[PATCH v8 05/13] [media] v4l: add 'unordered' flag to format description ioctl

[Gustavo Padovan]

From: Gustavo Padovan <gustavo.padovan@xxxxxxxxxxxxx>

For explicit synchronization it important for userspace to know if the
format being used by the driver can deliver the buffers back to userspace
in the same order they were queued with QBUF.

Ordered streams fits nicely in a pipeline with DRM for example, where
ordered buffer are expected.

v2	- Improve documentation (Hans)

Signed-off-by: Gustavo Padovan <gustavo.padovan@xxxxxxxxxxxxx>
---
 Documentation/media/uapi/v4l/vidioc-enum-fmt.rst | 7 +++++++
 include/uapi/linux/videodev2.h                   | 1 +
 2 files changed, 8 insertions(+)

diff --git a/Documentation/media/uapi/v4l/vidioc-enum-fmt.rst b/Documentation/media/uapi/v4l/vidioc-enum-fmt.rst
index 019c513df217..df8e039b9ac2 100644
--- a/Documentation/media/uapi/v4l/vidioc-enum-fmt.rst
+++ b/Documentation/media/uapi/v4l/vidioc-enum-fmt.rst
@@ -116,6 +116,13 @@ one until ``EINVAL`` is returned.
       - This format is not native to the device but emulated through
 	software (usually libv4l2), where possible try to use a native
 	format instead for better performance.
+    * - ``V4L2_FMT_FLAG_UNORDERED``
+      - 0x0004
+      - This format doesn't guarantee ordered buffer handling. I.e. the order
+	in which buffers are dequeued with
+	:ref:`VIDIOC_DQBUF <VIDIOC_QBUF>` may be different
+	from the order in which they were queued with
+	:ref:`VIDIOC_QBUF <VIDIOC_QBUF>`.
 
 
 Return Value
diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
index 982718965180..58894cfe9479 100644
--- a/include/uapi/linux/videodev2.h
+++ b/include/uapi/linux/videodev2.h
@@ -716,6 +716,7 @@ struct v4l2_fmtdesc {
 
 #define V4L2_FMT_FLAG_COMPRESSED 0x0001
 #define V4L2_FMT_FLAG_EMULATED   0x0002
+#define V4L2_FMT_FLAG_UNORDERED  0x0004
 
 	/* Frame Size and frame rate enumeration */
 /*
-- 
2.14.3