media: uapi: HEVC: Define V4L2_CID_STATELESS_HEVC_SLICE_PARAMS as a dynamic array

Make explicit that V4L2_CID_STATELESS_HEVC_SLICE_PARAMS control is
a dynamic array control type.
Some drivers may be able to receive multiple slices in one control
to improve decoding performance.
Signed-off-by: Benjamin Gaignard <benjamin.gaignard@collabora.com>
Reviewed-by: Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst

@@ -2986,6 +2986,8 @@ enum v4l2_mpeg_video_hevc_size_of_length_field -
     These bitstream parameters are defined according to :ref:`hevc`.
     They are described in section 7.4.7 "General slice segment header
     semantics" of the specification.
+    This control is a dynamically sized 1-dimensional array,
+    V4L2_CTRL_FLAG_DYNAMIC_ARRAY flag must be set when using it.
 
 .. c:type:: v4l2_ctrl_hevc_slice_params
 

drivers/media/v4l2-core/v4l2-ctrls-defs.c

@@ -1510,6 +1510,7 @@ void v4l2_ctrl_fill(u32 id, const char **name, enum v4l2_ctrl_type *type,
 		break;
 	case V4L2_CID_STATELESS_HEVC_SLICE_PARAMS:
 		*type = V4L2_CTRL_TYPE_HEVC_SLICE_PARAMS;
+		*flags |= V4L2_CTRL_FLAG_DYNAMIC_ARRAY;
 		break;
 	case V4L2_CID_STATELESS_HEVC_SCALING_MATRIX:
 		*type = V4L2_CTRL_TYPE_HEVC_SCALING_MATRIX;

drivers/staging/media/sunxi/cedrus/cedrus.c

@@ -178,6 +178,8 @@ static const struct cedrus_control cedrus_controls[] = {
 	{
 		.cfg = {
 			.id	= V4L2_CID_STATELESS_HEVC_SLICE_PARAMS,
+			/* The driver can only handle 1 entry per slice for now */
+			.dims   = { 1 },
 		},
 		.codec		= CEDRUS_CODEC_H265,
 	},

include/media/hevc-ctrls.h

@@ -314,6 +314,9 @@ struct v4l2_hevc_pred_weight_table {
 /**
  * struct v4l2_ctrl_hevc_slice_params - HEVC slice parameters
  *
+ * This control is a dynamically sized 1-dimensional array,
+ * V4L2_CTRL_FLAG_DYNAMIC_ARRAY flag must be set when using it.
+ *
  * @bit_size: size (in bits) of the current slice data
  * @data_bit_offset: offset (in bits) to the video data in the current slice data
  * @nal_unit_type: specifies the coding type of the slice (B, P or I)