A quick analysis:
for the column parity we use the par variable. When extending to 32 bits
we can in the end easily calculate p0 and p1 from it.
(because par now consists of 4 bytes, contributing to rp1, rp0, rp1, rp0
respectively)
also rp2 and rp3 can be easily retrieved from par as rp3 covers the
first two bytes and rp2 the last two bytes.
Note that of course now the loop is executed only 64 times (256/4).
And note that care must taken wrt byte ordering. The way bytes are
ordered in a long is machine dependent, and might affect us.
Anyway, if there is an issue: this code is developed on x86 (to be
precise: a DELL PC with a D920 Intel CPU)
And of course the performance might depend on alignment, but I expect
that the I/O buffers in the nand driver are aligned properly (and
otherwise that should be fixed to get maximum performance).
Let's give it a try...
Attempt 2
=========
extern const char parity[256];
void ecc2(const unsigned char *buf, unsigned char *code)
{
int i;
const unsigned long *bp = (unsigned long *)buf;
unsigned long cur;
unsigned long rp0, rp1, rp2, rp3, rp4, rp5, rp6, rp7;
unsigned long rp8, rp9, rp10, rp11, rp12, rp13, rp14, rp15;
unsigned long par;
par = 0;
rp0 = 0; rp1 = 0; rp2 = 0; rp3 = 0;
rp4 = 0; rp5 = 0; rp6 = 0; rp7 = 0;
rp8 = 0; rp9 = 0; rp10 = 0; rp11 = 0;
rp12 = 0; rp13 = 0; rp14 = 0; rp15 = 0;
for (i = 0; i < 64; i++)
{
cur = *bp++;
par ^= cur;
if (i & 0x01) rp5 ^= cur; else rp4 ^= cur;
if (i & 0x02) rp7 ^= cur; else rp6 ^= cur;
if (i & 0x04) rp9 ^= cur; else rp8 ^= cur;
if (i & 0x08) rp11 ^= cur; else rp10 ^= cur;
if (i & 0x10) rp13 ^= cur; else rp12 ^= cur;
if (i & 0x20) rp15 ^= cur; else rp14 ^= cur;
}
/*
we need to adapt the code generation for the fact that rp vars are now
long; also the column parity calculation needs to be changed.
we'll bring rp4 to 15 back to single byte entities by shifting and
xoring
*/
rp4 ^= (rp4 >> 16); rp4 ^= (rp4 >> 8); rp4 &= 0xff;
rp5 ^= (rp5 >> 16); rp5 ^= (rp5 >> 8); rp5 &= 0xff;
rp6 ^= (rp6 >> 16); rp6 ^= (rp6 >> 8); rp6 &= 0xff;
rp7 ^= (rp7 >> 16); rp7 ^= (rp7 >> 8); rp7 &= 0xff;
rp8 ^= (rp8 >> 16); rp8 ^= (rp8 >> 8); rp8 &= 0xff;
rp9 ^= (rp9 >> 16); rp9 ^= (rp9 >> 8); rp9 &= 0xff;
rp10 ^= (rp10 >> 16); rp10 ^= (rp10 >> 8); rp10 &= 0xff;
rp11 ^= (rp11 >> 16); rp11 ^= (rp11 >> 8); rp11 &= 0xff;
rp12 ^= (rp12 >> 16); rp12 ^= (rp12 >> 8); rp12 &= 0xff;
rp13 ^= (rp13 >> 16); rp13 ^= (rp13 >> 8); rp13 &= 0xff;
rp14 ^= (rp14 >> 16); rp14 ^= (rp14 >> 8); rp14 &= 0xff;
rp15 ^= (rp15 >> 16); rp15 ^= (rp15 >> 8); rp15 &= 0xff;
rp3 = (par >> 16); rp3 ^= (rp3 >> 8); rp3 &= 0xff;
rp2 = par & 0xffff; rp2 ^= (rp2 >> 8); rp2 &= 0xff;
par ^= (par >> 16);
rp1 = (par >> 8); rp1 &= 0xff;
rp0 = (par & 0xff);
par ^= (par >> 8); par &= 0xff;
code[0] =
(parity[rp7] << 7) |
(parity[rp6] << 6) |
(parity[rp5] << 5) |
(parity[rp4] << 4) |
(parity[rp3] << 3) |
(parity[rp2] << 2) |
(parity[rp1] << 1) |
(parity[rp0]);
code[1] =
(parity[rp15] << 7) |
(parity[rp14] << 6) |
(parity[rp13] << 5) |
(parity[rp12] << 4) |
(parity[rp11] << 3) |
(parity[rp10] << 2) |
(parity[rp9] << 1) |
(parity[rp8]);
code[2] =
(parity[par & 0xf0] << 7) |
(parity[par & 0x0f] << 6) |
(parity[par & 0xcc] << 5) |
(parity[par & 0x33] << 4) |
(parity[par & 0xaa] << 3) |
(parity[par & 0x55] << 2);
code[0] = ~code[0];
code[1] = ~code[1];
code[2] = ~code[2];
}
The parity array is not shown any more. Note also that for these
examples I kinda deviated from my regular programming style by allowing
multiple statements on a line, not using { } in then and else blocks
with only a single statement and by using operators like ^=
Analysis 2
==========
The code (of course) works, and hurray: we are a little bit faster than
the linux driver code (about 15%). But wait, don't cheer too quickly.
THere is more to be gained.
If we look at e.g. rp14 and rp15 we see that we either xor our data with
rp14 or with rp15. However we also have par which goes over all data.
This means there is no need to calculate rp14 as it can be calculated from
rp15 through rp14 = par ^ rp15;
(or if desired we can avoid calculating rp15 and calculate it from
rp14). That is why some places refer to inverse parity.
Of course the same thing holds for rp4/5, rp6/7, rp8/9, rp10/11 and rp12/13.
Effectively this means we can eliminate the else clause from the if
statements. Also we can optimise the calculation in the end a little bit
by going from long to byte first. Actually we can even avoid the table
lookups
Attempt 3
=========
Odd replaced:
if (i & 0x01) rp5 ^= cur; else rp4 ^= cur;
if (i & 0x02) rp7 ^= cur; else rp6 ^= cur;
if (i & 0x04) rp9 ^= cur; else rp8 ^= cur;
if (i & 0x08) rp11 ^= cur; else rp10 ^= cur;
if (i & 0x10) rp13 ^= cur; else rp12 ^= cur;
if (i & 0x20) rp15 ^= cur; else rp14 ^= cur;
with
if (i & 0x01) rp5 ^= cur;
if (i & 0x02) rp7 ^= cur;
if (i & 0x04) rp9 ^= cur;
if (i & 0x08) rp11 ^= cur;
if (i & 0x10) rp13 ^= cur;
if (i & 0x20) rp15 ^= cur;
and outside the loop added:
rp4 = par ^ rp5;
rp6 = par ^ rp7;
rp8 = par ^ rp9;
rp10 = par ^ rp11;
rp12 = par ^ rp13;
rp14 = par ^ rp15;
And after that the code takes about 30% more time, although the number of
statements is reduced. This is also reflected in the assembly code.
Analysis 3
==========
Very weird. Guess it has to do with caching or instruction parallellism
or so. I also tried on an eeePC (Celeron, clocked at 900 Mhz). Interesting
observation was that this one is only 30% slower (according to time)
executing the code as my 3Ghz D920 processor.
Well, it was expected not to be easy so maybe instead move to a
different track: let's move back to the code from attempt2 and do some
loop unrolling. This will eliminate a few if statements. I'll try
different amounts of unrolling to see what works best.
Attempt 4
=========
Unrolled the loop 1, 2, 3 and 4 times.
For 4 the code starts with:
for (i = 0; i < 4; i++)
{
cur = *bp++;
par ^= cur;
rp4 ^= cur;
rp6 ^= cur;
rp8 ^= cur;
rp10 ^= cur;
if (i & 0x1) rp13 ^= cur; else rp12 ^= cur;
if (i & 0x2) rp15 ^= cur; else rp14 ^= cur;
cur = *bp++;
par ^= cur;
rp5 ^= cur;
rp6 ^= cur;
...
Analysis 4
==========
Unrolling once gains about 15%
Unrolling twice keeps the gain at about 15%
Unrolling three times gives a gain of 30% compared to attempt 2.
Unrolling four times gives a marginal improvement compared to unrolling
three times.
I decided to proceed with a four time unrolled loop anyway. It was my gut
feeling that in the next steps I would obtain additional gain from it.
The next step was triggered by the fact that par contains the xor of all
bytes and rp4 and rp5 each contain the xor of half of the bytes.
So in effect par = rp4 ^ rp5. But as xor is commutative we can also say
that rp5 = par ^ rp4. So no need to keep both rp4 and rp5 around. We can
eliminate rp5 (or rp4, but I already foresaw another optimisation).
The same holds for rp6/7, rp8/9, rp10/11 rp12/13 and rp14/15.
Attempt 5
=========
Effectively so all odd digit rp assignments in the loop were removed.
This included the else clause of the if statements.
Of course after the loop we need to correct things by adding code like:
rp5 = par ^ rp4;
Also the initial assignments (rp5 = 0; etc) could be removed.
