diff options
Diffstat (limited to 'Documentation/video4linux/v4l2-framework.txt')
| -rw-r--r-- | Documentation/video4linux/v4l2-framework.txt | 28 |
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. |