linux-kernel - Re: [RFC 2/7] fixup! media: uapi: h264: update reference lists

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Date:   Thu, 25 Jun 2020 10:53:02 -0400
From:   Nicolas Dufresne <nicolas.dufresne@...labora.com>
To:     Ezequiel Garcia <ezequiel@...labora.com>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Tomasz Figa <tfiga@...omium.org>, kernel@...labora.com,
        Jonas Karlman <jonas@...boo.se>,
        Hans Verkuil <hverkuil@...all.nl>,
        Alexandre Courbot <acourbot@...omium.org>,
        Jeffrey Kardatzke <jkardatzke@...omium.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Maxime Ripard <mripard@...nel.org>,
        Paul Kocialkowski <paul.kocialkowski@...tlin.com>
Subject: Re: [RFC 2/7] fixup! media: uapi: h264: update reference lists

Le mardi 23 juin 2020 à 15:28 -0300, Ezequiel Garcia a écrit :
> Align v4l2_h264_reference to 32-bits, giving some room
> for future extensions.
> 
> Signed-off-by: Ezequiel Garcia <ezequiel@...labora.com>
> ---
>  .../userspace-api/media/v4l/ext-ctrls-codec.rst  |  3 +++
>  drivers/media/v4l2-core/v4l2-ctrls.c             | 16 ++++++++++++++++
>  include/media/h264-ctrls.h                       |  7 +++++--
>  3 files changed, 24 insertions(+), 2 deletions(-)
> 
> diff --git a/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst b/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
> index 6c36d298db20..7af12447a5b0 100644
> --- a/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
> +++ b/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
> @@ -1943,6 +1943,9 @@ enum v4l2_mpeg_video_h264_hierarchical_coding_type -
>      * - __u8
>        - ``index``
>        -
> +    * - __u32
> +      - ``reserved``
> +      - Applications and drivers must set this to zero.

Is that really appropriate ? There was some effort to keep the controls
small. Also, as these are fixed size, they could be extended with
supplementary C arrays of the same size, set in separate control.

Also, H264 HW is unlikely to evolve, and that covers what DXVA2 and
VAAPI covers already. So it is quite unlikely to ever have to be
extended.

>  
>  .. _h264_reference_flags:
>  
> diff --git a/drivers/media/v4l2-core/v4l2-ctrls.c b/drivers/media/v4l2-core/v4l2-ctrls.c
> index 3f3fbcd60cc6..6abd023f10c7 100644
> --- a/drivers/media/v4l2-core/v4l2-ctrls.c
> +++ b/drivers/media/v4l2-core/v4l2-ctrls.c
> @@ -1721,6 +1721,8 @@ static void std_log(const struct v4l2_ctrl *ctrl)
>  
>  #define zero_padding(s) \
>  	memset(&(s).padding, 0, sizeof((s).padding))
> +#define zero_reserved(s) \
> +	memset(&(s).reserved, 0, sizeof((s).reserved))
>  
>  /*
>   * Compound controls validation requires setting unused fields/flags to zero
> @@ -1731,6 +1733,7 @@ static int std_validate_compound(const struct v4l2_ctrl *ctrl, u32 idx,
>  {
>  	struct v4l2_ctrl_mpeg2_slice_params *p_mpeg2_slice_params;
>  	struct v4l2_ctrl_vp8_frame_header *p_vp8_frame_header;
> +	struct v4l2_ctrl_h264_slice_params *p_h264_slice_params;
>  	struct v4l2_ctrl_hevc_sps *p_hevc_sps;
>  	struct v4l2_ctrl_hevc_pps *p_hevc_pps;
>  	struct v4l2_ctrl_hevc_slice_params *p_hevc_slice_params;
> @@ -1790,7 +1793,20 @@ static int std_validate_compound(const struct v4l2_ctrl *ctrl, u32 idx,
>  	case V4L2_CTRL_TYPE_H264_SPS:
>  	case V4L2_CTRL_TYPE_H264_PPS:
>  	case V4L2_CTRL_TYPE_H264_SCALING_MATRIX:
> +		break;
>  	case V4L2_CTRL_TYPE_H264_SLICE_PARAMS:
> +		p_h264_slice_params = p;
> +
> +		for (i = 0; i < V4L2_H264_REF_PIC_LIST_LEN; i++) {
> +			struct v4l2_h264_reference *ref0 =
> +				&p_h264_slice_params->ref_pic_list0[i];
> +			struct v4l2_h264_reference *ref1 =
> +				&p_h264_slice_params->ref_pic_list1[i];
> +
> +			zero_reserved(*ref0);
> +			zero_reserved(*ref1);
> +		}
> +		break;
>  	case V4L2_CTRL_TYPE_H264_DECODE_PARAMS:
>  		break;
>  
> diff --git a/include/media/h264-ctrls.h b/include/media/h264-ctrls.h
> index 9b1cbc9bc38e..c6cbf178c1c9 100644
> --- a/include/media/h264-ctrls.h
> +++ b/include/media/h264-ctrls.h
> @@ -19,6 +19,8 @@
>   */
>  #define V4L2_H264_NUM_DPB_ENTRIES 16
>  
> +#define V4L2_H264_REF_PIC_LIST_LEN 32
> +
>  /* Our pixel format isn't stable at the moment */
>  #define V4L2_PIX_FMT_H264_SLICE v4l2_fourcc('S', '2', '6', '4') /* H264 parsed slices */
>  
> @@ -146,6 +148,7 @@ struct v4l2_h264_pred_weight_table {
>  struct v4l2_h264_reference {
>  	__u8 flags;
>  	__u8 index;
> +	__u16 reserved;
>  };
>  
>  struct v4l2_ctrl_h264_slice_params {
> @@ -190,8 +193,8 @@ struct v4l2_ctrl_h264_slice_params {
>  	 * Entries on each list are indices into
>  	 * v4l2_ctrl_h264_decode_params.dpb[].
>  	 */
> -	struct v4l2_h264_reference ref_pic_list0[32];
> -	struct v4l2_h264_reference ref_pic_list1[32];
> +	struct v4l2_h264_reference ref_pic_list0[V4L2_H264_REF_PIC_LIST_LEN];
> +	struct v4l2_h264_reference ref_pic_list1[V4L2_H264_REF_PIC_LIST_LEN];
>  
>  	__u32 flags;
>  };

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