Documentation: leds: Add description of LED Flash class extension

The documentation being added contains overall description of the
LED Flash Class and the related sysfs attributes.

Signed-off-by: Jacek Anaszewski <j.anaszewski@samsung.com>
Acked-by: Kyungmin Park <kyungmin.park@samsung.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
Signed-off-by: Bryan Wu <cooloney@gmail.com>
This commit is contained in:
Jacek Anaszewski 2015-03-04 08:14:24 -08:00 committed by Bryan Wu
parent 9c4a8e138c
commit f6ad395bad

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Flash LED handling under Linux
==============================
Some LED devices provide two modes - torch and flash. In the LED subsystem
those modes are supported by LED class (see Documentation/leds/leds-class.txt)
and LED Flash class respectively. The torch mode related features are enabled
by default and the flash ones only if a driver declares it by setting
LED_DEV_CAP_FLASH flag.
In order to enable the support for flash LEDs CONFIG_LEDS_CLASS_FLASH symbol
must be defined in the kernel config. A LED Flash class driver must be
registered in the LED subsystem with led_classdev_flash_register function.
Following sysfs attributes are exposed for controlling flash LED devices:
(see Documentation/ABI/testing/sysfs-class-led-flash)
- flash_brightness
- max_flash_brightness
- flash_timeout
- max_flash_timeout
- flash_strobe
- flash_fault