Along the line I also removed the initialisation of rp0/1/2/3.
Analysis 5
==========
Measurements showed this was a good move. The run-time roughly halved
compared with attempt 4 with 4 times unrolled, and we only require 1/3rd
of the processor time compared to the current code in the linux kernel.
However, still I thought there was more. I didn't like all the if
statements. Why not keep a running parity and only keep the last if
statement. Time for yet another version!
Attempt 6
=========
THe code within the for loop was changed to:
for (i = 0; i < 4; i++)
{
cur = *bp++; tmppar = cur; rp4 ^= cur;
cur = *bp++; tmppar ^= cur; rp6 ^= tmppar;
cur = *bp++; tmppar ^= cur; rp4 ^= cur;
cur = *bp++; tmppar ^= cur; rp8 ^= tmppar;
cur = *bp++; tmppar ^= cur; rp4 ^= cur; rp6 ^= cur;
cur = *bp++; tmppar ^= cur; rp6 ^= cur;
cur = *bp++; tmppar ^= cur; rp4 ^= cur;
cur = *bp++; tmppar ^= cur; rp10 ^= tmppar;
cur = *bp++; tmppar ^= cur; rp4 ^= cur; rp6 ^= cur; rp8 ^= cur;
cur = *bp++; tmppar ^= cur; rp6 ^= cur; rp8 ^= cur;
cur = *bp++; tmppar ^= cur; rp4 ^= cur; rp8 ^= cur;
cur = *bp++; tmppar ^= cur; rp8 ^= cur;
cur = *bp++; tmppar ^= cur; rp4 ^= cur; rp6 ^= cur;
cur = *bp++; tmppar ^= cur; rp6 ^= cur;
cur = *bp++; tmppar ^= cur; rp4 ^= cur;
cur = *bp++; tmppar ^= cur;
par ^= tmppar;
if ((i & 0x1) == 0) rp12 ^= tmppar;
if ((i & 0x2) == 0) rp14 ^= tmppar;
}
As you can see tmppar is used to accumulate the parity within a for
iteration. In the last 3 statements is is added to par and, if needed,
to rp12 and rp14.
While making the changes I also found that I could exploit that tmppar
contains the running parity for this iteration. So instead of having:
rp4 ^= cur; rp6 = cur;
I removed the rp6 = cur; statement and did rp6 ^= tmppar; on next
statement. A similar change was done for rp8 and rp10
Analysis 6
==========
Measuring this code again showed big gain. When executing the original
linux code 1 million times, this took about 1 second on my system.
(using time to measure the performance). After this iteration I was back
to 0.075 sec. Actually I had to decide to start measuring over 10
million interations in order not to loose too much accuracy. This one
definitely seemed to be the jackpot!
There is a little bit more room for improvement though. There are three
places with statements:
rp4 ^= cur; rp6 ^= cur;
It seems more efficient to also maintain a variable rp4_6 in the while
loop; This eliminates 3 statements per loop. Of course after the loop we
need to correct by adding:
rp4 ^= rp4_6;
rp6 ^= rp4_6
Furthermore there are 4 sequential assingments to rp8. This can be
encoded slightly more efficient by saving tmppar before those 4 lines
and later do rp8 = rp8 ^ tmppar ^ notrp8;
(where notrp8 is the value of rp8 before those 4 lines).
Again a use of the commutative property of xor.
Time for a new test!
Attempt 7
=========
The new code now looks like:
for (i = 0; i < 4; i++)
{
cur = *bp++; tmppar = cur; rp4 ^= cur;
cur = *bp++; tmppar ^= cur; rp6 ^= tmppar;
cur = *bp++; tmppar ^= cur; rp4 ^= cur;
cur = *bp++; tmppar ^= cur; rp8 ^= tmppar;
cur = *bp++; tmppar ^= cur; rp4_6 ^= cur;
cur = *bp++; tmppar ^= cur; rp6 ^= cur;
cur = *bp++; tmppar ^= cur; rp4 ^= cur;
cur = *bp++; tmppar ^= cur; rp10 ^= tmppar;
notrp8 = tmppar;
cur = *bp++; tmppar ^= cur; rp4_6 ^= cur;
cur = *bp++; tmppar ^= cur; rp6 ^= cur;
cur = *bp++; tmppar ^= cur; rp4 ^= cur;
cur = *bp++; tmppar ^= cur;
rp8 = rp8 ^ tmppar ^ notrp8;
cur = *bp++; tmppar ^= cur; rp4_6 ^= cur;
cur = *bp++; tmppar ^= cur; rp6 ^= cur;
cur = *bp++; tmppar ^= cur; rp4 ^= cur;
cur = *bp++; tmppar ^= cur;
par ^= tmppar;
if ((i & 0x1) == 0) rp12 ^= tmppar;
if ((i & 0x2) == 0) rp14 ^= tmppar;
}
rp4 ^= rp4_6;
rp6 ^= rp4_6;
Not a big change, but every penny counts :-)
Analysis 7
==========
Acutally this made things worse. Not very much, but I don't want to move
into the wrong direction. Maybe something to investigate later. Could
have to do with caching again.
Guess that is what there is to win within the loop. Maybe unrolling one
more time will help. I'll keep the optimisations from 7 for now.
Attempt 8
=========
Unrolled the loop one more time.
Analysis 8
==========
This makes things worse. Let's stick with attempt 6 and continue from there.
Although it seems that the code within the loop cannot be optimised
further there is still room to optimize the generation of the ecc codes.
We can simply calcualate the total parity. If this is 0 then rp4 = rp5
etc. If the parity is 1, then rp4 = !rp5;
But if rp4 = rp5 we do not need rp5 etc. We can just write the even bits
in the result byte and then do something like
code[0] |= (code[0] << 1);
Lets test this.
Attempt 9
=========
Changed the code but again this slightly degrades performance. Tried all
kind of other things, like having dedicated parity arrays to avoid the
shift after parity[rp7] << 7; No gain.
Change the lookup using the parity array by using shift operators (e.g.
replace parity[rp7] << 7 with:
rp7 ^= (rp7 << 4);
rp7 ^= (rp7 << 2);
rp7 ^= (rp7 << 1);
rp7 &= 0x80;
No gain.
The only marginal change was inverting the parity bits, so we can remove
the last three invert statements.
Ah well, pity this does not deliver more. Then again 10 million
iterations using the linux driver code takes between 13 and 13.5
seconds, whereas my code now takes about 0.73 seconds for those 10
million iterations. So basically I've improved the performance by a
factor 18 on my system. Not that bad. Of course on different hardware
you will get different results. No warranties!
But of course there is no such thing as a free lunch. The codesize almost
tripled (from 562 bytes to 1434 bytes). Then again, it is not that much.
Correcting errors
=================
For correcting errors I again used the ST application note as a starter,
but I also peeked at the existing code.
The algorithm itself is pretty straightforward. Just xor the given and
the calculated ecc. If all bytes are 0 there is no problem. If 11 bits
are 1 we have one correctable bit error. If there is 1 bit 1, we have an
error in the given ecc code.
It proved to be fastest to do some table lookups. Performance gain
introduced by this is about a factor 2 on my system when a repair had to
be done, and 1% or so if no repair had to be done.
Code size increased from 330 bytes to 686 bytes for this function.
(gcc 4.2, -O3)
Conclusion
==========
The gain when calculating the ecc is tremendous. Om my development hardware
a speedup of a factor of 18 for ecc calculation was achieved. On a test on an
embedded system with a MIPS core a factor 7 was obtained.
On a test with a Linksys NSLU2 (ARMv5TE processor) the speedup was a factor
5 (big endian mode, gcc 4.1.2, -O3)
For correction not much gain could be obtained (as bitflips are rare). Then
again there are also much less cycles spent there.
It seems there is not much more gain possible in this, at least when
programmed in C. Of course it might be possible to squeeze something more
out of it with an assembler program, but due to pipeline behaviour etc
this is very tricky (at least for intel hw).
Author: Frans Meulenbroeks
Copyright (C) 2008 Koninklijke Philips Electronics NV.

