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SubjectRe: [PATCH v2 01/18] media: allegro: nal-hevc: Refactor nal_hevc_sub_layer_hrd_parameters
On Tue, 07 May 2024 16:27:06 +0000, Ricardo Ribalda wrote:
> Replace all the single elements arrays with the element itself.
>
> Pahole shows the same padding and alignment for x86 and arm in both
> situations.
>
> This fixes this cocci warning:
> drivers/media/platform/allegro-dvt/nal-hevc.h:102:14-22: WARNING use flexible-array member instead (https://www.kernel.org/doc/html/latest/process/deprecated.html#zero-length-and-one-element-arrays)

Thanks for the patch.

>
> Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
> ---
> drivers/media/platform/allegro-dvt/allegro-core.c | 6 +++---
> drivers/media/platform/allegro-dvt/nal-hevc.c | 11 +++--------
> drivers/media/platform/allegro-dvt/nal-hevc.h | 6 +++---
> 3 files changed, 9 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/media/platform/allegro-dvt/allegro-core.c b/drivers/media/platform/allegro-dvt/allegro-core.c
> index da61f9beb6b4..369bd88cc0ae 100644
> --- a/drivers/media/platform/allegro-dvt/allegro-core.c
> +++ b/drivers/media/platform/allegro-dvt/allegro-core.c
> @@ -1852,14 +1852,14 @@ static ssize_t allegro_hevc_write_sps(struct allegro_channel *channel,
> hrd->dpb_output_delay_length_minus1 = 30;
>
> hrd->bit_rate_scale = ffs(channel->bitrate_peak) - 6;
> - hrd->vcl_hrd[0].bit_rate_value_minus1[0] =
> + hrd->vcl_hrd[0].bit_rate_value_minus1 =
> (channel->bitrate_peak >> (6 + hrd->bit_rate_scale)) - 1;
>
> cpb_size = v4l2_ctrl_g_ctrl(channel->mpeg_video_cpb_size) * 1000;
> hrd->cpb_size_scale = ffs(cpb_size) - 4;
> - hrd->vcl_hrd[0].cpb_size_value_minus1[0] = (cpb_size >> (4 + hrd->cpb_size_scale)) - 1;
> + hrd->vcl_hrd[0].cpb_size_value_minus1 = (cpb_size >> (4 + hrd->cpb_size_scale)) - 1;
>
> - hrd->vcl_hrd[0].cbr_flag[0] = !v4l2_ctrl_g_ctrl(channel->mpeg_video_frame_rc_enable);
> + hrd->vcl_hrd[0].cbr_flag = !v4l2_ctrl_g_ctrl(channel->mpeg_video_frame_rc_enable);
>
> size = nal_hevc_write_sps(&dev->plat_dev->dev, dest, n, sps);
>
> diff --git a/drivers/media/platform/allegro-dvt/nal-hevc.c b/drivers/media/platform/allegro-dvt/nal-hevc.c
> index 9cdf2756e0a3..575089522df5 100644
> --- a/drivers/media/platform/allegro-dvt/nal-hevc.c
> +++ b/drivers/media/platform/allegro-dvt/nal-hevc.c
> @@ -210,14 +210,9 @@ static void nal_hevc_rbsp_vps(struct rbsp *rbsp, struct nal_hevc_vps *vps)
> static void nal_hevc_rbsp_sub_layer_hrd_parameters(struct rbsp *rbsp,
> struct nal_hevc_sub_layer_hrd_parameters *hrd)
> {
> - unsigned int i;
> - unsigned int cpb_cnt = 1;
> -
> - for (i = 0; i < cpb_cnt; i++) {
> - rbsp_uev(rbsp, &hrd->bit_rate_value_minus1[i]);
> - rbsp_uev(rbsp, &hrd->cpb_size_value_minus1[i]);
> - rbsp_bit(rbsp, &hrd->cbr_flag[i]);
> - }
> + rbsp_uev(rbsp, &hrd->bit_rate_value_minus1);
> + rbsp_uev(rbsp, &hrd->cpb_size_value_minus1);
> + rbsp_bit(rbsp, &hrd->cbr_flag);
> }
>
> static void nal_hevc_rbsp_hrd_parameters(struct rbsp *rbsp,
> diff --git a/drivers/media/platform/allegro-dvt/nal-hevc.h b/drivers/media/platform/allegro-dvt/nal-hevc.h
> index eb46f12aae80..afa7a9d7d654 100644
> --- a/drivers/media/platform/allegro-dvt/nal-hevc.h
> +++ b/drivers/media/platform/allegro-dvt/nal-hevc.h
> @@ -97,9 +97,9 @@ struct nal_hevc_vps {
> };
>
> struct nal_hevc_sub_layer_hrd_parameters {
> - unsigned int bit_rate_value_minus1[1];
> - unsigned int cpb_size_value_minus1[1];
> - unsigned int cbr_flag[1];
> + unsigned int bit_rate_value_minus1;
> + unsigned int cpb_size_value_minus1;
> + unsigned int cbr_flag;

The struct is modeled after the specification in ITU-T H.265, which
defines the fields as arrays. It's a limitation of the current
implementation that only a single element is supported.

Maybe replacing the hard coded values with a constant would be more
appropriate to document this limitation.

Michael

> };
>
> struct nal_hevc_hrd_parameters {
>
> --
> 2.45.0.rc1.225.g2a3ae87e7f-goog
>
>

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