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diff --git a/Documentation/DocBook/media/v4l/dev-event.xml b/Documentation/DocBook/media/v4l/dev-event.xml deleted file mode 100644 index 19f4becfae34..000000000000 --- a/Documentation/DocBook/media/v4l/dev-event.xml +++ /dev/null @@ -1,43 +0,0 @@ - <title>Event Interface</title> - - <para>The V4L2 event interface provides a means for a user to get - immediately notified on certain conditions taking place on a device. - This might include start of frame or loss of signal events, for - example. Changes in the value or state of a V4L2 control can also be - reported through events. - </para> - - <para>To receive events, the events the user is interested in first must - be subscribed using the &VIDIOC-SUBSCRIBE-EVENT; ioctl. Once an event is - subscribed, the events of subscribed types are dequeueable using the - &VIDIOC-DQEVENT; ioctl. Events may be unsubscribed using - VIDIOC_UNSUBSCRIBE_EVENT ioctl. The special event type V4L2_EVENT_ALL may - be used to unsubscribe all the events the driver supports.</para> - - <para>The event subscriptions and event queues are specific to file - handles. Subscribing an event on one file handle does not affect - other file handles.</para> - - <para>The information on dequeueable events is obtained by using select or - poll system calls on video devices. The V4L2 events use POLLPRI events on - poll system call and exceptions on select system call.</para> - - <para>Starting with kernel 3.1 certain guarantees can be given with - regards to events:<orderedlist> - <listitem> - <para>Each subscribed event has its own internal dedicated event queue. -This means that flooding of one event type will not interfere with other -event types.</para> - </listitem> - <listitem> - <para>If the internal event queue for a particular subscribed event -becomes full, then the oldest event in that queue will be dropped.</para> - </listitem> - <listitem> - <para>Where applicable, certain event types can ensure that the payload -of the oldest event that is about to be dropped will be merged with the payload -of the next oldest event. Thus ensuring that no information is lost, but only an -intermediate step leading up to that information. See the documentation for the -event you want to subscribe to whether this is applicable for that event or not.</para> - </listitem> - </orderedlist></para> |