From 871480933a1c28f8a9fed4c4d34d06c439a7a422 Mon Sep 17 00:00:00 2001 From: Srikant Patnaik Date: Sun, 11 Jan 2015 12:28:04 +0530 Subject: Moved, renamed, and deleted files The original directory structure was scattered and unorganized. Changes are basically to make it look like kernel structure. --- .../DocBook/media/v4l/vidioc-subscribe-event.xml | 206 +++++++++++++++++++++ 1 file changed, 206 insertions(+) create mode 100644 Documentation/DocBook/media/v4l/vidioc-subscribe-event.xml (limited to 'Documentation/DocBook/media/v4l/vidioc-subscribe-event.xml') diff --git a/Documentation/DocBook/media/v4l/vidioc-subscribe-event.xml b/Documentation/DocBook/media/v4l/vidioc-subscribe-event.xml new file mode 100644 index 00000000..5c70b616 --- /dev/null +++ b/Documentation/DocBook/media/v4l/vidioc-subscribe-event.xml @@ -0,0 +1,206 @@ + + + ioctl VIDIOC_SUBSCRIBE_EVENT, VIDIOC_UNSUBSCRIBE_EVENT + &manvol; + + + + VIDIOC_SUBSCRIBE_EVENT, VIDIOC_UNSUBSCRIBE_EVENT + Subscribe or unsubscribe event + + + + + + int ioctl + int fd + int request + struct v4l2_event_subscription +*argp + + + + + + Arguments + + + + fd + + &fd; + + + + request + + VIDIOC_SUBSCRIBE_EVENT, VIDIOC_UNSUBSCRIBE_EVENT + + + + argp + + + + + + + + + Description + + Subscribe or unsubscribe V4L2 event. Subscribed events are + dequeued by using the &VIDIOC-DQEVENT; ioctl. + + + struct <structname>v4l2_event_subscription</structname> + + &cs-str; + + + __u32 + type + Type of the event. + + + __u32 + id + ID of the event source. If there is no ID associated with + the event source, then set this to 0. Whether or not an event + needs an ID depends on the event type. + + + __u32 + flags + Event flags, see . + + + __u32 + reserved[5] + Reserved for future extensions. Drivers and applications + must set the array to zero. + + + +
+ + + Event Types + + &cs-def; + + + V4L2_EVENT_ALL + 0 + All events. V4L2_EVENT_ALL is valid only for + VIDIOC_UNSUBSCRIBE_EVENT for unsubscribing all events at once. + + + + V4L2_EVENT_VSYNC + 1 + This event is triggered on the vertical sync. + This event has a &v4l2-event-vsync; associated with it. + + + + V4L2_EVENT_EOS + 2 + This event is triggered when the end of a stream is reached. + This is typically used with MPEG decoders to report to the application + when the last of the MPEG stream has been decoded. + + + + V4L2_EVENT_CTRL + 3 + This event requires that the id + matches the control ID from which you want to receive events. + This event is triggered if the control's value changes, if a + button control is pressed or if the control's flags change. + This event has a &v4l2-event-ctrl; associated with it. This struct + contains much of the same information as &v4l2-queryctrl; and + &v4l2-control;. + + If the event is generated due to a call to &VIDIOC-S-CTRL; or + &VIDIOC-S-EXT-CTRLS;, then the event will not be sent to + the file handle that called the ioctl function. This prevents + nasty feedback loops. If you do want to get the + event, then set the V4L2_EVENT_SUB_FL_ALLOW_FEEDBACK + flag. + + + This event type will ensure that no information is lost when + more events are raised than there is room internally. In that + case the &v4l2-event-ctrl; of the second-oldest event is kept, + but the changes field of the + second-oldest event is ORed with the changes + field of the oldest event. + + + + V4L2_EVENT_FRAME_SYNC + 4 + + Triggered immediately when the reception of a + frame has begun. This event has a + &v4l2-event-frame-sync; associated with it. + + If the hardware needs to be stopped in the case of a + buffer underrun it might not be able to generate this event. + In such cases the frame_sequence + field in &v4l2-event-frame-sync; will not be incremented. This + causes two consecutive frame sequence numbers to have n times + frame interval in between them. + + + + V4L2_EVENT_PRIVATE_START + 0x08000000 + Base event number for driver-private events. + + + +
+ + + Event Flags + + &cs-def; + + + V4L2_EVENT_SUB_FL_SEND_INITIAL + 0x0001 + When this event is subscribed an initial event will be sent + containing the current status. This only makes sense for events + that are triggered by a status change such as V4L2_EVENT_CTRL. + Other events will ignore this flag. + + + V4L2_EVENT_SUB_FL_ALLOW_FEEDBACK + 0x0002 + If set, then events directly caused by an ioctl will also be sent to + the filehandle that called that ioctl. For example, changing a control using + &VIDIOC-S-CTRL; will cause a V4L2_EVENT_CTRL to be sent back to that same + filehandle. Normally such events are suppressed to prevent feedback loops + where an application changes a control to a one value and then another, and + then receives an event telling it that that control has changed to the first + value. + + Since it can't tell whether that event was caused by another application + or by the &VIDIOC-S-CTRL; call it is hard to decide whether to set the + control to the value in the event, or ignore it. + + Think carefully when you set this flag so you won't get into situations + like that. + + + + +
+ + + + &return-value; + + -- cgit