linux-kernel - [PATCH] media: uapi: HEVC: Add num_delta_pocs_of_ref_rps

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Message-Id: <20230418160717.743517-1-benjamin.gaignard@collabora.com>
Date:   Tue, 18 Apr 2023 18:07:17 +0200
From:   Benjamin Gaignard <benjamin.gaignard@...labora.com>
To:     mchehab@...nel.org, hverkuil-cisco@...all.nl,
        nicolas.dufresne@...labora.com
Cc:     linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel@...labora.com,
        Benjamin Gaignard <benjamin.gaignard@...labora.com>
Subject: [PATCH] media: uapi: HEVC: Add num_delta_pocs_of_ref_rps_idx field

Some drivers firmwares parse by themselves slice header and need
num_delta_pocs_of_ref_rps_idx value to parse slice header
short_term_ref_pic_set().
Use one of the 4 reserved bytes to store this value without
changing the v4l2_ctrl_hevc_decode_params structure size and padding.

This value also exist in DXVA API.

Signed-off-by: Benjamin Gaignard <benjamin.gaignard@...labora.com>
---
 .../userspace-api/media/v4l/ext-ctrls-codec-stateless.rst  | 7 +++++++
 include/uapi/linux/v4l2-controls.h                         | 6 +++++-
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/Documentation/userspace-api/media/v4l/ext-ctrls-codec-stateless.rst b/Documentation/userspace-api/media/v4l/ext-ctrls-codec-stateless.rst
index 3d8411acd5b8..92ce3e126929 100644
--- a/Documentation/userspace-api/media/v4l/ext-ctrls-codec-stateless.rst
+++ b/Documentation/userspace-api/media/v4l/ext-ctrls-codec-stateless.rst
@@ -2923,6 +2923,13 @@ This structure contains all loop filter related parameters. See sections
       - ``poc_lt_curr[V4L2_HEVC_DPB_ENTRIES_NUM_MAX]``
       - PocLtCurr as described in section 8.3.2 "Decoding process for reference
         picture set": provides the index of the long term references in DPB array.
+    * - __u8
+      - ``num_delta_pocs_of_ref_rps_idx``
+      - When the short_term_ref_pic_set_sps_flag in the slice header is equal to 0,
+        it is the same than derived value NumDeltaPocs[RefRpsIdx]. It can be used to parse
+        the RPS data in slice headers instead of skipping it with @short_term_ref_pic_set_size.
+        When the value of short_term_ref_pic_set_sps_flag in the slice header is
+        equal to 1, num_delta_pocs_of_ref_rps_idx shall be set to 0.
     * - struct :c:type:`v4l2_hevc_dpb_entry`
       - ``dpb[V4L2_HEVC_DPB_ENTRIES_NUM_MAX]``
       - The decoded picture buffer, for meta-data about reference frames.
diff --git a/include/uapi/linux/v4l2-controls.h b/include/uapi/linux/v4l2-controls.h
index 5e80daa4ffe0..7bf59a87a1bf 100644
--- a/include/uapi/linux/v4l2-controls.h
+++ b/include/uapi/linux/v4l2-controls.h
@@ -2385,6 +2385,9 @@ struct v4l2_ctrl_hevc_slice_params {
  * @poc_st_curr_after: provides the index of the short term after references
  *		       in DPB array
  * @poc_lt_curr: provides the index of the long term references in DPB array
+ * @num_delta_pocs_of_ref_rps_idx: same as the derived value NumDeltaPocs[RefRpsIdx],
+ *				   can be used to parse the RPS data in slice headers
+ *				   instead of skipping it with @short_term_ref_pic_set_size.
  * @reserved: padding field. Should be zeroed by applications.
  * @dpb: the decoded picture buffer, for meta-data about reference frames
  * @flags: see V4L2_HEVC_DECODE_PARAM_FLAG_{}
@@ -2400,7 +2403,8 @@ struct v4l2_ctrl_hevc_decode_params {
 	__u8	poc_st_curr_before[V4L2_HEVC_DPB_ENTRIES_NUM_MAX];
 	__u8	poc_st_curr_after[V4L2_HEVC_DPB_ENTRIES_NUM_MAX];
 	__u8	poc_lt_curr[V4L2_HEVC_DPB_ENTRIES_NUM_MAX];
-	__u8	reserved[4];
+	__u8	num_delta_pocs_of_ref_rps_idx;
+	__u8	reserved[3];
 	struct	v4l2_hevc_dpb_entry dpb[V4L2_HEVC_DPB_ENTRIES_NUM_MAX];
 	__u64	flags;
 };
-- 
2.34.1