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Yoshihiro YUNOMAE aef9a7bd9b serial/uart/8250: Add tunable RX interrupt trigger I/F of FIFO buffers 
Add tunable RX interrupt trigger I/F of FIFO buffers.

Serial devices are used as not only message communication devices but control
or sending communication devices. For the latter uses, normally small data
will be exchanged, so user applications want to receive data unit as soon as
possible for real-time tendency. If we have a sensor which sends a 1 byte data
each time and must control a device based on the sensor feedback, the RX
interrupt should be triggered for each data.

According to HW specification of serial UART devices, RX interrupt trigger
can be changed, but the trigger is hard-coded. For example, RX interrupt trigger
in 16550A can be set to 1, 4, 8, or 14 bytes for HW, but current driver sets
the trigger to only 8bytes.

This patch makes some devices change RX interrupt trigger from userland.

<How to use>
- Read current setting
 # cat /sys/class/tty/ttyS0/rx_trig_bytes
 8

- Write user setting
 # echo 1 > /sys/class/tty/ttyS0/rx_trig_bytes
 # cat /sys/class/tty/ttyS0/rx_trig_bytes
 1

<Support uart devices>
- 16550A and Tegra (1, 4, 8, or 14 bytes)
- 16650V2 (8, 16, 24, or 28 bytes)
- 16654 (8, 16, 56, or 60 bytes)
- 16750 (1, 16, 32, or 56 bytes)

<Change log>
Changes in V9:
 - Use attr_group instead of dev_spec_attr_group of uart_port structure

Changes in V8:
 - Divide this patch from V7's patch based on Greg's comment

Changes in V7:
 - Add Documentation
 - Change I/F name from rx_int_trig to rx_trig_bytes because the name
   rx_int_trig is hard to understand how users specify the value

Changes in V6:
 - Move FCR_RX_TRIG_* definition in 8250.h to include/uapi/linux/serial_reg.h,
   rename those to UART_FCR_R_TRIG_*, and use UART_FCR_TRIGGER_MASK to
   UART_FCR_R_TRIG_BITS()
 - Change following function names:
    convert_fcr2val() => fcr_get_rxtrig_bytes()
    convert_val2rxtrig() => bytes_to_fcr_rxtrig()
 - Fix typo in serial8250_do_set_termios()
 - Delete the verbose error message pr_info() in bytes_to_fcr_rxtrig()
 - Rename *rx_int_trig/rx_trig* to *rxtrig* for several functions or variables
   (but UI remains rx_int_trig)
 - Change the meaningless variable name 'val' to 'bytes' following functions:
    fcr_get_rxtrig_bytes(), bytes_to_fcr_rxtrig(), do_set_rxtrig(),
    do_serial8250_set_rxtrig(), and serial8250_set_attr_rxtrig()
 - Use up->fcr in order to get rxtrig_bytes instead of rx_trig_raw in
   fcr_get_rxtrig_bytes()
 - Use conf_type->rxtrig_bytes[0] instead of switch statement for support check
   in register_dev_spec_attr_grp()
 - Delete the checking whether a user changed FCR or not when minimum buffer
   is needed in serial8250_do_set_termios()

Changes in V5.1:
 - Fix FCR_RX_TRIG_MAX_STATE definition

Changes in V5:
 - Support Tegra, 16650V2, 16654, and 16750
 - Store default FCR value to up->fcr when the port is first created
 - Add rx_trig_byte[] in uart_config[] for each device and use rx_trig_byte[]
   in convert_fcr2val() and convert_val2rxtrig()

Changes in V4:
 - Introduce fifo_bug flag in uart_8250_port structure
   This is enabled only when parity is enabled and UART_BUG_PARITY is enabled
   for up->bugs. If this flag is enabled, user cannot set RX trigger.
 - Return -EOPNOTSUPP when it does not support device at convert_fcr2val() and
   at convert_val2rxtrig()
 - Set the nearest lower RX trigger when users input a meaningless value at
   convert_val2rxtrig()
 - Check whether p->fcr is existing at serial8250_clear_and_reinit_fifos()
 - Set fcr = up->fcr in the begging of serial8250_do_set_termios()