46
Documentation/networking/LICENSE.qlge Normal file
View File

@ -0,0 +1,46 @@
Copyright (c) 2003-2008 QLogic Corporation
QLogic Linux Networking HBA Driver
This program includes a device driver for Linux 2.6 that may be
distributed with QLogic hardware specific firmware binary file.
You may modify and redistribute the device driver code under the
GNU General Public License as published by the Free Software
Foundation (version 2 or a later version).
You may redistribute the hardware specific firmware binary file
under the following terms:
1. Redistribution of source code (only if applicable),
must retain the above copyright notice, this list of
conditions and the following disclaimer.
2. Redistribution in binary form must reproduce the above
copyright notice, this list of conditions and the
following disclaimer in the documentation and/or other
materials provided with the distribution.
3. The name of QLogic Corporation may not be used to
endorse or promote products derived from this software
without specific prior written permission
REGARDLESS OF WHAT LICENSING MECHANISM IS USED OR APPLICABLE,
THIS PROGRAM IS PROVIDED BY QLOGIC CORPORATION "AS IS'' AND ANY
EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR
BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
POSSIBILITY OF SUCH DAMAGE.
USER ACKNOWLEDGES AND AGREES THAT USE OF THIS PROGRAM WILL NOT
CREATE OR GIVE GROUNDS FOR A LICENSE BY IMPLICATION, ESTOPPEL, OR
OTHERWISE IN ANY INTELLECTUAL PROPERTY RIGHTS (PATENT, COPYRIGHT,
TRADE SECRET, MASK WORK, OR OTHER PROPRIETARY RIGHT) EMBODIED IN
ANY OTHER QLOGIC HARDWARE OR SOFTWARE EITHER SOLELY OR IN
COMBINATION WITH THIS PROGRAM.

