This patch extends LED Flash class documention by the description of interactions with v4l2-flash sub-device. 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 | 47 +++++++++++++++++++++++++++++++ 1 file changed, 47 insertions(+) diff --git a/Documentation/leds/leds-class-flash.txt b/Documentation/leds/leds-class-flash.txt index 19bb673..9d39133 100644 --- a/Documentation/leds/leds-class-flash.txt +++ b/Documentation/leds/leds-class-flash.txt @@ -20,3 +20,50 @@ Following sysfs attributes are exposed for controlling flash LED devices: - max_flash_timeout - flash_strobe - flash_fault + + +V4L2 flash wrapper for flash LEDs +================================= + +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 the v4l2_flash_init function to get registered in the +V4L2 subsystem. The function takes three arguments: +- fled_cdev : the LED Flash class device to wrap +- ops : V4L2 specific ops + * external_strobe_set - defines the source of the flash LED strobe - + V4L2_CID_FLASH_STROBE control or external source, typically + a sensor, which makes it possible to synchronise the flash + strobe start with exposure start, + * intensity_to_led_brightness and led_brightness_to_intensity - perform + enum led_brightness <-> V4L2 intensity conversion in a device + specific manner - they can be used for devices with non-linear + LED current scale. +- config : configuration for V4L2 Flash sub-device + * dev_name - the name of the media entity, unique in the system, + * flash_faults - bitmask of flash faults that the LED Flash class + device can report; corresponding LED_FAULT* bit definitions are + available in <linux/led-class-flash.h>, + * intensity - constraints for the LED in the TORCH or INDICATOR mode, + in microamperes, + * has_external_strobe - determines whether the flash strobe source + can be switched to external, + * indicator_led - signifies that a led is of indicator type, which + implies that it can have only two V4L2 controls: + V4L2_CID_FLASH_INDICATOR_INTENSITY and V4L2_CID_FLASH_FAULT. + +On remove the v4l2_flash_release function has to be called, which takes one +argument - struct v4l2_flash pointer returned previously by v4l2_flash_init. + +Please refer to drivers/leds/leds-max77693.c for an exemplary usage of the +v4l2 flash API. + +Once the V4L2 sub-device is registered by the driver which created the Media +controller device, the sub-device node acts just as a node of a native V4L2 +flash API device would. The calls are simply routed to the LED flash API. + +Opening the V4L2 flash sub-device makes the LED subsystem sysfs interface +unavailable. The interface is re-enabled after the V4L2 flash sub-device +is closed. -- 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