Changes in V3:
 - Change I/F from ioctl(2) to sysfs(rx_int_trig)

Changed in V2:
 - Use _IOW for TIOCSFIFORTRIG definition
 - Pass the interrupt trigger value itself

Signed-off-by: Yoshihiro YUNOMAE <yoshihiro.yunomae.ez@hitachi.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
 		2014-07-17 18:23:35 -07:00
..
ABI serial/uart/8250: Add tunable RX interrupt trigger I/F of FIFO buffers 2014-07-17 18:23:35 -07:00
DocBook DocBook: fix various typos 2014-07-12 11:30:36 -07:00
EDID drm: Add 800x600 (SVGA) screen resolution to the built-in EDIDs 2014-05-26 12:53:40 +10:00
PCI Merge branch 'pci/dead-code' into next 2014-02-20 14:32:34 -07:00
RCU documentation: Update API documentation 2014-04-29 08:38:53 -07:00
accounting Documentation/accounting/getdelays.c: add missing null-terminate after strncpy call 2014-06-23 16:47:44 -07:00
acpi Documentation / ACPI: Fix location of GPIO documentation 2014-05-23 14:39:26 +02:00
aoe aoe: remove do-nothing NAME="%k" term from example udev rules 2013-09-11 15:59:28 -07:00
arm Merge branch 'for-linus' of git://ftp.arm.linux.org.uk/~rmk/linux-arm into next 2014-06-05 15:57:04 -07:00
arm64 doc: arm64: add description of EFI stub support 2014-04-30 19:57:05 +01:00
auxdisplay
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backlight backlight: lp855x_bl: support new LP8555 device 2013-11-13 12:09:14 +09:00
blackfin Documentation/: update 00-INDEX files 2014-02-10 16:01:40 -08:00
block Documentation/: update 00-INDEX files 2014-02-10 16:01:40 -08:00
blockdev zram: propagate error to user 2014-04-07 16:36:02 -07:00
bus-devices
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cdrom
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cgroups Merge branch 'for-3.16' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup 2014-06-09 15:03:33 -07:00
connector w1: optional bundling of netlink kernel replies 2014-05-27 13:56:21 -07:00
console
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cpu-freq intel_pstate: Update documentation of {max,min}_perf_pct sysfs files 2014-07-07 01:22:19 +02:00
cpuidle cpuidle: remove cpuidle_unregister_governor() 2013-10-30 01:21:24 +01:00
cris
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crypto drivers/dma: remove unused support for MEMSET operations 2013-07-03 16:07:42 -07:00
development-process Documentation: development-process: Update -mm and -next URLs 2013-07-25 12:37:24 +02:00
device-mapper dm thin: add 'no_space_timeout' dm-thin-pool module param 2014-05-20 14:30:36 -04:00
devicetree serial: samsung: get fifosize via device tree 2014-07-17 18:18:22 -07:00
driver-model Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2014-06-12 14:27:40 -07:00
dvb Linux 3.14-rc5 2014-03-11 06:55:49 -03:00
early-userspace Documentation: remove reference to 2.7 kernel in early-userspace 2013-08-20 12:47:28 +02:00
extcon extcon: fix switch class porting guide (Documentation) 2014-01-07 11:54:28 +09:00
fault-injection
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fb doc: spelling error changes 2014-05-05 15:32:05 +02:00
filesystems Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2014-06-12 10:30:18 -07:00
firmware_class
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fmc FMC: make eeprom attribute writable 2014-02-28 15:12:08 -08:00
frv
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gpio Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial into next 2014-06-04 08:50:34 -07:00
hid Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial into next 2014-06-04 08:50:34 -07:00
hwmon hwmon: (ntc_thermistor) Use the manufacturer name properly 2014-06-25 07:09:13 -07:00
i2c Documentation: i2c: improve section about flags mangling the protocol 2014-04-06 13:53:48 +02:00
i2o
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ia64
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ide Documentation/: update 00-INDEX files 2014-02-10 16:01:40 -08:00
infiniband
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input Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial into next 2014-06-04 08:50:34 -07:00
ioctl s390/hypfs: add interface for diagnose 0x304 2014-01-24 09:40:59 +01:00
