Some LEDs may have their brightness level changed autonomously
(outside of kernel control) by hardware / firmware. This commit
adds support for an optional brightness_hw_changed attribute to
signal such changes to userspace (if a driver can detect them):
What: /sys/class/leds/<led>/brightness_hw_changed
Date: January 2017
KernelVersion: 4.11
Description:
Last hardware set brightness level for this LED. Some LEDs
may be changed autonomously by hardware/firmware. Only LEDs
where this happens and the driver can detect this, will
have this file.
This file supports poll() to detect when the hardware
changes the brightness.
Reading this file will return the last brightness level set
by the hardware, this may be different from the current
brightness.
Drivers which want to support this, simply add LED_BRIGHT_HW_CHANGED to
their flags field and call led_classdev_notify_brightness_hw_changed()
with the hardware set brightness when they detect a hardware / firmware
triggered brightness change.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Jacek Anaszewski <jacek.anaszewski@gmail.com>
Signed-off-by: Stephan Linz <linz@li-pro.net>
Cc: Joseph Jezak <josejx@gentoo.org>
Cc: Jörg Sommer <joerg@alea.gnuu.de>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Jacek Anaszewski <j.anaszewski@samsung.com>
Commit 76931edd54 ("leds: fix brightness changing when software blinking
is active") changed the semantics of led_set_brightness() which according
to the documentation should disable blinking upon any brightness setting.
Moreover it made it different for soft blink case, where it was possible
to change blink brightness, and for hardware blink case, where setting
any brightness greater than 0 was ignored.
While the change itself is against the documentation claims, it was driven
also by the fact that timer trigger remained active after turning blinking
off. Fixing that would have required major refactoring in the led-core,
led-class, and led-triggers because of cyclic dependencies.
Finally, it has been decided that allowing for brightness change during
blinking is beneficial as it can be accomplished without disturbing
blink rhythm.
The change in brightness setting semantics will not affect existing
LED class drivers that implement blink_set op thanks to the LED_BLINK_SW
flag introduced by this patch. The flag state will be from now on checked
in led_set_brightness() which will allow to distinguish between software
and hardware blink mode. In the latter case the control will be passed
directly to the drivers which apply their semantics on brightness set,
which is disable the blinking in case of most such drivers. New drivers
will apply new semantics and just change the brightness while hardware
blinking is on, if possible.
The issue was smuggled by subsequent LED core improvements, which modified
the code that originally introduced the problem.
Fixes: f1e80c0741 ("leds: core: Add two new LED_BLINK_ flags")
Signed-off-by: Tony Makkiel <tony.makkiel@daqri.com>
Signed-off-by: Jacek Anaszewski <j.anaszewski@samsung.com>
This patch adds description of the LED subsystem API for
setting an LED brightness.
Signed-off-by: Jacek Anaszewski <j.anaszewski@samsung.com>
Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>
This change creates a new input handler called "leds" that exports LEDs on input
devices as standard LED class devices in sysfs and allows controlling their
state via sysfs or via any of the standard LED triggers. This allows to
re-purpose and reassign LDEs on the keyboards to represent states other
than the standard keyboard states (CapsLock, NumLock, etc).
The old API of controlling input LEDs by writing into /dev/input/eventX
devices is still present and will take precedence over accessing via LEDs
subsystem (i.e. it may override state set by a trigger). If input device is
"grabbed" then requests coming through LED subsystem will be ignored.
Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Tested-by: Pavel Machek <pavel@ucw.cz>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
leds: move leds-class documentation under the leds/ subdir.
Add also a leds/00-INDEX file describing the files under leds/
Signed-off-by: Antonio Ospite <ospite@studenti.unina.it>
Acked-by: Richard Purdie <richard.purdie@linuxfoundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-04-04 17:51:47 -07:00
Renamed from Documentation/leds-class.txt (Browse further)
