Based on kernel version 3.0.4. Page generated on 2011-10-03 22:07 EST.
1 <title>Event Interface</title> 2 3 <para>The V4L2 event interface provides means for user to get 4 immediately notified on certain conditions taking place on a device. 5 This might include start of frame or loss of signal events, for 6 example. 7 </para> 8 9 <para>To receive events, the events the user is interested in first must 10 be subscribed using the &VIDIOC-SUBSCRIBE-EVENT; ioctl. Once an event is 11 subscribed, the events of subscribed types are dequeueable using the 12 &VIDIOC-DQEVENT; ioctl. Events may be unsubscribed using 13 VIDIOC_UNSUBSCRIBE_EVENT ioctl. The special event type V4L2_EVENT_ALL may 14 be used to unsubscribe all the events the driver supports.</para> 15 16 <para>The event subscriptions and event queues are specific to file 17 handles. Subscribing an event on one file handle does not affect 18 other file handles. 19 </para> 20 21 <para>The information on dequeueable events is obtained by using select or 22 poll system calls on video devices. The V4L2 events use POLLPRI events on 23 poll system call and exceptions on select system call. </para> 24 25 <!-- 26 Local Variables: 27 mode: sgml 28 sgml-parent-document: "v4l2.sgml" 29 indent-tabs-mode: nil 30 End: 31 -->