44
Documentation/networking/can.txt
View File

@ -35,8 +35,9 @@ This file contains
6.1 general settings
6.2 local loopback of sent frames
6.3 CAN controller hardware filters
6.4 currently supported CAN hardware
6.5 todo
6.4 The virtual CAN driver (vcan)
6.5 currently supported CAN hardware
6.6 todo
7 Credits
@ -584,7 +585,42 @@ solution for a couple of reasons:
@133MHz with four SJA1000 CAN controllers from 2002 under heavy bus
load without any problems ...
6.4 currently supported CAN hardware (September 2007)
6.4 The virtual CAN driver (vcan)
Similar to the network loopback devices, vcan offers a virtual local
CAN interface. A full qualified address on CAN consists of
- a unique CAN Identifier (CAN ID)
- the CAN bus this CAN ID is transmitted on (e.g. can0)
so in common use cases more than one virtual CAN interface is needed.
The virtual CAN interfaces allow the transmission and reception of CAN
frames without real CAN controller hardware. Virtual CAN network
devices are usually named 'vcanX', like vcan0 vcan1 vcan2 ...
When compiled as a module the virtual CAN driver module is called vcan.ko
Since Linux Kernel version 2.6.24 the vcan driver supports the Kernel
netlink interface to create vcan network devices. The creation and
removal of vcan network devices can be managed with the ip(8) tool:
- Create a virtual CAN network interface:
ip link add type vcan
- Create a virtual CAN network interface with a specific name 'vcan42':
ip link add dev vcan42 type vcan
- Remove a (virtual CAN) network interface 'vcan42':
ip link del vcan42
The tool 'vcan' from the SocketCAN SVN repository on BerliOS is obsolete.
Virtual CAN network device creation in older Kernels:
In Linux Kernel versions < 2.6.24 the vcan driver creates 4 vcan
netdevices at module load time by default. This value can be changed
with the module parameter 'numdev'. E.g. 'modprobe vcan numdev=8'
6.5 currently supported CAN hardware
On the project website http://developer.berlios.de/projects/socketcan
there are different drivers available:
@ -603,7 +639,7 @@ solution for a couple of reasons:
Please check the Mailing Lists on the berlios OSS project website.
6.5 todo (September 2007)
6.6 todo
The configuration interface for CAN network drivers is still an open
issue that has not been finalized in the socketcan project. Also the

4
Documentation/networking/cs89x0.txt
View File

@ -3,7 +3,7 @@ NOTE
----
This document was contributed by Cirrus Logic for kernel 2.2.5. This version
has been updated for 2.3.48 by Andrew Morton <andrewm@uow.edu.au>
has been updated for 2.3.48 by Andrew Morton.
Cirrus make a copy of this driver available at their website, as
described below. In general, you should use the driver version which
@ -690,7 +690,7 @@ latest drivers and technical publications.
6.4 Current maintainer
In February 2000 the maintenance of this driver was assumed by Andrew
Morton <akpm@zip.com.au>
Morton.
6.5 Kernel module parameters

54
Documentation/networking/multiqueue.txt
View File

@ -24,4 +24,56 @@ netif_{start|stop|wake}_subqueue() functions to manage each queue while the
device is still operational. netdev->queue_lock is still used when the device
comes online or when it's completely shut down (unregister_netdev(), etc.).
Author: Peter P. Waskiewicz Jr. <peter.p.waskiewicz.jr@intel.com>
Section 2: Qdisc support for multiqueue devices
-----------------------------------------------
Currently two qdiscs are optimized for multiqueue devices. The first is the
default pfifo_fast qdisc. This qdisc supports one qdisc per hardware queue.
A new round-robin qdisc, sch_multiq also supports multiple hardware queues. The
qdisc is responsible for classifying the skb's and then directing the skb's to
bands and queues based on the value in skb->queue_mapping. Use this field in
the base driver to determine which queue to send the skb to.
sch_multiq has been added for hardware that wishes to avoid head-of-line
blocking. It will cycle though the bands and verify that the hardware queue
associated with the band is not stopped prior to dequeuing a packet.
On qdisc load, the number of bands is based on the number of queues on the
hardware. Once the association is made, any skb with skb->queue_mapping set,
will be queued to the band associated with the hardware queue.
Section 3: Brief howto using MULTIQ for multiqueue devices
---------------------------------------------------------------
The userspace command 'tc,' part of the iproute2 package, is used to configure
qdiscs. To add the MULTIQ qdisc to your network device, assuming the device
is called eth0, run the following command:
# tc qdisc add dev eth0 root handle 1: multiq
The qdisc will allocate the number of bands to equal the number of queues that
the device reports, and bring the qdisc online. Assuming eth0 has 4 Tx
queues, the band mapping would look like:
band 0 => queue 0
band 1 => queue 1
band 2 => queue 2
band 3 => queue 3
Traffic will begin flowing through each queue based on either the simple_tx_hash
function or based on netdev->select_queue() if you have it defined.
The behavior of tc filters remains the same. However a new tc action,
skbedit, has been added. Assuming you wanted to route all traffic to a
specific host, for example 192.168.0.3, through a specific queue you could use
this action and establish a filter such as:
tc filter add dev eth0 parent 1: protocol ip prio 1 u32 \
match ip dst 192.168.0.3 \
action skbedit queue_mapping 3
Author: Alexander Duyck <alexander.h.duyck@intel.com>
Original Author: Peter P. Waskiewicz Jr. <peter.p.waskiewicz.jr@intel.com>

