Re: [PATCH v2 09/11] Documentation: leds: Add description of v4l2-flash sub-device
From: Sakari Ailus <sakari.ailus@iki.fi>
Date: 2015-03-28 23:35:32
Also in:
linux-leds, linux-media
Hi Jacek, On Fri, Mar 27, 2015 at 02:49:43PM +0100, Jacek Anaszewski wrote:
quoted hunk ↗ jump to hunk
This patch extends LED Flash class documention by the description of interactions with v4l2-flash sub-device. Signed-off-by: Jacek Anaszewski <redacted> Acked-by: Kyungmin Park <kyungmin.park@samsung.com> Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com> Cc: Bryan Wu <redacted> Cc: Richard Purdie <redacted> --- 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