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>
sysfs-class-led fails to mention some important details. Also fix led
vs LED and english.
Signed-off-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Jacek Anaszewski <j.anaszewski@samsung.com>
Documentation of sysfs interface should be in ABI in the first place.
This moves relevant part of documentation and mentions where to look for
it.
Fix trivial typos whilst we are at it.
Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Signed-off-by: Jacek Anaszewski <j.anaszewski@samsung.com>
Extend the LED backlight tirgger driver with an option that allows for
inverting the trigger output polarity.
With the invertion option provided, I (ab)use the backlight trigger for
driving a LED that indicates LCD display blank condtition on my Amstrad
Delta videophone. Since the machine has no dedicated power LED, it was
not possible to distinguish if the display was blanked, or the machine was
turned off, without touching it.
The invert sysfs control is patterned after a similiar function of the GPIO
trigger driver.
[akpm@linux-foundation.org: make output match input, tighten input checking]
[akpm@linux-foundation.org: make output match input, tighten input checking]
Signed-off-by: Janusz Krzysztofik <jkrzyszt@tis.icnet.pl>
Cc: Paul Mundt <lethal@linux-sh.org>
Acked-by: Richard Purdie <richard.purdie@linuxfoundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Also fix Documentation/led-class.txt, the acceptable
range of values for brightness is 0-max_brightness, not 0-255.
Cc: Richard Purdie <rpurdie@rpsys.net>
Signed-off-by: Corentin Chary <corentincj@iksaif.net>
Signed-off-by: Len Brown <len.brown@intel.com>
Hans de Goede