Documentation: leds: Add description of LED Flash class extension

[mirror_ubuntu-bionic-kernel.git] / Documentation / leds / leds-class-flash.txt

Flash LED handling under Linux
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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