175
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@ -0,0 +1,175 @@
Linux Phonet protocol family
============================
Introduction
------------
Phonet is a packet protocol used by Nokia cellular modems for both IPC
and RPC. With the Linux Phonet socket family, Linux host processes can
receive and send messages from/to the modem, or any other external
device attached to the modem. The modem takes care of routing.
Phonet packets can be exchanged through various hardware connections
depending on the device, such as:
- USB with the CDC Phonet interface,
- infrared,
- Bluetooth,
- an RS232 serial port (with a dedicated "FBUS" line discipline),
- the SSI bus with some TI OMAP processors.
Packets format
--------------
Phonet packets have a common header as follows:
struct phonethdr {
uint8_t pn_media; /* Media type (link-layer identifier) */
uint8_t pn_rdev; /* Receiver device ID */
uint8_t pn_sdev; /* Sender device ID */
uint8_t pn_res; /* Resource ID or function */
uint16_t pn_length; /* Big-endian message byte length (minus 6) */
uint8_t pn_robj; /* Receiver object ID */
uint8_t pn_sobj; /* Sender object ID */
};
On Linux, the link-layer header includes the pn_media byte (see below).
The next 7 bytes are part of the network-layer header.
The device ID is split: the 6 higher-order bits consitute the device
address, while the 2 lower-order bits are used for multiplexing, as are
the 8-bit object identifiers. As such, Phonet can be considered as a
network layer with 6 bits of address space and 10 bits for transport
protocol (much like port numbers in IP world).
The modem always has address number zero. All other device have a their
own 6-bit address.
Link layer
----------
Phonet links are always point-to-point links. The link layer header
consists of a single Phonet media type byte. It uniquely identifies the
link through which the packet is transmitted, from the modem's
perspective. Each Phonet network device shall prepend and set the media
type byte as appropriate. For convenience, a common phonet_header_ops
link-layer header operations structure is provided. It sets the
media type according to the network device hardware address.
Linux Phonet network interfaces support a dedicated link layer packets
type (ETH_P_PHONET) which is out of the Ethernet type range. They can
only send and receive Phonet packets.
The virtual TUN tunnel device driver can also be used for Phonet. This
requires IFF_TUN mode, _without_ the IFF_NO_PI flag. In this case,
there is no link-layer header, so there is no Phonet media type byte.
Note that Phonet interfaces are not allowed to re-order packets, so
only the (default) Linux FIFO qdisc should be used with them.
Network layer
-------------
The Phonet socket address family maps the Phonet packet header:
struct sockaddr_pn {
sa_family_t spn_family; /* AF_PHONET */
uint8_t spn_obj; /* Object ID */
uint8_t spn_dev; /* Device ID */
uint8_t spn_resource; /* Resource or function */
uint8_t spn_zero[...]; /* Padding */
};
The resource field is only used when sending and receiving;
It is ignored by bind() and getsockname().
Low-level datagram protocol
---------------------------
Applications can send Phonet messages using the Phonet datagram socket
protocol from the PF_PHONET family. Each socket is bound to one of the
2^10 object IDs available, and can send and receive packets with any
other peer.
struct sockaddr_pn addr = { .spn_family = AF_PHONET, };
ssize_t len;
socklen_t addrlen = sizeof(addr);
int fd;
fd = socket(PF_PHONET, SOCK_DGRAM, 0);
bind(fd, (struct sockaddr *)&addr, sizeof(addr));
/* ... */
sendto(fd, msg, msglen, 0, (struct sockaddr *)&addr, sizeof(addr));
len = recvfrom(fd, buf, sizeof(buf), 0,
(struct sockaddr *)&addr, &addrlen);
This protocol follows the SOCK_DGRAM connection-less semantics.
However, connect() and getpeername() are not supported, as they did
not seem useful with Phonet usages (could be added easily).
Phonet Pipe protocol
--------------------
The Phonet Pipe protocol is a simple sequenced packets protocol
with end-to-end congestion control. It uses the passive listening
socket paradigm. The listening socket is bound to an unique free object
ID. Each listening socket can handle up to 255 simultaneous
connections, one per accept()'d socket.
int lfd, cfd;
lfd = socket(PF_PHONET, SOCK_SEQPACKET, PN_PROTO_PIPE);
listen (lfd, INT_MAX);
/* ... */
cfd = accept(lfd, NULL, NULL);
for (;;)
{
char buf[...];
ssize_t len = read(cfd, buf, sizeof(buf));
/* ... */
write(cfd, msg, msglen);
}
Connections are established between two endpoints by a "third party"
application. This means that both endpoints are passive; so connect()
is not possible.
WARNING:
When polling a connected pipe socket for writability, there is an
intrinsic race condition whereby writability might be lost between the
polling and the writing system calls. In this case, the socket will
block until write becomes possible again, unless non-blocking mode
is enabled.
The pipe protocol provides two socket options at the SOL_PNPIPE level:
PNPIPE_ENCAP accepts one integer value (int) of:
PNPIPE_ENCAP_NONE: The socket operates normally (default).
PNPIPE_ENCAP_IP: The socket is used as a backend for a virtual IP
interface. This requires CAP_NET_ADMIN capability. GPRS data
support on Nokia modems can use this. Note that the socket cannot
be reliably poll()'d or read() from while in this mode.
PNPIPE_IFINDEX is a read-only integer value. It contains the
interface index of the network interface created by PNPIPE_ENCAP,
or zero if encapsulation is off.
Authors
-------
Linux Phonet was initially written by Sakari Ailus.
Other contributors include Mikä Liljeberg, Andras Domokos,
Carlos Chinea and Rémi Denis-Courmont.
Copyright (C) 2008 Nokia Corporation.

