This patch creates platform_device entries for the Marvell mv64x60
MPSC (multi-protocol serial controller) ports, based on information
contained in the device tree.
This driver (like the other mv64x60 drivers) are unusual in that it
works on both the MIPS and PowerPC architectures. Because of that,
the drivers do not support the normal PowerPC of_platform_bus_type.
They support platform_bus_type instead.
Signed-off-by: Dale Farnsworth <dale@farnsworth.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Paul Mackerras <paulus@samba.org>
There are 3 interrupt groups each with its own status/mask registers.
We use a separate struct irq_chip for each interrupt group and handle
interrupts in two stages or levels: level 1 selects the appropriate
struct irq_chip, and level 2 selects individual interrupts within
that irq_chip.
Signed-off-by: Dale Farnsworth <dale@farnsworth.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>
Some platforms support a variety processor modules with no method of
determining which exact processor module is being used except by
examining Vital Product Data (VPD). The modules may have different
amounts of memory, clock frequencies, etc. so reading the VPD becomes
necessary to correctly set properties in the device tree before its
passed to the kernel.
Often the VPD is stored in I2C EEPROMs so an I2C driver becomes necessary.
This I2C driver is for the I2C controller that's embedded on the Marvel
mv64x60 line of host bridges.
Signed-off-by: Mark A. Greer <mgreer@mvista.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>
The bootwrapper requires a serial driver to allow cmdline editing
and information reporting on the console. This driver is required
by platforms that boot a zImage and use the MPSC for the console.
Signed-off-by: Mark A. Greer <mgreer@mvista.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>
The mv64x60 host bridge has many windows between its various components
(cpu, system memory, ethernet ctlr, MPSC, DMA ctlr, PCI MEM, PCI I/O).
Unfortunately, the firmware on some of mv64x60-based platforms do not
properly or completely configure those windows (e.g., MPSC->system memory
windows not configured or CPU->PCI MEM space not configured).
So, the missing configuration needs to be done in either the bootwrapper
or in the kernel. To keep the kernel as clean as possible, it is done
in the bootwrapper. Note that I/O controller configuration is NOT being
done, its only the windows to allow the I/O controllers and other components
to access memory, etc. that is being done--drivers assume that their
controllers can already access system memory).
Table of routines and the windows they configure:
mv64x60_config_ctlr_windows() ENET->System Memory
MPSC->System Memory
IDMA->System Memory
mv64x60_config_pci_windows() PCI MEM->System Memory
PCI I/O->Bridge's Registers
mv64x60_config_cpu2pci_window() CPU->PCI MEM
CPU->PCI I/O
Signed-off-by: Mark A. Greer <mgreer@mvista.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>
Add 'zImage.dts' and 'zImage.dts_initrd' build rules that automatically
compile and wrap a dts file from arch/powerpc/boot/dts into the zImage file.
The resulting zImage will be arch/powerpc/boot/zImage.dts.<platform> and
arch/powerpc/boot/zImage.dts_initrd.<platform>, respectively.
Having separate rules allows the user to choose whether to include a device
tree--and which device tree--at build time. This is useful when one Makefile
target builds a zImage that runs on several platforms except for differing
device trees. By just setting CONFIG_DEVICE_TREE and running "make zImage.dts"
the exact zImage you want is built without Makefile bloat or manually running
the wrapper script.
The dts file is expected to be arch/powerpc/boot/dts/$(CONFIG_DEVICE_TREE)
Signed-off-by: Mark A. Greer <mgreer@mvista.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>
The boot wrapper platform init code on 83xx and 85xx using the cuboot
platform type was incorrectly assuming that u-boot supplied the size
of the initrd, whereas it actually supplies the end address. This
fixes it.
