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led: document sysfs interface

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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>
This commit is contained in:
Corentin Chary 2009-08-28 12:56:45 +00:00 committed by Len Brown
parent 243ca3e401
commit 5f634c6527
2 changed files with 33 additions and 4 deletions
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28
Documentation/ABI/testing/sysfs-class-led Normal file
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What: /sys/class/leds/<led>/brightness
Date: March 2006
KernelVersion: 2.6.17
Contact: Richard Purdie <rpurdie@rpsys.net>
Description:
Set the brightness of the LED. Most LEDs don't
have hardware brightness support so will just be turned on for
non-zero brightness settings. The value is between 0 and
/sys/class/leds/<led>/max_brightness.
What: /sys/class/leds/<led>/max_brightness
Date: March 2006
KernelVersion: 2.6.17
Contact: Richard Purdie <rpurdie@rpsys.net>
Description:
Maximum brightness level for this led, default is 255 (LED_FULL).
What: /sys/class/leds/<led>/trigger
Date: March 2006
KernelVersion: 2.6.17
Contact: Richard Purdie <rpurdie@rpsys.net>
Description:
Set the trigger for this LED. A trigger is a kernel based source
of led events.
You can change triggers in a similar manner to the way an IO
scheduler is chosen. Trigger specific parameters can appear in
/sys/class/leds/<led> once a given trigger is selected.

9
Documentation/leds-class.txt
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@ -1,3 +1,4 @@
LED handling under Linux
========================
@ -5,10 +6,10 @@ If you're reading this and thinking about keyboard leds, these are
handled by the input subsystem and the led class is *not* needed.
In its simplest form, the LED class just allows control of LEDs from
userspace. LEDs appear in /sys/class/leds/. The brightness file will
set the brightness of the LED (taking a value 0-255). Most LEDs don't
have hardware brightness support so will just be turned on for non-zero
brightness settings.
userspace. LEDs appear in /sys/class/leds/. The maximum brightness of the
LED is defined in max_brightness file. The brightness file will set the brightness
of the LED (taking a value 0-max_brightness). Most LEDs don't have hardware
brightness support so will just be turned on for non-zero brightness settings.
The class also introduces the optional concept of an LED trigger. A trigger
is a kernel based source of led events. Triggers can either be simple or