194
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@ -0,0 +1,194 @@
Linux wireless regulatory documentation
---------------------------------------
This document gives a brief review over how the Linux wireless
regulatory infrastructure works.
More up to date information can be obtained at the project's web page:
http://wireless.kernel.org/en/developers/Regulatory
Keeping regulatory domains in userspace
---------------------------------------
Due to the dynamic nature of regulatory domains we keep them
in userspace and provide a framework for userspace to upload
to the kernel one regulatory domain to be used as the central
core regulatory domain all wireless devices should adhere to.
How to get regulatory domains to the kernel
-------------------------------------------
Userspace gets a regulatory domain in the kernel by having
a userspace agent build it and send it via nl80211. Only
expected regulatory domains will be respected by the kernel.
A currently available userspace agent which can accomplish this
is CRDA - central regulatory domain agent. Its documented here:
http://wireless.kernel.org/en/developers/Regulatory/CRDA
Essentially the kernel will send a udev event when it knows
it needs a new regulatory domain. A udev rule can be put in place
to trigger crda to send the respective regulatory domain for a
specific ISO/IEC 3166 alpha2.
Below is an example udev rule which can be used:
# Example file, should be put in /etc/udev/rules.d/regulatory.rules
KERNEL=="regulatory*", ACTION=="change", SUBSYSTEM=="platform", RUN+="/sbin/crda"
The alpha2 is passed as an environment variable under the variable COUNTRY.
Who asks for regulatory domains?
--------------------------------
* Users
Users can use iw:
http://wireless.kernel.org/en/users/Documentation/iw
An example:
# set regulatory domain to "Costa Rica"
iw reg set CR
This will request the kernel to set the regulatory domain to
the specificied alpha2. The kernel in turn will then ask userspace
to provide a regulatory domain for the alpha2 specified by the user
by sending a uevent.
* Wireless subsystems for Country Information elements
The kernel will send a uevent to inform userspace a new
regulatory domain is required. More on this to be added
as its integration is added.
* Drivers
If drivers determine they need a specific regulatory domain
set they can inform the wireless core using regulatory_hint().
They have two options -- they either provide an alpha2 so that
crda can provide back a regulatory domain for that country or
they can build their own regulatory domain based on internal
custom knowledge so the wireless core can respect it.
*Most* drivers will rely on the first mechanism of providing a
regulatory hint with an alpha2. For these drivers there is an additional
check that can be used to ensure compliance based on custom EEPROM
regulatory data. This additional check can be used by drivers by
registering on its struct wiphy a reg_notifier() callback. This notifier
is called when the core's regulatory domain has been changed. The driver
can use this to review the changes made and also review who made them
(driver, user, country IE) and determine what to allow based on its
internal EEPROM data. Devices drivers wishing to be capable of world
roaming should use this callback. More on world roaming will be
added to this document when its support is enabled.
Device drivers who provide their own built regulatory domain
do not need a callback as the channels registered by them are
the only ones that will be allowed and therefore *additional*
cannels cannot be enabled.
Example code - drivers hinting an alpha2:
------------------------------------------
This example comes from the zd1211rw device driver. You can start
by having a mapping of your device's EEPROM country/regulatory
domain value to to a specific alpha2 as follows:
static struct zd_reg_alpha2_map reg_alpha2_map[] = {
{ ZD_REGDOMAIN_FCC, "US" },
{ ZD_REGDOMAIN_IC, "CA" },
{ ZD_REGDOMAIN_ETSI, "DE" }, /* Generic ETSI, use most restrictive */
{ ZD_REGDOMAIN_JAPAN, "JP" },
{ ZD_REGDOMAIN_JAPAN_ADD, "JP" },
{ ZD_REGDOMAIN_SPAIN, "ES" },
{ ZD_REGDOMAIN_FRANCE, "FR" },
Then you can define a routine to map your read EEPROM value to an alpha2,
as follows:
static int zd_reg2alpha2(u8 regdomain, char *alpha2)
{
unsigned int i;
struct zd_reg_alpha2_map *reg_map;
for (i = 0; i < ARRAY_SIZE(reg_alpha2_map); i++) {
reg_map = &reg_alpha2_map[i];
if (regdomain == reg_map->reg) {
alpha2[0] = reg_map->alpha2[0];
alpha2[1] = reg_map->alpha2[1];
return 0;
}
}
return 1;
}
Lastly, you can then hint to the core of your discovered alpha2, if a match
was found. You need to do this after you have registered your wiphy. You
are expected to do this during initialization.
r = zd_reg2alpha2(mac->regdomain, alpha2);
if (!r)
regulatory_hint(hw->wiphy, alpha2, NULL);
Example code - drivers providing a built in regulatory domain:
--------------------------------------------------------------
If you have regulatory information you can obtain from your
driver and you *need* to use this we let you build a regulatory domain
structure and pass it to the wireless core. To do this you should
kmalloc() a structure big enough to hold your regulatory domain
structure and you should then fill it with your data. Finally you simply
call regulatory_hint() with the regulatory domain structure in it.
Bellow is a simple example, with a regulatory domain cached using the stack.
Your implementation may vary (read EEPROM cache instead, for example).
Example cache of some regulatory domain
struct ieee80211_regdomain mydriver_jp_regdom = {
.n_reg_rules = 3,
.alpha2 = "JP",
//.alpha2 = "99", /* If I have no alpha2 to map it to */
.reg_rules = {
/* IEEE 802.11b/g, channels 1..14 */
REG_RULE(2412-20, 2484+20, 40, 6, 20, 0),
/* IEEE 802.11a, channels 34..48 */
REG_RULE(5170-20, 5240+20, 40, 6, 20,
NL80211_RRF_PASSIVE_SCAN),
/* IEEE 802.11a, channels 52..64 */
REG_RULE(5260-20, 5320+20, 40, 6, 20,
NL80211_RRF_NO_IBSS |
NL80211_RRF_DFS),
}
};
Then in some part of your code after your wiphy has been registered:
int r;
struct ieee80211_regdomain *rd;
int size_of_regd;
int num_rules = mydriver_jp_regdom.n_reg_rules;
unsigned int i;
size_of_regd = sizeof(struct ieee80211_regdomain) +
(num_rules * sizeof(struct ieee80211_reg_rule));
rd = kzalloc(size_of_regd, GFP_KERNEL);
if (!rd)
return -ENOMEM;
memcpy(rd, &mydriver_jp_regdom, sizeof(struct ieee80211_regdomain));
for (i=0; i < num_rules; i++) {
memcpy(&rd->reg_rules[i], &mydriver_jp_regdom.reg_rules[i],
sizeof(struct ieee80211_reg_rule));
}
r = regulatory_hint(hw->wiphy, NULL, rd);
if (r) {
kfree(rd);
return r;
}

