[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>

3 files changed, 47 insertions, 3 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>
diff --git a/include/linux/videodev2.h b/include/linux/videodev2.h
index fca24cc50436..a5359c6e7577 100644
--- a/include/linux/videodev2.h
+++ b/include/linux/videodev2.h
@@ -2006,6 +2006,7 @@ struct v4l2_streamparm {
 #define V4L2_EVENT_VSYNC                        1
 #define V4L2_EVENT_EOS                          2
 #define V4L2_EVENT_CTRL                         3
+#define V4L2_EVENT_FRAME_SYNC                   4
 #define V4L2_EVENT_PRIVATE_START                0x08000000
 
 /* Payload for V4L2_EVENT_VSYNC */
@@ -2032,12 +2033,17 @@ struct v4l2_event_ctrl {
         __s32 default_value;
 };
 
+struct v4l2_event_frame_sync {
+        __u32 frame_sequence;
+};
+
 struct v4l2_event {
         __u32                           type;
         union {
-                struct v4l2_event_vsync vsync;
-                struct v4l2_event_ctrl  ctrl;
-                __u8                    data[64];
+                struct v4l2_event_vsync         vsync;
+                struct v4l2_event_ctrl          ctrl;
+                struct v4l2_event_frame_sync    frame_sync;
+                __u8                            data[64];
         } u;
         __u32                           pending;
         __u32                           sequence;