Signed-off-by: Jacek Anaszewski <j.anaszewski@xxxxxxxxxxx> Acked-by: Kyungmin Park <kyungmin.park@xxxxxxxxxxx> Cc: Bryan Wu <cooloney@xxxxxxxxx> Cc: Richard Purdie <rpurdie@xxxxxxxxx> --- Documentation/leds/leds-class.txt | 52 +++++++++++++++++++++++++++++++++++++ 1 file changed, 52 insertions(+) diff --git a/Documentation/leds/leds-class.txt b/Documentation/leds/leds-class.txt index 62261c0..ea50d27 100644 --- a/Documentation/leds/leds-class.txt +++ b/Documentation/leds/leds-class.txt @@ -8,6 +8,58 @@ LED is defined in max_brightness file. The brightness file will set the brightne 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. +Some LED devices support two modes - torch and flash. In order to enable +support for flash LEDs the CONFIG_LEDS_CLASS_FLASH symbol must be defined +in the kernel config. A flash LED driver must initialize the "flash" field +of the led_classdev structure (see <linux/leds_flash.h>) to enable flash +related features of the LED subsystem for the driver. + +There are seven sysfs attributes dedicated specifically to the flash LED devices: + + - flash_brightness - flash LED brightness in milliampers (RW) + - max_flash_brightness - maximum available flash LED brightness (RO) + - flash_timeout - flash strobe duration in milliseconds (RW) + - max_flash_timeout - maximum available flash strobe duration (RO) + - flash_strobe - flash strobe state (RW) + - flash_fault - bitmask of flash faults that may have occured, possible + flags are: + * 0x01 - flash controller voltage to the flash LED has exceeded + the limit specific to the flash controller + * 0x02 - the flash strobe was still on when the timeout set by + the user has expired; not all flash controllers may set + this in all such conditions + * 0x04 - the flash controller has overheated + * 0x08 - the short circuit protection of the flash controller + has been triggered + * 0x10 - current in the LED power supply has exceeded the limit + specific to the flash controller + * 0x40 - flash controller voltage to the flash LED has been below + the minimum limit specific to the flash + * 0x80 - the input voltage of the flash controller is below + the limit under which strobing the flash at full current + will not be possible. The condition persists until this + flag is no longer set + * 0x100 - the temperature of the LED has exceeded its allowed + upper limit + - hw_triggered - some devices expose dedicated hardware pins for + triggering a flash LED - the attribute allows to set + this mode (RW) + +The LED subsystem driver can be controlled also from the level of +the VideoForLinux2 subsystem. In order to enable this the CONFIG_V4L2_FLASH +symbol has to be defined in the kernel config. The driver must +initialize v4l2_flash_ctrl_config structure and pass it to the v4l2_flash_init +function. On remove v4l2_flash_release has to be called (see <media/v4l2-flash.h>). +After proper initialization V4L2 Flash sub-device is created. The sub-device +must be registered by a V4L2 video device to become available for the user +space. This is accomplished with use of asynchronous sub-device registration +mechanism (see <media/v4l2-async.h>). +A V4l2 Flash sub-device exposes a number of V4L2 controls. +When the V4L2_CID_FLASH_LED_MODE control is set to V4L2_FLASH_LED_MODE_TORCH +or V4L2_FLASH_LED_MODE_FLASH the LED subsystem sysfs interface becomes +unavailable. The interface can be unlocked by setting the mode back +to V4L2_FLASH_LED_MODE_NONE. + 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 complex. A simple trigger isn't configurable and is designed to slot into -- 1.7.9.5 -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
