[media] v4l: subdev: Events support

Provide v4l2_subdevs with v4l2_event support. Subdev drivers only need very
little to support events.

Signed-off-by: Sakari Ailus <sakari.ailus@iki.fi>
Signed-off-by: David Cohen <dacohen@gmail.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

1 files changed, 18 insertions, 0 deletions

diff --git a/Documentation/video4linux/v4l2-framework.txt b/Documentation/video4linux/v4l2-framework.txt
index 1feecfc59c3d..eb8479565dc4 100644
--- a/Documentation/video4linux/v4l2-framework.txt
+++ b/Documentation/video4linux/v4l2-framework.txt
@@ -350,6 +350,24 @@ VIDIOC_TRY_EXT_CTRLS
         controls can be also be accessed through one (or several) V4L2 device
         nodes.
 
+VIDIOC_DQEVENT
+VIDIOC_SUBSCRIBE_EVENT
+VIDIOC_UNSUBSCRIBE_EVENT
+
+        The events ioctls are identical to the ones defined in V4L2. They
+        behave identically, with the only exception that they deal only with
+        events generated by the sub-device. Depending on the driver, those
+        events can also be reported by one (or several) V4L2 device nodes.
+
+        Sub-device drivers that want to use events need to set the
+        V4L2_SUBDEV_USES_EVENTS v4l2_subdev::flags and initialize
+        v4l2_subdev::nevents to events queue depth before registering the
+        sub-device. After registration events can be queued as usual on the
+        v4l2_subdev::devnode device node.
+
+        To properly support events, the poll() file operation is also
+        implemented.
+
 
 I2C sub-device drivers
 ----------------------