85
Documentation/networking/tproxy.txt Normal file
View File

@ -0,0 +1,85 @@
Transparent proxy support
=========================
This feature adds Linux 2.2-like transparent proxy support to current kernels.
To use it, enable NETFILTER_TPROXY, the socket match and the TPROXY target in
your kernel config. You will need policy routing too, so be sure to enable that
as well.
1. Making non-local sockets work
================================
The idea is that you identify packets with destination address matching a local
socket on your box, set the packet mark to a certain value, and then match on that
value using policy routing to have those packets delivered locally:
# iptables -t mangle -N DIVERT
# iptables -t mangle -A PREROUTING -p tcp -m socket -j DIVERT
# iptables -t mangle -A DIVERT -j MARK --set-mark 1
# iptables -t mangle -A DIVERT -j ACCEPT
# ip rule add fwmark 1 lookup 100
# ip route add local 0.0.0.0/0 dev lo table 100
Because of certain restrictions in the IPv4 routing output code you'll have to
modify your application to allow it to send datagrams _from_ non-local IP
addresses. All you have to do is enable the (SOL_IP, IP_TRANSPARENT) socket
option before calling bind:
fd = socket(AF_INET, SOCK_STREAM, 0);
/* - 8< -*/
int value = 1;
setsockopt(fd, SOL_IP, IP_TRANSPARENT, &value, sizeof(value));
/* - 8< -*/
name.sin_family = AF_INET;
name.sin_port = htons(0xCAFE);
name.sin_addr.s_addr = htonl(0xDEADBEEF);
bind(fd, &name, sizeof(name));
A trivial patch for netcat is available here:
http://people.netfilter.org/hidden/tproxy/netcat-ip_transparent-support.patch
2. Redirecting traffic
======================
Transparent proxying often involves "intercepting" traffic on a router. This is
usually done with the iptables REDIRECT target; however, there are serious
limitations of that method. One of the major issues is that it actually
modifies the packets to change the destination address -- which might not be
acceptable in certain situations. (Think of proxying UDP for example: you won't
be able to find out the original destination address. Even in case of TCP
getting the original destination address is racy.)
The 'TPROXY' target provides similar functionality without relying on NAT. Simply
add rules like this to the iptables ruleset above:
# iptables -t mangle -A PREROUTING -p tcp --dport 80 -j TPROXY \
--tproxy-mark 0x1/0x1 --on-port 50080
Note that for this to work you'll have to modify the proxy to enable (SOL_IP,
IP_TRANSPARENT) for the listening socket.
3. Iptables extensions
======================
To use tproxy you'll need to have the 'socket' and 'TPROXY' modules
compiled for iptables. A patched version of iptables is available
here: http://git.balabit.hu/?p=bazsi/iptables-tproxy.git
4. Application support
======================
4.1. Squid
----------
Squid 3.HEAD has support built-in. To use it, pass
'--enable-linux-netfilter' to configure and set the 'tproxy' option on
the HTTP listener you redirect traffic to with the TPROXY iptables
target.
For more information please consult the following page on the Squid
wiki: http://wiki.squid-cache.org/Features/Tproxy4

9
Documentation/networking/vortex.txt
View File

@ -1,5 +1,5 @@
Documentation/networking/vortex.txt
Andrew Morton <andrewm@uow.edu.au>
Andrew Morton
30 April 2000
@ -11,7 +11,7 @@ The driver was written by Donald Becker <becker@scyld.com>
Don is no longer the prime maintainer of this version of the driver.
Please report problems to one or more of:
Andrew Morton <akpm@osdl.org>
Andrew Morton
Netdev mailing list <netdev@vger.kernel.org>
Linux kernel mailing list <linux-kernel@vger.kernel.org>
@ -305,11 +305,6 @@ Donald's wake-on-LAN page:
ftp://ftp.3com.com/pub/nic/3c90x/3c90xx2.exe
Driver updates and a detailed changelog for the modifications which
were made for the 2.3/2,4 series kernel is available at
http://www.zip.com.au/~akpm/linux/#3c59x-bc
Autonegotiation notes
---------------------

6
Documentation/pcmcia/driver-changes.txt
View File

@ -1,5 +1,11 @@
This file details changes in 2.6 which affect PCMCIA card driver authors:
* New configuration loop helper (as of 2.6.28)
By calling pcmcia_loop_config(), a driver can iterate over all available
configuration options. During a driver's probe() phase, one doesn't need
to use pcmcia_get_{first,next}_tuple, pcmcia_get_tuple_data and
pcmcia_parse_tuple directly in most if not all cases.
* New release helper (as of 2.6.17)
Instead of calling pcmcia_release_{configuration,io,irq,win}, all that's
necessary now is calling pcmcia_disable_device. As there is no valid

