[PATCH 1/4] v4l: Define video buffer flags for timestamp types

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



Define video buffer flags for different timestamp types. Everything up to
now have used either realtime clock or monotonic clock, without a way to
tell which clock the timestamp was taken from.

Signed-off-by: Sakari Ailus <sakari.ailus@xxxxxx>
Acked-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
---
 Documentation/DocBook/media/v4l/io.xml |   25 +++++++++++++++++++++++++
 include/uapi/linux/videodev2.h         |    4 ++++
 2 files changed, 29 insertions(+), 0 deletions(-)

diff --git a/Documentation/DocBook/media/v4l/io.xml b/Documentation/DocBook/media/v4l/io.xml
index 7e2f3d7..d598f2c 100644
--- a/Documentation/DocBook/media/v4l/io.xml
+++ b/Documentation/DocBook/media/v4l/io.xml
@@ -938,6 +938,31 @@ Typically applications shall use this flag for output buffers if the data
 in this buffer has not been created by the CPU but by some DMA-capable unit,
 in which case caches have not been used.</entry>
 	  </row>
+	  <row>
+	    <entry><constant>V4L2_BUF_FLAG_TIMESTAMP_MASK</constant></entry>
+	    <entry>0xe000</entry>
+	    <entry>Mask for timestamp types below. To test the
+	    timestamp type, mask out bits not belonging to timestamp
+	    type by performing a logical and operation with buffer
+	    flags and timestamp mask.</tt> </entry>
+	  </row>
+	  <row>
+	    <entry><constant>V4L2_BUF_FLAG_TIMESTAMP_UNKNOWN</constant></entry>
+	    <entry>0x0000</entry>
+	    <entry>Unknown timestamp type. This type is used by
+	    drivers before Linux 3.8 and may be either monotonic (see
+	    below) or realtime. Monotonic clock has been favoured in
+	    embedded systems whereas most of the drivers use the
+	    realtime clock.</entry>
+	  </row>
+	  <row>
+	    <entry><constant>V4L2_BUF_FLAG_TIMESTAMP_MONOTONIC</constant></entry>
+	    <entry>0x2000</entry>
+	    <entry>The buffer timestamp has been taken from the
+	    <constant>CLOCK_MONOTONIC</constant> clock. To access the
+	    same clock outside V4L2, use <tt>clock_gettime(2)</tt>
+	    .</entry>
+	  </row>
 	</tbody>
       </tgroup>
     </table>
diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
index 2fff7ff..410ea9f 100644
--- a/include/uapi/linux/videodev2.h
+++ b/include/uapi/linux/videodev2.h
@@ -686,6 +686,10 @@ struct v4l2_buffer {
 /* Cache handling flags */
 #define V4L2_BUF_FLAG_NO_CACHE_INVALIDATE	0x0800
 #define V4L2_BUF_FLAG_NO_CACHE_CLEAN		0x1000
+/* Timestamp type */
+#define V4L2_BUF_FLAG_TIMESTAMP_MASK		0xe000
+#define V4L2_BUF_FLAG_TIMESTAMP_UNKNOWN		0x0000
+#define V4L2_BUF_FLAG_TIMESTAMP_MONOTONIC	0x2000
 
 /*
  *	O V E R L A Y   P R E V I E W
-- 
1.7.2.5

--
To unsubscribe from this list: send the line "unsubscribe linux-media" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html


[Index of Archives]     [Linux Input]     [Video for Linux]     [Gstreamer Embedded]     [Mplayer Users]     [Linux USB Devel]     [Linux Audio Users]     [Linux Kernel]     [Linux SCSI]     [Yosemite Backpacking]
  Powered by Linux