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[ Upstream commitcec2b18832] gpiod_get_value() gives out a warning if access to the underlying gpiochip requires sleeping, which is common for I2C based chips: WARNING: CPU: 0 PID: 77 at drivers/gpio/gpiolib.c:2500 gpiod_get_value+0xd0/0x100 Modules linked in: CPU: 0 PID: 77 Comm: kworker/0:2 Not tainted 4.14.0-rc3-00589-gf32897915d48-dirty #90 Hardware name: Allwinner sun4i/sun5i Families Workqueue: events deferred_probe_work_func [<c010ec50>] (unwind_backtrace) from [<c010b784>] (show_stack+0x10/0x14) [<c010b784>] (show_stack) from [<c0797224>] (dump_stack+0x88/0x9c) [<c0797224>] (dump_stack) from [<c0125b08>] (__warn+0xe8/0x100) [<c0125b08>] (__warn) from [<c0125bd0>] (warn_slowpath_null+0x20/0x28) [<c0125bd0>] (warn_slowpath_null) from [<c037069c>] (gpiod_get_value+0xd0/0x100) [<c037069c>] (gpiod_get_value) from [<c03778d0>] (pwm_backlight_probe+0x238/0x508) [<c03778d0>] (pwm_backlight_probe) from [<c0411a2c>] (platform_drv_probe+0x50/0xac) [<c0411a2c>] (platform_drv_probe) from [<c0410224>] (driver_probe_device+0x238/0x2e8) [<c0410224>] (driver_probe_device) from [<c040e820>] (bus_for_each_drv+0x44/0x94) [<c040e820>] (bus_for_each_drv) from [<c040ff0c>] (__device_attach+0xb0/0x114) [<c040ff0c>] (__device_attach) from [<c040f4f8>] (bus_probe_device+0x84/0x8c) [<c040f4f8>] (bus_probe_device) from [<c040f944>] (deferred_probe_work_func+0x50/0x14c) [<c040f944>] (deferred_probe_work_func) from [<c013be84>] (process_one_work+0x1ec/0x414) [<c013be84>] (process_one_work) from [<c013ce5c>] (worker_thread+0x2b0/0x5a0) [<c013ce5c>] (worker_thread) from [<c0141908>] (kthread+0x14c/0x154) [<c0141908>] (kthread) from [<c0107ab0>] (ret_from_fork+0x14/0x24) This was missed in commit0c9501f823("backlight: pwm_bl: Handle gpio that can sleep"). The code was then moved to a separate function in commit7613c92231("backlight: pwm_bl: Move the checks for initial power state to a separate function"). The only usage of gpiod_get_value() is during the probe stage, which is safe to sleep in. Switch to gpiod_get_value_cansleep(). Fixes:0c9501f823("backlight: pwm_bl: Handle gpio that can sleep") Signed-off-by: Chen-Yu Tsai <wens@csie.org> Acked-by: Maxime Ripard <maxime.ripard@bootlin.com> Acked-by: Daniel Thompson <daniel.thompson@linaro.org> Signed-off-by: Lee Jones <lee.jones@linaro.org> Signed-off-by: Sasha Levin <sashal@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.