media: uapi: Add a control for HANTRO driver

The HEVC HANTRO driver needs to know the number of bits to skip at
the beginning of the slice header.
That is a hardware specific requirement so create a dedicated control
for this purpose.
Signed-off-by: Benjamin Gaignard <benjamin.gaignard@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

Documentation/userspace-api/media/drivers/hantro.rst

+.. SPDX-License-Identifier: GPL-2.0
+
+Hantro video decoder driver
+===========================
+
+The Hantro video decoder driver implements the following driver-specific controls:
+
+``V4L2_CID_HANTRO_HEVC_SLICE_HEADER_SKIP (integer)``
+    Specifies to Hantro HEVC video decoder driver the number of data (in bits) to
+    skip in the slice segment header.
+    If non-IDR, the bits to be skipped go from syntax element "pic_output_flag"
+    to before syntax element "slice_temporal_mvp_enabled_flag".
+    If IDR, the skipped bits are just "pic_output_flag"
+    (separate_colour_plane_flag is not supported).
+
+.. note::
+
+        This control is not yet part of the public kernel API and
+        it is expected to change.

Documentation/userspace-api/media/drivers/index.rst

@@ -33,6 +33,7 @@ For more details see the file COPYING in the source distribution of Linux.
 
 	ccs
 	cx2341x-uapi
+        hantro
 	imx-uapi
 	max2175
 	meye-uapi

include/media/hevc-ctrls.h

@@ -224,4 +224,17 @@ struct v4l2_ctrl_hevc_decode_params {
 	__u64	flags;
 };
 
+/*  MPEG-class control IDs specific to the Hantro driver as defined by V4L2 */
+#define V4L2_CID_CODEC_HANTRO_BASE				(V4L2_CTRL_CLASS_CODEC | 0x1200)
+/*
+ * V4L2_CID_HANTRO_HEVC_SLICE_HEADER_SKIP -
+ * the number of data (in bits) to skip in the
+ * slice segment header.
+ * If non-IDR, the bits to be skipped go from syntax element "pic_output_flag"
+ * to before syntax element "slice_temporal_mvp_enabled_flag".
+ * If IDR, the skipped bits are just "pic_output_flag"
+ * (separate_colour_plane_flag is not supported).
+ */
+#define V4L2_CID_HANTRO_HEVC_SLICE_HEADER_SKIP	(V4L2_CID_CODEC_HANTRO_BASE + 0)
+
 #endif