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-rw-r--r--Documentation/video4linux/v4l2-framework.txt28
1 files changed, 21 insertions, 7 deletions
diff --git a/Documentation/video4linux/v4l2-framework.txt b/Documentation/video4linux/v4l2-framework.txt
index e3dfc268d9c1..369d4bc87828 100644
--- a/Documentation/video4linux/v4l2-framework.txt
+++ b/Documentation/video4linux/v4l2-framework.txt
@@ -945,21 +945,35 @@ fast.
Useful functions:
-- v4l2_event_queue()
+void v4l2_event_queue(struct video_device *vdev, const struct v4l2_event *ev)
Queue events to video device. The driver's only responsibility is to fill
in the type and the data fields. The other fields will be filled in by
V4L2.
-- v4l2_event_subscribe()
+int v4l2_event_subscribe(struct v4l2_fh *fh,
+ struct v4l2_event_subscription *sub, unsigned elems,
+ const struct v4l2_subscribed_event_ops *ops)
The video_device->ioctl_ops->vidioc_subscribe_event must check the driver
is able to produce events with specified event id. Then it calls
- v4l2_event_subscribe() to subscribe the event. The last argument is the
- size of the event queue for this event. If it is 0, then the framework
- will fill in a default value (this depends on the event type).
+ v4l2_event_subscribe() to subscribe the event.
-- v4l2_event_unsubscribe()
+ The elems argument is the size of the event queue for this event. If it is 0,
+ then the framework will fill in a default value (this depends on the event
+ type).
+
+ The ops argument allows the driver to specify a number of callbacks:
+ * add: called when a new listener gets added (subscribing to the same
+ event twice will only cause this callback to get called once)
+ * del: called when a listener stops listening
+ * replace: replace event 'old' with event 'new'.
+ * merge: merge event 'old' into event 'new'.
+ All 4 callbacks are optional, if you don't want to specify any callbacks
+ the ops argument itself maybe NULL.
+
+int v4l2_event_unsubscribe(struct v4l2_fh *fh,
+ struct v4l2_event_subscription *sub)
vidioc_unsubscribe_event in struct v4l2_ioctl_ops. A driver may use
v4l2_event_unsubscribe() directly unless it wants to be involved in
@@ -968,7 +982,7 @@ Useful functions:
The special type V4L2_EVENT_ALL may be used to unsubscribe all events. The
drivers may want to handle this in a special way.
-- v4l2_event_pending()
+int v4l2_event_pending(struct v4l2_fh *fh)
Returns the number of pending events. Useful when implementing poll.

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