percpu_rw_semaphore->writer_mutex was only added to simplify the initial
rewrite, the only thing it protects is clear_fast_ctr() which otherwise
could be called by multiple writers.  ->rw_sem is enough to serialize the
writers.

Kill this mutex and add "atomic_t write_ctr" instead.  The writers
increment/decrement this counter, the readers check it is zero instead of
mutex_is_locked().

Move atomic_add(clear_fast_ctr(), slow_read_ctr) under down_write() to
avoid the race with other writers.  This is a bit sub-optimal, only the
first writer needs this and we do not need to exclude the readers at this
stage.  But this is simple, we do not want another internal lock until we
add more features.

And this speeds up the write-contended case.  Before this patch the racing
writers sleep in synchronize_sched_expedited() sequentially, with this
patch multiple synchronize_sched_expedited's can "overlap" with each
other.  Note: we can do more optimizations, this is only the first step.
Signed-off-by: NOleg Nesterov <oleg@redhat.com>
Cc: Anton Arapov <anton@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michal Marek <mmarek@suse.cz>
Cc: Mikulas Patocka <mpatocka@redhat.com>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Currently the writer does msleep() plus synchronize_sched() 3 times to
acquire/release the semaphore, and during this time the readers are
blocked completely.  Even if the "write" section was not actually started
or if it was already finished.

With this patch down_write/up_write does synchronize_sched() twice and
down_read/up_read are still possible during this time, just they use the
slow path.

percpu_down_write() first forces the readers to use rw_semaphore and
increment the "slow" counter to take the lock for reading, then it
takes that rw_semaphore for writing and blocks the readers.

Also.  With this patch the code relies on the documented behaviour of
synchronize_sched(), it doesn't try to pair synchronize_sched() with
barrier.
Signed-off-by: NOleg Nesterov <oleg@redhat.com>
Reviewed-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mikulas Patocka <mpatocka@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Anton Arapov <anton@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This is another step towards better standard conformance.  Rather than
adding a local buffer to store the specified portion of the string (with
the need to enforce an arbitrary maximum supported width to limit the
buffer size), do a maximum width conversion and then drop as much of it as
is necessary to meet the caller's request.

Also fail on negative field widths.

Uses the deprecated simple_strto*() functions because kstrtoXX() fail on
non-zero terminated strings.
Signed-off-by: NJan Beulich <jbeulich@suse.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Signed-off-by: NAndy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: NGrant Likely <grant.likely@secretlab.ca>
Cc: Rob Herring <rob.herring@calxeda.com>
Cc: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Signed-off-by: NAndy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

[yongjun_wei@trendmicro.com.cn: remove duplicated include]
Signed-off-by: NAndy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: NWei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Signed-off-by: NAndy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Remove the custom implementation of the functionality similar to kbasename().
Signed-off-by: NAndy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Jason Baron <jbaron@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

There are several places in the kernel that use functionality like
basename(3) with the exception: in case of '/foo/bar/' we expect to get an
empty string.  Let's do it common helper for them.
Signed-off-by: NAndy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Jason Baron <jbaron@redhat.com>
Cc: YAMANE Toshiaki <yamanetoshi@gmail.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Signed-off-by: NMilo(Woogyom) Kim <milo.kim@ti.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Changing backlight intensity on an Akita (Sharp Zaurus C-1000) triggers
WARN_ON message:

  WARNING: at drivers/gpio/gpiolib.c:1672 __gpio_set_value+0x38/0xa4()
  Modules linked in:
  Backtrace:
    corgi_bl_set_intensity+0x0/0x74
    corgi_bl_update_status+0x0/0x64
    corgi_lcd_probe+0x0/0x258
    spi_drv_probe+0x0/0x24
    driver_probe_device+0x0/0x208
    __driver_attach+0x0/0x94
    bus_for_each_dev+0x0/0x90
    driver_attach+0x0/0x28
    bus_add_driver+0x0/0x22c
    driver_register+0x0/0x134
    spi_register_driver+0x0/0x60
    corgi_lcd_driver_init+0x0/0x1c
    do_one_initcall+0x0/0x174
    kernel_init+0x0/0x2a8

Akita machines have backlight controls hooked to a gpio expander chip,
max7310 using i2c transfers which can sleep.  In this case,
pca953x_gpio_set_value() can be called to control gpio, and
pca953x_setup_gpio() sets can_sleep flag.  Therefore,
gpio_set_value_cansleep() should be used in order to avoid WARN_ON on
akita machines.