Signed-off-by: Scott Wood <scottwood@freescale.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>
An mdio bus scan was added with ucc_geth phylib
migration patches, now machines complain on boot, saying:
prom_parse: Bad cell count for /qe@e0100000/mdio@2120/ethernet-phy@00
prom_parse: Bad cell count for /qe@e0100000/mdio@2120/ethernet-phy@01
since size-cells can indeed be 0, this patch fixes the check.
Signed-off-by: Kim Phillips <kim.phillips@freescale.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>
Greatly simplify the function smp_space_timers.
The stolen time calculation (per comment within the code) doesn't need the
half-jiffy stagger any more. There isn't an issue with bouncing off global
locks, so we really shouldn't need any sort of staggering at all.
However, the last_jiffy value still needs to be set. This removes the
extra stagger logic, and just sets the values.
This change should benefit applications that rely on barrier
synchronization, and will help cut down OS jitter.
Boot tested across the board (G5,power3,power4,power5,970mp blade).
Signed-off-by: Will Schmidt <will_schmidt@vnet.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>
Fixes warnings:
arch/powerpc/platforms/ps3/system-bus.c: In function 'ps3_map_sg':
arch/powerpc/platforms/ps3/system-bus.c:278: warning: unused variable 'i'
arch/powerpc/platforms/ps3/system-bus.c:277: warning: unused variable 'dev'
arch/powerpc/platforms/ps3/setup.c:103: warning: 'prealloc' defined but not used
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Acked-by: Geoff Levand <geoffrey.levand@am.sony.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>
fixes:
arch/powerpc/platforms/pasemi/idle.c: In function 'pasemi_system_reset_exception':
arch/powerpc/platforms/pasemi/idle.c:55: warning: implicit declaration of function 'do_IRQ'
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Paul Mackerras <paulus@samba.org>
This case will never be hit, but it should be corrected anyway.
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Paul Mackerras <paulus@samba.org>
* 'linus' of master.kernel.org:/pub/scm/linux/kernel/git/perex/alsa: (122 commits)
[ALSA] version 1.0.14rc4
[ALSA] Add speaker pin sequencing to hda_codec.c:snd_hda_parse_pin_def_config()
[ALSA] hda-codec - Add ALC861VD Lenovo support
[ALSA] hda-codec - Fix connection list in generic parser
[ALSA] usb-audio: work around wrong wMaxPacketSize on ESI M4U
[ALSA] usb-audio: work around broken M-Audio MidiSport Uno firmware
[ALSA] usb-audio: explicitly match Logitech QuickCam
[ALSA] hda-codec - Fix a typo
[ALSA] hda-codec - Fix ALC880 uniwill auto-mutes
[ALSA] hda-codec - Fix AD1988 SPDIF playback route control
[ALSA] wm8750 typo fix
[ALSA] wavefront: only declare isapnp on CONFIG_PNP
[ALSA] hda-codec - bug fixes for stac92xx HDA codecs.
[ALSA] add MODULE_FIRMWARE entries
[ALSA] do not depend on FW_LOADER when internal firmware images are used
[ALSA] hda-codec - Fix resume of STAC92xx codecs
[ALSA] usbaudio - Revert the minimal period size fix patch
[ALSA] hda-codec - Add support for new HP DV series laptops
[ALSA] usb-audio - Fix the minimum period size per transfer mode
[ALSA] sound/pcmcia/vx/vxpocket.c: fix an if() condition
...
