Le mercredi 05 mai 2021 à 16:18 +0100, John Cox a écrit :

quoted

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>
---
.../userspace-api/media/drivers/hantro.rst    | 19 +++++++++++++++++++
.../userspace-api/media/drivers/index.rst     |  1 +
include/media/hevc-ctrls.h                    | 13 +++++++++++++
3 files changed, 33 insertions(+)
create mode 100644 Documentation/userspace-api/media/drivers/hantro.rst

diff --git a/Documentation/userspace-api/media/drivers/hantro.rst

b/Documentation/userspace-api/media/drivers/hantro.rst
new file mode 100644
index 000000000000..cd9754b4e005

--- /dev/null
+++ b/Documentation/userspace-api/media/drivers/hantro.rst

@@ -0,0 +1,19 @@
+.. 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).

What happens if it is a dependant_slice_segement or
output_flag_present_flag?  Those flags are all dependant on
dependant_slice_segement being false.  I'm guessing 0 but it maybe
should be documented.

Zero indeed.

Likewise if output_flag_present_flag is false pic_output_flag will not
be coded, so maybe express it as "after slice_type" rather than "before
pic_output_flag"?

Should work too.

Regards

John Cox

quoted

+.. note::
+
+        This control is not yet part of the public kernel API and
+        it is expected to change.

diff --git a/Documentation/userspace-api/media/drivers/index.rst

b/Documentation/userspace-api/media/drivers/index.rst
index 1a9038f5f9fa..12e3c512d718 100644

--- a/Documentation/userspace-api/media/drivers/index.rst
+++ b/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

diff --git a/include/media/hevc-ctrls.h b/include/media/hevc-ctrls.h
index 8e0109eea454..b713eeed1915 100644
--- a/include/media/hevc-ctrls.h
+++ b/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