media: v4l2-ctrl: Add decoder conceal color control

Add decoder v4l2 control to set conceal color.

Signed-off-by: Stanimir Varbanov <stanimir.varbanov@linaro.org>
Reviewed-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

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

@@ -674,6 +674,39 @@ enum v4l2_mpeg_video_frame_skip_mode -
     is currently displayed (decoded). This value is reset to 0 whenever
     the decoder is started.
 
+``V4L2_CID_MPEG_VIDEO_DEC_CONCEAL_COLOR (integer64)``
+    This control sets the conceal color in YUV color space. It describes
+    the client preference of the error conceal color in case of an error
+    where the reference frame is missing. The decoder should fill the
+    reference buffer with the preferred color and use it for future
+    decoding. The control is using 16 bits per channel.
+    Applicable to decoders.
+
+.. flat-table::
+    :header-rows:  0
+    :stub-columns: 0
+
+    * -
+      - 8bit  format
+      - 10bit format
+      - 12bit format
+    * - Y luminance
+      - Bit 0:7
+      - Bit 0:9
+      - Bit 0:11
+    * - Cb chrominance
+      - Bit 16:23
+      - Bit 16:25
+      - Bit 16:27
+    * - Cr chrominance
+      - Bit 32:39
+      - Bit 32:41
+      - Bit 32:43
+    * - Must be zero
+      - Bit 48:63
+      - Bit 48:63
+      - Bit 48:63
+
 ``V4L2_CID_MPEG_VIDEO_DECODER_SLICE_INTERFACE (boolean)``
     If enabled the decoder expects to receive a single slice per buffer,
     otherwise the decoder expects a single frame in per buffer.