* 'master' of ssh://master.kernel.org/pub/scm/linux/kernel/git/mchehab/v4l-dvb: (44 commits)
V4L/DVB (5571): V4l1-compat: Make VIDIOCSPICT return errors in a useful way
V4L/DVB (5624): Radio-maestro.c cleanup
V4L/DVB (5623): Dsbr100.c Replace usb_dsbr100_do_ioctl to use video_ioctl2
V4L/DVB (5622): Radio-zoltrix.c cleanup
V4L/DVB (5621): Radio-cadet.c Replace cadet_do_ioctl to use video_ioctl2
V4L/DVB (5619): Dvb-usb: fix typo
V4L/DVB (5618): Cx88: Drop the generic i2c client from cx88-vp3054-i2c
V4L/DVB (5617): V4L2: videodev, allow debugging
V4L/DVB (5614): M920x: Disable second adapter on LifeView TV Walker Twin
V4L/DVB (5613): M920x: loosen up 80-col limit
V4L/DVB (5612): M920x: rename function prefixes from m9206_foo to m920x_foo
V4L/DVB (5611): M920x: replace deb_rc with deb
V4L/DVB (5610): M920x: remove duplicated code
V4L/DVB (5609): M920x: group like functions together
V4L/DVB (5608): M920x: various whitespace cleanups
V4L/DVB (5607): M920x: Initial support for devices likely manufactured by Dposh
V4L/DVB (5606): M920x: add "c-basic-offset: 8" to help emacs to enforce tabbing
V4L/DVB (5605): M920x: Add support for LifeView TV Walker Twin
V4L/DVB (5603): V4L: Prevent queueing queued buffers.
V4L/DVB (5602): Enable DiSEqC in Starbox II (vp7021a)
...
* 'release' of git://git.kernel.org/pub/scm/linux/kernel/git/aegl/linux-2.6:
[IA64] Quicklist support for IA64
[IA64] fix Kprobes reentrancy
[IA64] SN: validate smp_affinity mask on intr redirect
[IA64] drivers/char/snsc_event.c:206: warning: unused variable `p'
[IA64] mca.c:121: warning: 'cpe_poll_timer' defined but not used
[IA64] Fix - Section mismatch: reference to .init.data:mvec_name
[IA64] more warning cleanups
[IA64] Wire up epoll_pwait and utimensat
[IA64] Fix warnings resulting from type-checking in dev_dbg()
[IA64] typo s/kenrel/kernel/
The code was ok, but triggered warnings for calling __init from
__cpuinit. Instead call it from check_bugs instead.
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
I'm using a custom BIOS to configure the northbridge GART at address
0x80000000, size 2G. Linux complains:
"Aperture from northbridge cpu 0 beyond 4GB. Ignoring."
I think there's an off-by-two error in arch/x86_64/kernel/aperture.c:
AK: use correct types for i386
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* git://git.kernel.org/pub/scm/linux/kernel/git/bunk/trivial:
further UTF-8 fixes and name correction
Fix wrong identifier name in Documentation/kref.txt
> -** Copyright 1994 by Bj<94>rn Brauel
> +** Copyright 1994 by Bj”rn Brauel
I think these were cp437, and it should read 'Björn'.
(asm-m68k/atari*.h)
Also note that Arnaldo just put more legacy noise into CREDITS...
Signed-off-by: Adrian Bunk <bunk@stusta.de>
There's a typo / wrong identifier name in Documentation/kref.txt. Fix it.
Signed-off-by: Satyam Sharma <ssatyam@cse.iitk.ac.in>
Acked-by: Corey Minyard <minyard@acm.org>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
* 'upstream' of git://ftp.linux-mips.org/pub/scm/upstream-linus: (28 commits)
[MIPS] Rework cobalt_board_id
[MIPS] Use RTC_CMOS for Cobalt
[MIPS] Use platform_device for Cobalt UART
[MIPS] Separate Alchemy processor based boards config
[MIPS] Fix build error in atomic64_cmpxchg
[MIPS] Run checksyscalls for N32 and O32 ABI
[MIPS] tlbex: use __maybe_unused
[MIPS] excite: use __maybe_unused
[MIPS] Add extern cobalt_board_id
[MIPS] Remove unused CONFIG_TOSHIBA_BOARDS
[MIPS] Rename tb0229_defconfig to tb0219_defconfig
[MIPS] Update tb0229_defconfig; add CONFIG_GPIO_TB0219.
[MIPS] Add minimum defconfig for RBHMA4200
[MIPS] SB1: Build fix.
