Re: [PATCH v2 09/11] Documentation: leds: Add description of v4l2-flash sub-device

Sakari Ailus
2015-03-28T23:36:09Z

Hi Jacek,

On Fri, Mar 27, 2015 at 02:49:43PM +0100, Jacek Anaszewski wrote:
> This patch extends LED Flash class documention by
> the description of interactions with v4l2-flash sub-device.
>
> Signed-off-by: Jacek Anaszewski <j.anaszewski@samsung.com>
> Acked-by: Kyungmin Park <kyungmin.park@samsung.com>
> Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>
> Cc: Bryan Wu <cooloney@gmail.com>
> Cc: Richard Purdie <rpurdie@rpsys.net>
> ---
> Documentation/leds/leds-class-flash.txt | 13 +++++++++++++
> 1 file changed, 13 insertions(+)
>
> diff --git a/Documentation/leds/leds-class-flash.txt b/Documentation/leds/leds-class-flash.txt
> index 19bb673..8623413 100644
> --- a/Documentation/leds/leds-class-flash.txt
> +++ b/Documentation/leds/leds-class-flash.txt
> @@ -20,3 +20,16 @@ Following sysfs attributes are exposed for controlling flash LED devices:
> - max_flash_timeout
> - flash_strobe
> - flash_fault
> +
> +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. On remove the
> +v4l2_flash_release function has to be called (see <media/v4l2-flash.h>).

More information on using the interface functions would be nice, with a
pointer to a driver that uses the interface. The simpler, the better I
guess.

> +
> +After proper initialization a V4L2 Flash sub-device is created. The sub-device
> +exposes a number of V4L2 controls, which allow for controlling a LED Flash class
> +device with use of its internal kernel API.

How about this:

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.

--
Kind regards,

Sakari Ailus
e-mail: sakari.ailus@iki.fi XMPP: sailus@retiisi.org.uk