isdn
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ja_JP Documentation: Update stable address in Chinese and Japanese translations 2014-04-16 14:13:27 -07:00
kbuild kbuild: fix a typo in a kbuild document 2014-06-18 21:38:18 +02:00
kdump Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2013-07-04 11:40:58 -07:00
ko_KR Documentation: HOWTO: Updates on subsystem trees, patchwork, -next (vs. -mm) in ko_KR 2014-01-08 15:32:51 -08:00
laptops Documenation/laptops: rename and update hpfall.c 2014-07-12 11:30:37 -07:00
leds Documentation/: update 00-INDEX files 2014-02-10 16:01:40 -08:00
m68k Documentation/: update 00-INDEX files 2014-02-10 16:01:40 -08:00
make
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memory-devices
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metag
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mic misc: mic: Fix endianness issues. 2013-11-27 11:03:38 -08:00
mips
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misc-devices Merge branch 'hwmon-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jdelvare/staging 2014-01-29 18:56:27 -08:00
mmc
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mn10300
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mtd MTD updates for 3.16: 2014-06-11 08:35:34 -07:00
namespaces
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netlabel
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networking Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2014-06-12 14:27:40 -07:00
nfc
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parisc parisc: document the shadow registers 2013-07-09 22:09:19 +02:00
pcmcia
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phy phy: Add new Exynos USB 2.0 PHY driver 2014-03-08 12:39:44 +05:30
platform Documentation: Add list of laptop models supported by the Compal driver 2014-06-10 19:11:06 -04:00
power PM / Documentation: Update copyright in suspend-and-cpuhotplug.txt 2014-06-09 22:54:15 +02:00
powerpc Merge branch 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/benh/powerpc 2014-06-10 18:54:22 -07:00
pps USB: serial: invoke dcd_change ldisc's handler. 2013-09-26 09:45:40 -07:00
prctl
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pti
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ptp ptp: In the testptp utility, use clock_adjtime from glibc when available 2014-06-16 21:32:31 -07:00
rapidio rapidio: rework device hierarchy and introduce mport class of devices 2014-04-07 16:36:07 -07:00
s390 Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial into next 2014-06-04 08:50:34 -07:00
scheduler asm/system.h: clean asm/system.h from docs 2014-04-07 16:36:11 -07:00
scsi qla2xxx: Change copyright year to 2014 in all the source files. 2014-05-19 13:31:02 +02:00
security Merge branch 'serge-next-1' of git://git.kernel.org/pub/scm/linux/kernel/git/sergeh/linux-security 2014-06-10 10:05:36 -07:00
serial tty/serial: Add GPIOLIB helpers for controlling modem lines 2014-05-28 12:49:14 -07:00
sh
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sound ALSA: hda - Adjust speaker HPF and add LED support for HP Spectre 13 2014-06-25 17:50:24 +02:00
spi Merge remote-tracking branches 'spi/topic/s3c64xx', 'spi/topic/sc18is602', 'spi/topic/sh-hspi', 'spi/topic/sh-msiof', 'spi/topic/sh-sci', 'spi/topic/sirf' and 'spi/topic/spidev' into spi-next 2014-03-30 00:51:34 +00:00
sysctl kernel/watchdog.c: print traces for all cpus on lockup detection 2014-06-23 16:47:44 -07:00
target target: Remove TF_CIT_TMPL macro 2013-10-16 13:35:02 -07:00
thermal drm/nouveau/doc: update the thermal documentation 2014-06-17 14:50:17 +10:00
timers timer_stats/doc: Fix /proc/timer_stats documentation 2014-05-04 20:46:32 +02:00
tpm drivers/tpm: add xen tpmfront interface 2013-08-09 10:57:06 -04:00
trace mm:vmscan: update the trace-vmscan-postprocess.pl for event vmscan/mm_vmscan_lru_isolate 2014-07-03 09:21:54 -07:00
usb Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial into next 2014-06-04 08:50:34 -07:00
vDSO x86/vdso/doc: Make vDSO examples more portable 2014-06-12 19:01:24 -07:00
video4linux [media] exynos4-is: Remove support for non-dt platforms 2014-05-23 18:52:54 -03:00
