[PATCH/RFC v9 15/19] Documentation: leds: Add description of v4l2-flash sub-device

From: Jacek Anaszewski
Date: Wed Dec 03 2014 - 11:08:59 EST

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>
Acked-by: Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx>
Cc: Bryan Wu <cooloney@xxxxxxxxx>
Cc: Richard Purdie <rpurdie@xxxxxxxxx>
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 82e58b1..bc3855b 100644
--- a/Documentation/leds/leds-class-flash.txt
+++ b/Documentation/leds/leds-class-flash.txt
@@ -48,3 +48,16 @@ Following sysfs attributes are exposed for controlling flash led devices:
upper limit

Flash faults are cleared by reading the attribute.
+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>).
+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.
+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.

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