[MIPS] Drop __devinit tag from allocate_irqno() and free_irqno()
[MIPS] clocksource: use CLOCKSOURCE_MASK() macro
[MIPS] Remove LIMITED_DMA support
[MIPS] Remove Momenco Jaguar ATX support
[MIPS] Remove Momenco Ocelot G support
[MIPS] FPU hazard handling
...
* 'for-linus' of git://git.kernel.dk/data/git/linux-2.6-block:
Fix compile/link of init/do_mounts.c with !CONFIG_BLOCK
When stacked block devices are in-use (e.g. md or dm), the recursive calls
* 'audit.b38' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/audit-current:
[PATCH] Abnormal End of Processes
[PATCH] match audit name data
[PATCH] complete message queue auditing
[PATCH] audit inode for all xattr syscalls
[PATCH] initialize name osid
[PATCH] audit signal recipients
[PATCH] add SIGNAL syscall class (v3)
[PATCH] auditing ptrace
* 'upstream-fixes' of master.kernel.org:/pub/scm/linux/kernel/git/jikos/hid:
USB HID: hiddev - fix race between hiddev_send_event() and hiddev_release()
HID: add hooks for getkeycode() and setkeycode() methods
HID: switch to using input_dev->dev.parent
USB HID: Logitech wheel 0x046d/0xc294 needs HID_QUIRK_NOGET quirk
USB HID: usb_buffer_free() cleanup
USB HID: report descriptor of Cypress USB barcode readers needs fixup
Bluetooth HID: HIDP - don't initialize force feedback
USB HID: update CONFIG_USB_HIDINPUT_POWERBOOK description
HID: add input mappings for non-working keys on Logitech S510 remote
IA64 is the origin of the quicklist implementation. So cut out the pieces
that are now in core code and modify the functions called.
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Tony Luck <tony.luck@intel.com>
In case of reentrance i.e when a probe handler calls a functions which
inturn has a probe, we save a previous kprobe information and just single
step the reentrant probe without calling the actual probe handler. During
this reentracy period, if an interrupt occurs and if probe happens to
trigger in the inturrupt path, then we were corrupting the previous kprobe(
as we were overriding the previous kprobe info) info their by crashing the
system. This patch fixes this issues by having a an array of previous
kprobe info struct(with the array size of 2).
This similar technique is not needed on i386 and x86_64 because by default
interrupts are turn off in the break/int3 exception handler.
Signed-off-by: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Tony Luck <tony.luck@intel.com>
On SN, only allow one bit to be set in the smp_affinty mask when
redirecting an interrupt. Currently setting multiple bits is allowed, but
only the first bit is used in determining the CPU to redirect to. This has
caused confusion among some customers.
[akpm@linux-foundation.org: fixes]
Signed-off-by: John Keller <jpk@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Tony Luck <tony.luck@intel.com>
* master.kernel.org:/pub/scm/linux/kernel/git/davem/net-2.6: (31 commits)
[NETFILTER]: xt_conntrack: add compat support
[NETFILTER]: iptable_raw: ignore short packets sent by SOCK_RAW sockets
[NETFILTER]: iptable_{filter,mangle}: more descriptive "happy cracking" message
[NETFILTER]: nf_nat: Clears helper private area when NATing
[NETFILTER]: ctnetlink: clear helper area and handle unchanged helper
[NETFILTER]: nf_conntrack: Removes unused destroy operation of l3proto
[NETFILTER]: nf_conntrack: Removes duplicated declarations
[NETFILTER]: nf_nat: remove unused argument of function allocating binding
[NETFILTER]: Clean up table initialization
[NET_SCHED]: Avoid requeue warning on dev_deactivate
[NET_SCHED]: Reread dev->qdisc for NETDEV_TX_OK
[NET_SCHED]: Rationalise return value of qdisc_restart
[NET]: Fix dev->qdisc race for NETDEV_TX_LOCKED case
[UDP]: Fix AF-specific references in AF-agnostic code.