virtual Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial into next 2014-06-04 08:50:34 -07:00
vm mm: mark remap_file_pages() syscall as deprecated 2014-06-06 16:08:17 -07:00
w1 w1: optional bundling of netlink kernel replies 2014-05-27 13:56:21 -07:00
watchdog watchdog: it87_wdt: Work around non-working CIR interrupts 2014-03-31 13:33:55 +02:00
wimax
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x86 Merge branch 'x86/espfix' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip into next 2014-06-05 07:46:15 -07:00
xtensa xtensa: remap io area defined in device tree 2014-01-15 00:25:14 +04:00
zh_CN driver core fixes for 3.15-rc2 2014-04-18 16:59:52 -07:00
.gitignore
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00-INDEX Merge branch 'x86-nuke-platforms-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2014-04-02 13:15:58 -07:00
BUG-HUNTING
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Changes Documentation/Changes: clean up mcelog paragraph 2014-07-12 11:30:36 -07:00
CodingStyle Documentation: expand/clarify debug documentation 2014-06-04 16:54:17 -07:00
DMA-API-HOWTO.txt DMA-API: Update dma_pool_create ()and dma_pool_alloc() descriptions 2014-05-26 17:28:28 -06:00
DMA-API.txt DMA-API: Capitalize "CPU" consistently 2014-05-26 17:28:27 -06:00
DMA-ISA-LPC.txt DMA-API: Clarify physical/bus address distinction 2014-05-20 16:54:21 -06:00
DMA-attributes.txt doc: spelling error changes 2014-05-05 15:32:05 +02:00
HOWTO Documentation: HOWTO: Update broken links to tpp 2013-12-10 23:09:08 -08:00
IPMI.txt
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IRQ-affinity.txt doc: fix a typo about irq affinity 2013-08-20 12:59:18 +02:00
IRQ-domain.txt genirq: Improve documentation to match current implementation 2014-05-27 10:16:44 +02:00
IRQ.txt
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Intel-IOMMU.txt
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Makefile
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ManagementStyle
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SAK.txt
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SM501.txt
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SecurityBugs
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SubmitChecklist
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SubmittingDrivers
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SubmittingPatches Documentation/SubmittingPatches: describe the Fixes: tag 2014-06-06 16:08:11 -07:00
VGA-softcursor.txt
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applying-patches.txt
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assoc_array.txt KEYS: Fix multiple key add into associative array 2013-12-02 11:24:18 +00:00
atomic_ops.txt arch,doc: Convert smp_mb__*() 2014-04-18 14:20:48 +02:00
bad_memory.txt
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basic_profiling.txt
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bcache.txt Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2013-07-04 11:40:58 -07:00
binfmt_misc.txt
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braille-console.txt
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bt8xxgpio.txt
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btmrvl.txt
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bus-virt-phys-mapping.txt
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cachetlb.txt Documentation: fix typo and update version in cachetlb.txt 2013-08-20 12:46:52 +02:00
circular-buffers.txt documentation: Update circular buffer for load-acquire/store-release 2013-12-03 10:08:57 -08:00
clk.txt clk: Improve clk_ops documentation 2014-05-12 17:08:33 -07:00
coccinelle.txt Coccinelle: Update information about the minimal version required 2013-07-03 22:58:20 +02:00
cpu-hotplug.txt Doc/cpu-hotplug: Specify race-free way to register CPU hotplug callbacks 2014-03-20 13:43:40 +01:00
cpu-load.txt
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cputopology.txt doc: Documentation/cputopology.txt fix typo 2013-09-04 12:59:47 +02:00
crc32.txt
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dcdbas.txt
