The documentation being added contains overall description of the LED Flash Class and the related sysfs attributes. There are also chapters devoted specifically to the Flash Manager feature. 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-flash.txt | 54 +++++++++++++++++++++++++++++++ 1 file changed, 54 insertions(+) create mode 100644 Documentation/leds/leds-class-flash.txt diff --git a/Documentation/leds/leds-class-flash.txt b/Documentation/leds/leds-class-flash.txt new file mode 100644 index 0000000..8a9c17e --- /dev/null +++ b/Documentation/leds/leds-class-flash.txt @@ -0,0 +1,54 @@ + +Flash LED handling under Linux +============================== + +Some LED devices support two modes - torch and flash. In order to enable +support for flash LEDs CONFIG_LEDS_CLASS_FLASH symbol must be defined +in the kernel config. A flash LED driver must register in the LED subsystem +with led_classdev_flash_register to gain flash capabilities. + +Following sysfs attributes are exposed for controlling flash led devices: + + - flash_brightness - flash LED brightness in microamperes (RW) + - max_flash_brightness - maximum available flash LED brightness (RO) + - indicator_brightness - privacy LED brightness in microamperes (RW) + - max_indicator_brightness - maximum privacy LED brightness in + microamperes (RO) + - flash_timeout - flash strobe duration in microseconds (RW) + - max_flash_timeout - maximum available flash strobe duration (RO) + - flash_strobe - flash strobe state (RW) + - external_strobe - some devices expose dedicated hardware pins for + triggering a flash LED - this attribute allows to + set this mode (RW) + - flash_fault - bitmask of flash faults that may have occurred, + 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 + +A LED subsystem driver can be controlled also from the level of VideoForLinux2 +subsystem. In order to enable this CONFIG_V4L2_FLASH_LED_CLASS symbol has to +be defined in the kernel config. The driver must call v4l2_flash_init function +to get registered in the V4L2 subsystem. On remove v4l2_flash_release function +has to be called (see <media/v4l2-flash.h>). + +After proper initialization V4L2 Flash sub-device is created. The 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. -- 1.7.9.5 -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