Akita is the only exception in this case since other users of corgi_lcd
access backlight gpio controls through a different gpio expander which
does not set the can_sleep flag.
Signed-off-by: NMarko Katic <dromede@gmail.com>
Signed-off-by: NJingoo Han <jg1.han@samsung.com>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Grant Likely <grant.likely@secretlab.ca>
Cc: Florian Tobias Schandinat <FlorianSchandinat@gmx.de>
Cc: Richard Purdie <rpurdie@rpsys.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

GPIOF_DIR_OUT and GPIOF_DIR_IN are defined as below:

   GPIOF_DIR_OUT   (0 << 0)
   GPIOF_DIR_IN    (1 << 0)

So, when !pdata->reset_inverted is 1, the gpio pin can be set as
input, instead of output.

To prevent this problem, GPIOF_INIT flag should be used when using
devm_gpio_request_one().
Signed-off-by: NJingoo Han <jg1.han@samsung.com>
Cc: Marek Vasut <marex@denx.de>
Cc: Richard Purdie <rpurdie@rpsys.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Previously, when ops functions cannot be called, lcd_show_contrast() and
lcd_store_contrast() returned 0, instead of ENXIO.

Thus, in this case, a local variable 'rc' for return value should be
initialized as ENXIO, after kstrtoul() is called.
Signed-off-by: NJingoo Han <jg1.han@samsung.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Remove an unnecessary line continuation in pm860x_backlight_probe().
Also, a checkpatch warning is fixed as below:

  WARNING: Avoid unnecessary line continuations

[akpm@linux-foundation.org: remove newline]
Signed-off-by: NJingoo Han <jg1.han@samsung.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

TWL_MODULE_PWM is defined as:

  #define TWL_MODULE_PWM		TWL4030_MODULE_PWM0

Use the common module ID define here which will facilitate the upcoming
twl-core cleanup.
Signed-off-by: NPeter Ujfalusi <peter.ujfalusi@ti.com>
Acked-by: NJingoo Han <jg1.han@samsung.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
Cc: Florian Tobias Schandinat <FlorianSchandinat@gmx.de>
Cc: Grazvydas Ignotas <notasas@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This function finds the struct backlight_device for a given device tree
node.  A dummy function is provided so that it safely compiles out if OF
support is disabled.

[akpm@linux-foundation.org: Don't use IS_ENABLED(CONFIG_OF)]
Signed-off-by: NThierry Reding <thierry.reding@avionic-design.de>
Acked-by: NJingoo Han <jg1.han@samsung.com>
Reviewed-by: NGrant Likely <grant.likely@secretlab.ca>
Cc: Thierry Reding <thierry.reding@avionic-design.de>
Reviewed-by: NGrant Likely <grant.likely@secretlab.ca>
Acked-by: NJingoo Han <jg1.han@samsung.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

We don't need the sysfs file to be world writable or group writable.
This file is write-only, change it to S_IWUSR (0200).
Signed-off-by: NAxel Lin <axel.lin@ingics.com>
Acked-by: N"G.Shark Jeong" <gshark.jeong@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

devm_kfree() allocates memory that is released when a driver detaches.
Thus, there is no reason to explicitly call devm_kfree in probe or remove
functions.
Signed-off-by: NJingoo Han <jg1.han@samsung.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

devm_kfree() allocates memory that is released when a driver detaches.
Thus, there is no reason to explicitly call devm_kfree() in probe or remove
functions.
Signed-off-by: NJingoo Han <jg1.han@samsung.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Remove unnecessary cast of void pointer for platform data in probe
function.
Signed-off-by: NJingoo Han <jg1.han@samsung.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Add 'const' to static array that was missing it in its definition.  Also,
'const' is added to ili9320_write_regs(), because it is called by
vgg2432a4 driver.
Signed-off-by: NJingoo Han <jg1.han@samsung.com>
Cc: Ben Dooks <ben-linux@fluff.org>
Cc: Richard Purdie <rpurdie@rpsys.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Add 'const' to static array that was missing it in its definition.
Signed-off-by: NJingoo Han <jg1.han@samsung.com>
Cc: Eric Miao <eric.y.miao@gmail.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Add 'const' to static array that was missing it in its definition.
Signed-off-by: NJingoo Han <jg1.han@samsung.com>
Acked-by: NMarek Vasut <marex@denx.de>
Cc: Richard Purdie <rpurdie@rpsys.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Add 'const' to static array that was missing it in its definition.
Signed-off-by: NJingoo Han <jg1.han@samsung.com>
Cc: Ashish Jangam <ashish.jangam@kpitcummins.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The mutex for accessing lp855x registers is used in case of the user-space
interaction.  When the brightness is changed via sysfs, the mutex is
required.  But the backlight class device already provides it.  Thus, the
lp855x mutex is unnecessary.
Signed-off-by: NMilo(Woogyom) Kim <milo.kim@ti.com>
Cc: Thierry Reding <thierry.reding@avionic-design.de>
Cc: Richard Purdie <rpurdie@rpsys.net>
Cc: Bryan Wu <bryan.wu@canonical.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The LP855x family devices support the PWM input for the backlight control.
 Period of the PWM is configurable in the platform side.  Platform
specific functions are unnecessary anymore because generic PWM functions
are used inside the driver.