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debugging-modules.txt
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debugging-via-ohci1394.txt firewire: revert to 4 GB RDMA, fix protocols using Memory Space 2014-05-29 15:50:30 +02:00
dell_rbu.txt
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devices.txt Merge branch 'v4l_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media 2014-04-04 09:50:07 -07:00
digsig.txt
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dma-buf-sharing.txt doc: spelling error changes 2014-05-05 15:32:05 +02:00
dmaengine.txt
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dmatest.txt dmatest: add a 'wait' parameter 2013-11-14 11:04:40 -08:00
dontdiff Documentation: LLVMLinux: Update Documentation/dontdiff 2014-04-09 13:44:34 -07:00
dynamic-debug-howto.txt doc: spelling error changes 2014-05-05 15:32:05 +02:00
edac.txt Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial into next 2014-06-04 08:50:34 -07:00
efi-stub.txt doc: arm64: add description of EFI stub support 2014-04-30 19:57:05 +01:00
eisa.txt
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email-clients.txt Documentation: add section about git to email-clients.txt 2014-06-29 13:38:33 -07:00
flexible-arrays.txt
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futex-requeue-pi.txt doc: fix double words 2014-03-21 13:16:58 +01:00
gcov.txt gcov: compile specific gcov implementation based on gcc version 2013-11-13 12:09:34 +09:00
highuid.txt
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hsi.txt Documentation: HSI: Add some general description for the HSI subsystem 2014-05-04 09:49:46 +02:00
hw_random.txt
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hwspinlock.txt doc: documentation/hwspinlock.txt fix typo 2013-08-27 10:46:02 +02:00
init.txt
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initrd.txt
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intel_txt.txt
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io-mapping.txt doc: fix some typos 2013-12-02 14:48:28 +01:00
io_ordering.txt
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iostats.txt
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irqflags-tracing.txt asm/system.h: clean asm/system.h from docs 2014-04-07 16:36:11 -07:00
isapnp.txt
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java.txt Documentation: update java sample wrapper for java 7 2014-05-25 12:39:00 -07:00
kernel-doc-nano-HOWTO.txt
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kernel-docs.txt
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kernel-parameters.txt kernel/watchdog.c: print traces for all cpus on lockup detection 2014-06-23 16:47:44 -07:00
kernel-per-CPU-kthreads.txt Documentation/kernel-per-CPU-kthreads.txt: Workqueue affinity 2014-02-17 14:56:08 -08:00
kmemcheck.txt doc: fix double words 2014-03-21 13:16:58 +01:00
kmemleak.txt mm: introduce kmemleak_update_trace() 2014-06-06 16:08:17 -07:00
kobject.txt kobject: remove kset from sysfs immediately in kset_unregister() 2013-12-07 21:20:11 -08:00
kprobes.txt kprobes: Introduce NOKPROBE_SYMBOL() macro to maintain kprobes blacklist 2014-04-24 10:02:56 +02:00
kref.txt
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ldm.txt
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local_ops.txt
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lockdep-design.txt
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lockstat.txt lockstat: Report avg wait and hold times 2013-10-09 08:19:08 +02:00
lockup-watchdogs.txt
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logo.gif
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logo.txt
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magic-number.txt Documentation/serial: Delete obsolete driver documentation 2014-04-16 14:20:34 -07:00
md.txt doc: fix some typos in documentations 2013-12-02 14:45:19 +01:00
media-framework.txt Merge branch 'v4l_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media 2013-07-13 12:09:57 -07:00
memory-barriers.txt Documentation/memory-barriers.txt: fix important typo re memory barriers 2014-06-06 16:08:11 -07:00
