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Commit 5f634c65 authored by Corentin Chary's avatar Corentin Chary Committed by Len Brown
Browse files

led: document sysfs interface 



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: default avatarCorentin Chary <corentincj@iksaif.net>
Signed-off-by: default avatarLen Brown <len.brown@intel.com>
parent 243ca3e4

Documentation/ABI/testing/sysfs-class-led

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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.

Documentation/leds-class.txt

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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