[IrDA]: KingSun/DonShine USB IrDA dongle support.
[IPV6] ROUTE: Assign rt6i_idev for ip6_{prohibit,blk_hole}_entry.
[IPV6]: Do no rely on skb->dst before it is assigned.
[IPV6]: Send ICMPv6 error on scope violations.
[SCTP]: Do not include ABORT chunk header in the notification.
[SCTP]: Correctly copy addresses in sctp_copy_laddrs
...
When exporting input device bitmaps via compat_ioctl on BIG_ENDIAN
platforms evdev calculates data size incorrectly. This causes buffer
overflow if user specifies buffer smaller than maxlen.
Signed-off-by: Kenichi Nagai <kenichi3.nagai@toshiba.co.jp>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
During a 'resync' or similar activity, md checks if the devices in the
array are otherwise active and winds back resync activity when they are.
This test in done in is_mddev_idle, and it is somewhat fragile - it
sometimes thinks there is non-sync io when there isn't.
The test compares the total sectors of io (disk_stat_read) with the sectors
of resync io (disk->sync_io). This has problems because total sectors gets
updated when a request completes, while resync io gets updated when the
request is submitted. The time difference can cause large differenced
between the two which do not actually imply non-resync activity. The test
currently allows for some fuzz (+/- 4096) but there are some cases when it
is not enough.
The test currently looks for any (non-fuzz) difference, either positive or
negative. This clearly is not needed. Any non-sync activity will cause
the total sectors to grow faster than the sync_io count (never slower) so
we only need to look for a positive differences.
If we do this then the amount of in-flight sync io will never cause the
appearance of non-sync IO. Once enough non-sync IO to worry about starts
happening, resync will be slowed down and the measurements will thus be
more precise (as there is less in-flight) and control of resync will still
be suitably responsive.
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Remove the obsolete "if [ ]" construct from the video console Kconfig
file.
Signed-off-by: Robert P. J. Day <rpjday@mindspring.com>
Acked-by: James Simmons <jsimmons@infradead.org>
Cc: "Antonino A. Daplas" <adaplas@pol.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Convert internal wait_pm2() function to fb API fb_sync() method.
Signed-off-by: Krzysztof Helt <krzysztof.h1@wp.pl>
Signed-off-by: Antonino Daplas <adaplas@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Let the user enable debugging messages in nvidiafb.
Signed-off-by: Jean Delvare <khali@linux-fr.org>
Signed-off-by: Antonino Daplas <adaplas@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Adds a framebuffer driver to ATMEL AT91SAM9x and AT32 aka AVR32 platforms.
Those chips share quite the same IP and this code is suitable for both
architectures.
Signed-off-by: Nicolas Ferre <nicolas.ferre@rfo.atmel.com>
Signed-off-by: Antonino Daplas <adaplas@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This is a basic port from 2.4 kernel to 2.6. Acceleration is lost and big
endian support probably too. The driver works in 8, 16 and 32 bit mode.
[adaplas]
- change VESA_* to FB_BLANK_* constants
- removed unused function clear_memory
- fix uninitialized variable compiler warning
- some whitespace cleaning
[akpm@linux-foundation.org: Nuke pestiferous CVS string]
Signed-off-by: Krzysztof Helt <krzysztof.h1@wp.pl>
Signed-off-by: Antonino Daplas <adaplas@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Re-arrange epoll code to avoid static functions pre-declarations, and apply
akpm-filter on it.
Signed-off-by: Davide Libenzi <davidel@xmailserver.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Epoll is either compiled it, or not (if EMBEDDED). Remove the module code
and use fs_initcall().
Signed-off-by: Davide Libenzi <davidel@xmailserver.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Cut out lots of code from epoll, by reusing the anonymous inode source
patch (fs/anon_inodes.c).
