media: videodev2.h: add V4L2_CTRL_FLAG_DYNAMIC_ARRAY

Add a new flag that indicates that this control is a dynamically sized
array. Also document this flag.

Currently dynamically sized arrays are limited to one dimensional arrays,
but that might change in the future if there is a need for it.

The initial use-case of dynamic arrays are stateless codecs. A frame
can be divided in many slices, so you want to provide an array containing
slice information for each slice. Typically the number of slices is small,
but the standard allow for hundreds or thousands of slices. Dynamic arrays
are a good solution since sizing the array for the worst case would waste
substantial amounts of memory.

Acked-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Tested-by: Benjamin Gaignard <benjamin.gaignard@collabora.com>
Tested-by: Jernej Skrabec <jernej.skrabec@gmail.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

diff --git a/Documentation/userspace-api/media/v4l/vidioc-queryctrl.rst b/Documentation/userspace-api/media/v4l/vidioc-queryctrl.rst
index 88f630252d987b7fc2b0ada9d424bc86dd0a3b79..a20dfa2a933b89c854bfe213b35e83e78d9dccff 100644 (file)
--- a/Documentation/userspace-api/media/v4l/vidioc-queryctrl.rst
+++ b/Documentation/userspace-api/media/v4l/vidioc-queryctrl.rst
@@ -625,6 +625,14 @@ See also the examples in :ref:`control`.
        ``V4L2_CTRL_FLAG_GRABBED`` flag when buffers are allocated or
        streaming is in progress since most drivers do not support changing
        the format in that case.
+    * - ``V4L2_CTRL_FLAG_DYNAMIC_ARRAY``
+      - 0x0800
+      - This control is a dynamically sized 1-dimensional array. It
+        behaves the same as a regular array, except that the number
+       of elements as reported by the ``elems`` field is between 1 and
+       ``dims[0]``. So setting the control with a differently sized
+       array will change the ``elems`` field when the control is
+       queried afterwards.
 
 Return Value
 ============

diff --git a/Documentation/userspace-api/media/videodev2.h.rst.exceptions b/Documentation/userspace-api/media/videodev2.h.rst.exceptions
index 9cbb7a0c354a54d57b4b4c15a1461284df03087d..0b91200776f8329e19fe9ecb6308c8d908395666 100644 (file)
--- a/Documentation/userspace-api/media/videodev2.h.rst.exceptions
+++ b/Documentation/userspace-api/media/videodev2.h.rst.exceptions
@@ -379,6 +379,7 @@ replace define V4L2_CTRL_FLAG_VOLATILE control-flags
 replace define V4L2_CTRL_FLAG_HAS_PAYLOAD control-flags
 replace define V4L2_CTRL_FLAG_EXECUTE_ON_WRITE control-flags
 replace define V4L2_CTRL_FLAG_MODIFY_LAYOUT control-flags
+replace define V4L2_CTRL_FLAG_DYNAMIC_ARRAY control-flags
 
 replace define V4L2_CTRL_FLAG_NEXT_CTRL control
 replace define V4L2_CTRL_FLAG_NEXT_COMPOUND control

diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
index e32b9e25258d72679f3c14337cc66c8f58ba06c3..87ebc6baafb6c4c61d6e3fc0e8ed62111b33a165 100644 (file)
--- a/include/uapi/linux/videodev2.h
+++ b/include/uapi/linux/videodev2.h
@@ -1914,6 +1914,7 @@ struct v4l2_querymenu {
 #define V4L2_CTRL_FLAG_HAS_PAYLOAD     0x0100
 #define V4L2_CTRL_FLAG_EXECUTE_ON_WRITE        0x0200
 #define V4L2_CTRL_FLAG_MODIFY_LAYOUT   0x0400
+#define V4L2_CTRL_FLAG_DYNAMIC_ARRAY   0x0800
 
 /*  Query flags, to be ORed with the control ID */
 #define V4L2_CTRL_FLAG_NEXT_CTRL       0x80000000