memory-hotplug.txt mm, hotplug: probe interface is available on several platforms 2014-06-23 16:47:43 -07:00
module-signing.txt Nothing major: the stricter permissions checking for sysfs broke 2014-04-06 09:38:07 -07:00
mono.txt
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mutex-design.txt locking/mutexes: Documentation update/rewrite 2014-06-05 13:29:37 +02:00
nommu-mmap.txt
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numastat.txt
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oops-tracing.txt Use 'E' instead of 'X' for unsigned module taint flag. 2014-03-31 14:52:43 +10:30
padata.txt
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parport-lowlevel.txt
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parport.txt
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percpu-rw-semaphore.txt
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phy.txt drivers: phy: Add support for optional phys 2014-02-05 05:48:43 +00:00
pi-futex.txt
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pinctrl.txt pinctrl: Fix some typos and grammar issues in the documentation 2014-01-15 13:59:50 +01:00
pnp.txt
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preempt-locking.txt
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printk-formats.txt doc: printk-formats: do not mention casts for u64/s64 2014-05-05 15:32:42 +02:00
pwm.txt pwm: modify PWM_LOOKUP to initialize all struct pwm_lookup members 2014-05-21 11:19:36 +02:00
ramoops.txt
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rbtree.txt doc: spelling error changes 2014-05-05 15:32:05 +02:00
remoteproc.txt
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rfkill.txt doc: spelling error changes 2014-05-05 15:32:05 +02:00
robust-futex-ABI.txt Documentation/robust-futex-API: Count properly to 4 2013-11-30 14:08:28 +01:00
robust-futexes.txt doc: spelling error changes 2014-05-05 15:32:05 +02:00
rpmsg.txt
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rt-mutex-design.txt doc: fix some typos in documentations 2013-12-02 14:45:19 +01:00
rt-mutex.txt
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rtc.txt rtc: add ability to push out an existing wakealarm using sysfs 2013-07-03 16:07:54 -07:00
serial-console.txt
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sgi-ioc4.txt
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smsc_ece1099.txt
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sparse.txt
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spinlocks.txt sched: Rename sched.c as sched/core.c in comments and Documentation 2013-06-19 12:58:42 +02:00
stable_api_nonsense.txt
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stable_kernel_rules.txt stable_kernel_rules: spelling/word usage 2014-04-16 14:13:26 -07:00
static-keys.txt doc: fix some typos in documentations 2013-12-02 14:45:19 +01:00
svga.txt
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sysfs-rules.txt doc: Fix typo in doucmentations 2013-07-25 12:34:15 +02:00
sysrq.txt sysrq: Allow magic SysRq key functions to be disabled through Kconfig 2013-10-16 13:01:44 -07:00
this_cpu_ops.txt
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unaligned-memory-access.txt ether_addr_equal: Optimize implementation, remove unused compare_ether_addr 2013-12-06 16:37:43 -05:00
unicode.txt
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unshare.txt
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vfio.txt vfio: fix documentation 2013-09-05 16:36:21 -06:00
vgaarbiter.txt
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video-output.txt
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vme_api.txt VME: Rename vme_slot_get to avoid confusion with reference counting 2013-12-03 11:15:58 -08:00
volatile-considered-harmful.txt
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workqueue.txt workqueue: Correct/Drop references to gcwq in Documentation 2013-08-21 10:32:09 -04:00
ww-mutex-design.txt mutex: Add support for wound/wait style locks 2013-06-26 12:10:56 +02:00
xz.txt
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zorro.txt zorro/UAPI: Disintegrate include/linux/zorro*.h 2013-11-26 11:09:08 +01:00