138
Documentation/power/regulator/machine.txt
View File

@ -2,17 +2,8 @@ Regulator Machine Driver Interface
===================================
The regulator machine driver interface is intended for board/machine specific
initialisation code to configure the regulator subsystem. Typical things that
machine drivers would do are :-
initialisation code to configure the regulator subsystem.
1. Regulator -> Device mapping.
2. Regulator supply configuration.
3. Power Domain constraint setting.
1. Regulator -> device mapping
==============================
Consider the following machine :-
Regulator-1 -+-> Regulator-2 --> [Consumer A @ 1.8 - 2.0V]
@ -21,81 +12,82 @@ Consider the following machine :-
The drivers for consumers A & B must be mapped to the correct regulator in
order to control their power supply. This mapping can be achieved in machine
initialisation code by calling :-
initialisation code by creating a struct regulator_consumer_supply for
each regulator.
int regulator_set_device_supply(const char *regulator, struct device *dev,
const char *supply);
struct regulator_consumer_supply {
struct device *dev; /* consumer */
const char *supply; /* consumer supply - e.g. "vcc" */
};
and is shown with the following code :-
e.g. for the machine above
regulator_set_device_supply("Regulator-1", devB, "Vcc");
regulator_set_device_supply("Regulator-2", devA, "Vcc");
static struct regulator_consumer_supply regulator1_consumers[] = {
{
.dev = &platform_consumerB_device.dev,
.supply = "Vcc",
},};
static struct regulator_consumer_supply regulator2_consumers[] = {
{
.dev = &platform_consumerA_device.dev,
.supply = "Vcc",
},};
This maps Regulator-1 to the 'Vcc' supply for Consumer B and maps Regulator-2
to the 'Vcc' supply for Consumer A.
Constraints can now be registered by defining a struct regulator_init_data
for each regulator power domain. This structure also maps the consumers
to their supply regulator :-
2. Regulator supply configuration.
==================================
Consider the following machine (again) :-
Regulator-1 -+-> Regulator-2 --> [Consumer A @ 1.8 - 2.0V]
|
+-> [Consumer B @ 3.3V]
static struct regulator_init_data regulator1_data = {
.constraints = {
.min_uV = 3300000,
.max_uV = 3300000,
.valid_modes_mask = REGULATOR_MODE_NORMAL,
},
.num_consumer_supplies = ARRAY_SIZE(regulator1_consumers),
.consumer_supplies = regulator1_consumers,
};
Regulator-1 supplies power to Regulator-2. This relationship must be registered
with the core so that Regulator-1 is also enabled when Consumer A enables it's
supply (Regulator-2).
supply (Regulator-2). The supply regulator is set by the supply_regulator_dev
field below:-
This relationship can be register with the core via :-
int regulator_set_supply(const char *regulator, const char *regulator_supply);
In this example we would use the following code :-
regulator_set_supply("Regulator-2", "Regulator-1");
Relationships can be queried by calling :-
const char *regulator_get_supply(const char *regulator);
3. Power Domain constraint setting.
===================================
Each power domain within a system has physical constraints on voltage and
current. This must be defined in software so that the power domain is always
operated within specifications.
Consider the following machine (again) :-
Regulator-1 -+-> Regulator-2 --> [Consumer A @ 1.8 - 2.0V]
|
+-> [Consumer B @ 3.3V]
This gives us two regulators and two power domains:
Domain 1: Regulator-2, Consumer B.
Domain 2: Consumer A.
Constraints can be registered by calling :-
int regulator_set_platform_constraints(const char *regulator,
struct regulation_constraints *constraints);
The example is defined as follows :-
struct regulation_constraints domain_1 = {
.min_uV = 3300000,
.max_uV = 3300000,
.valid_modes_mask = REGULATOR_MODE_NORMAL,
static struct regulator_init_data regulator2_data = {
.supply_regulator_dev = &platform_regulator1_device.dev,
.constraints = {
.min_uV = 1800000,
.max_uV = 2000000,
.valid_ops_mask = REGULATOR_CHANGE_VOLTAGE,
.valid_modes_mask = REGULATOR_MODE_NORMAL,
},
.num_consumer_supplies = ARRAY_SIZE(regulator2_consumers),
.consumer_supplies = regulator2_consumers,
};
struct regulation_constraints domain_2 = {
.min_uV = 1800000,
.max_uV = 2000000,
.valid_ops_mask = REGULATOR_CHANGE_VOLTAGE,
.valid_modes_mask = REGULATOR_MODE_NORMAL,
};
Finally the regulator devices must be registered in the usual manner.
regulator_set_platform_constraints("Regulator-1", &domain_1);
regulator_set_platform_constraints("Regulator-2", &domain_2);
static struct platform_device regulator_devices[] = {
{
.name = "regulator",
.id = DCDC_1,
.dev = {
.platform_data = &regulator1_data,
},
},
{
.name = "regulator",
.id = DCDC_2,
.dev = {
.platform_data = &regulator2_data,
},
},
};
/* register regulator 1 device */
platform_device_register(&wm8350_regulator_devices[0]);
/* register regulator 2 device */
platform_device_register(&wm8350_regulator_devices[1]);

8
Documentation/power/regulator/regulator.txt
View File

@ -10,11 +10,11 @@ Registration
Drivers can register a regulator by calling :-
struct regulator_dev *regulator_register(struct regulator_desc *regulator_desc,
void *reg_data);
struct regulator_dev *regulator_register(struct device *dev,
struct regulator_desc *regulator_desc);
This will register the regulators capabilities and operations the regulator
core. The core does not touch reg_data (private to regulator driver).
This will register the regulators capabilities and operations to the regulator
core.
Regulators can be unregistered by calling :-

18
Documentation/power/s2ram.txt
View File

@ -54,3 +54,21 @@ used to run with "radeonfb" (it's an ATI Radeon mobility). It turns out
that "radeonfb" simply cannot resume that device - it tries to set the
PLL's, and it just _hangs_. Using the regular VGA console and letting X
resume it instead works fine.
NOTE
====
pm_trace uses the system's Real Time Clock (RTC) to save the magic number.
Reason for this is that the RTC is the only reliably available piece of
hardware during resume operations where a value can be set that will
survive a reboot.
Consequence is that after a resume (even if it is successful) your system
clock will have a value corresponding to the magic mumber instead of the
correct date/time! It is therefore advisable to use a program like ntp-date
or rdate to reset the correct date/time from an external time source when
using this trace option.
As the clock keeps ticking it is also essential that the reboot is done
quickly after the resume failure. The trace option does not use the seconds
or the low order bits of the minutes of the RTC, but a too long delay will
corrupt the magic value.

4
Documentation/powerpc/00-INDEX
View File

@ -18,10 +18,6 @@ mpc52xx.txt
- Linux 2.6.x on MPC52xx family
mpc52xx-device-tree-bindings.txt
- MPC5200 Device Tree Bindings
ppc_htab.txt
- info about the Linux/PPC /proc/ppc_htab entry
smp.txt
- use and state info about Linux/PPC on MP machines
sound.txt
- info on sound support under Linux/PPC
zImage_layout.txt

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