(PWM input mode)
To set the brightness, new lp855x_pwm_ctrl() is used.
If a PWM device is not allocated, devm_pwm_get() is called.
The PWM consumer name is from the chip name such as 'lp8550' and 'lp8556'.
To get the brightness value, no additional handling is required.
Just the value of 'props.brightness' is returned.

If the PWM driver is not ready while initializing the LP855x driver, it's
OK.  The PWM device can be retrieved later, when the brightness value is
changed.

Documentation is updated with an example.

[akpm@linux-foundation.org: coding-style simplification, per Thierry]
Signed-off-by: NMilo(Woogyom) Kim <milo.kim@ti.com>
Cc: Thierry Reding <thierry.reding@avionic-design.de>
Cc: Richard Purdie <rpurdie@rpsys.net>
Cc: Bryan Wu <bryan.wu@canonical.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

By using devm_gpio_request_one it is possible to set the direction and
initial value in one shot.  Thus, using devm_gpio_request_one can make the
code simpler.
Signed-off-by: NJingoo Han <jg1.han@samsung.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
Cc: Dmitry Baryshkov <dbaryshkov@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

By using devm_gpio_request_one it is possible to set the direction
and initial value in one shot. Thus, using devm_gpio_request_one
can make the code simpler.
Signed-off-by: NJingoo Han <jg1.han@samsung.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
Acked-by: NMarek Vasut <marex@denx.de>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This patch fixes the checkpatch warning as below:

  WARNING: please, no space before tabs
Signed-off-by: NJingoo Han <jg1.han@samsung.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This patch fixes the checkpatch error and warning as below:

  ERROR: spaces required around that '?' (ctx:VxW)
  ERROR: space required after that ',' (ctx:VxV)

Also, unnecessary lines are removed.
Signed-off-by: NJingoo Han <jg1.han@samsung.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This patch fixes the checkpatch warning as below:

  WARNING: please, no space before tabs
Signed-off-by: NJingoo Han <jg1.han@samsung.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This patch fixes the checkpatch error as below:

  ERROR: spaces prohibited around that ':' (ctx:WxW)
Signed-off-by: NJingoo Han <jg1.han@samsung.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This patch fixes the checkpatch warning as below:

  WARNING: please, no spaces at the start of a line

Also, long comments are fixed for the preferred style.
Signed-off-by: NJingoo Han <jg1.han@samsung.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This patch fixes the checkpatch warning as below:

  ERROR: inline keyword should sit between storage class and type
Signed-off-by: NJingoo Han <jg1.han@samsung.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This patch fixes the checkpatch warning as below:

  WARNING: static const char * array should probably be static const char * const
Signed-off-by: NJingoo Han <jg1.han@samsung.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This patch fixes the checkpatch warning as below:

  WARNING: please, no space before tabs

Also, unnecessary line is removed.
Signed-off-by: NJingoo Han <jg1.han@samsung.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This patch fixes the checkpatch error and warning as below:

  ERROR: return is not a function, parentheses are not required

Also, long comments are fixed for the preferred style.
Signed-off-by: NJingoo Han <jg1.han@samsung.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This patch fixes the checkpatch error and warning as below:

  WARNING: please, no space before tabs
  WARNING: please, no spaces at the start of a line
  WARNING: EXPORT_SYMBOL(foo); should immediately follow its function/variable
  WARNING: braces {} are not necessary for single statement blocks
  ERROR: code indent should use tabs where possible
Signed-off-by: NJingoo Han <jg1.han@samsung.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This patch fixes the checkpatch error and warning as below:

  WARNING: please, no space before tabs
  WARNING: please, no spaces at the start of a line
  ERROR: do not initialise statics to 0 or NULL
  ERROR: code indent should use tabs where possible
Signed-off-by: NJingoo Han <jg1.han@samsung.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This patch fixes the checkpatch warning as below:

  WARNING: space prohibited between function name and open parenthesis '('
Signed-off-by: NJingoo Han <jg1.han@samsung.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>