[media] v4l: events: Define V4L2_EVENT_FRAME_SYNC

Define a frame sync event to tell user space when the reception of a frame
starts.

Signed-off-by: Sakari Ailus <sakari.ailus@iki.fi>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

2 files changed, 38 insertions, 0 deletions

diff --git a/Documentation/DocBook/media/v4l/vidioc-dqevent.xml b/Documentation/DocBook/media/v4l/vidioc-dqevent.xml
index 5200b6874654..e8714aa16433 100644
--- a/Documentation/DocBook/media/v4l/vidioc-dqevent.xml
+++ b/Documentation/DocBook/media/v4l/vidioc-dqevent.xml
@@ -88,6 +88,12 @@
           </row>
           <row>
             <entry></entry>
+            <entry>&v4l2-event-frame-sync;</entry>
+            <entry><structfield>frame</structfield></entry>
+            <entry>Event data for event V4L2_EVENT_FRAME_SYNC.</entry>
+          </row>
+          <row>
+            <entry></entry>
             <entry>__u8</entry>
             <entry><structfield>data</structfield>[64]</entry>
             <entry>Event data. Defined by the event type. The union
@@ -220,6 +226,22 @@
       </tgroup>
     </table>
 
+    <table frame="none" pgwide="1" id="v4l2-event-frame-sync">
+      <title>struct <structname>v4l2_event_frame_sync</structname></title>
+      <tgroup cols="3">
+        &cs-str;
+        <tbody valign="top">
+          <row>
+            <entry>__u32</entry>
+            <entry><structfield>frame_sequence</structfield></entry>
+            <entry>
+              The sequence number of the frame being received.
+            </entry>
+          </row>
+        </tbody>
+      </tgroup>
+    </table>
+
     <table pgwide="1" frame="none" id="changes-flags">
       <title>Changes</title>
       <tgroup cols="3">
diff --git a/Documentation/DocBook/media/v4l/vidioc-subscribe-event.xml b/Documentation/DocBook/media/v4l/vidioc-subscribe-event.xml
index 275be9689d88..5c70b616d818 100644
--- a/Documentation/DocBook/media/v4l/vidioc-subscribe-event.xml
+++ b/Documentation/DocBook/media/v4l/vidioc-subscribe-event.xml
@@ -139,6 +139,22 @@
             </entry>
           </row>
           <row>
+            <entry><constant>V4L2_EVENT_FRAME_SYNC</constant></entry>
+            <entry>4</entry>
+            <entry>
+              <para>Triggered immediately when the reception of a
+              frame has begun. This event has a
+              &v4l2-event-frame-sync; associated with it.</para>
+
+              <para>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 <structfield>frame_sequence</structfield>
+              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.</para>
+            </entry>
+          </row>
+          <row>
             <entry><constant>V4L2_EVENT_PRIVATE_START</constant></entry>
             <entry>0x08000000</entry>
             <entry>Base event number for driver-private events.</entry>