Signed-off-by: Davide Libenzi <davidel@xmailserver.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This is an example about how to add eventfd support to the current KAIO code,
in order to enable KAIO to post readiness events to a pollable fd (hence
compatible with POSIX select/poll). The KAIO code simply signals the eventfd
fd when events are ready, and this triggers a POLLIN in the fd. This patch
uses a reserved for future use member of the struct iocb to pass an eventfd
file descriptor, that KAIO will use to post events every time a request
completes. At that point, an aio_getevents() will return the completed result
to a struct io_event. I made a quick test program to verify the patch, and it
runs fine here:
http://www.xmailserver.org/eventfd-aio-test.c
The test program uses poll(2), but it'd, of course, work with select and epoll
too.
This can allow to schedule both block I/O and other poll-able devices
requests, and wait for results using select/poll/epoll. In a typical
scenario, an application would submit KAIO request using aio_submit(), and
will also use epoll_ctl() on the whole other class of devices (that with the
addition of signals, timers and user events, now it's pretty much complete),
and then would:
epoll_wait(...);
for_each_event {
if (curr_event_is_kaiofd) {
aio_getevents();
dispatch_aio_events();
} else {
dispatch_epoll_event();
}
}
Signed-off-by: Davide Libenzi <davidel@xmailserver.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This patch wires the eventfd system call to the x86 architectures.
Signed-off-by: Davide Libenzi <davidel@xmailserver.org>
Cc: Michael Kerrisk <mtk-manpages@gmx.net>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This is a very simple and light file descriptor, that can be used as event
wait/dispatch by userspace (both wait and dispatch) and by the kernel
(dispatch only). It can be used instead of pipe(2) in all cases where those
would simply be used to signal events. Their kernel overhead is much lower
than pipes, and they do not consume two fds. When used in the kernel, it can
offer an fd-bridge to enable, for example, functionalities like KAIO or
syslets/threadlets to signal to an fd the completion of certain operations.
But more in general, an eventfd can be used by the kernel to signal readiness,
in a POSIX poll/select way, of interfaces that would otherwise be incompatible
with it. The API is:
int eventfd(unsigned int count);
The eventfd API accepts an initial "count" parameter, and returns an eventfd
fd. It supports poll(2) (POLLIN, POLLOUT, POLLERR), read(2) and write(2).
The POLLIN flag is raised when the internal counter is greater than zero.
The POLLOUT flag is raised when at least a value of "1" can be written to the
internal counter.
The POLLERR flag is raised when an overflow in the counter value is detected.
The write(2) operation can never overflow the counter, since it blocks (unless
O_NONBLOCK is set, in which case -EAGAIN is returned).
But the eventfd_signal() function can do it, since it's supposed to not sleep
during its operation.
The read(2) function reads the __u64 counter value, and reset the internal
value to zero. If the value read is equal to (__u64) -1, an overflow happened
on the internal counter (due to 2^64 eventfd_signal() posts that has never
been retired - unlickely, but possible).
The write(2) call writes an __u64 count value, and adds it to the current
counter. The eventfd fd supports O_NONBLOCK also.
On the kernel side, we have:
struct file *eventfd_fget(int fd);
int eventfd_signal(struct file *file, unsigned int n);
The eventfd_fget() should be called to get a struct file* from an eventfd fd
(this is an fget() + check of f_op being an eventfd fops pointer).
The kernel can then call eventfd_signal() every time it wants to post an event
to userspace. The eventfd_signal() function can be called from any context.
An eventfd() simple test and bench is available here:
http://www.xmailserver.org/eventfd-bench.c
This is the eventfd-based version of pipetest-4 (pipe(2) based):
http://www.xmailserver.org/pipetest-4.c
Not that performance matters much in the eventfd case, but eventfd-bench
shows almost as double as performance than pipetest-4.
[akpm@linux-foundation.org: fix i386 build]
[akpm@linux-foundation.org: add sys_eventfd to sys_ni.c]
Signed-off-by: Davide Libenzi <davidel@xmailserver.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Dale Farnsworth