linux-kernel - Re: [PATCH v2] staging: media: meson: vdec: declare u32 as const and static const

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Message-ID: <88d04746-717d-5a7a-7ea7-67cf6c95aba9@xs4all.nl>
Date:   Mon, 12 Apr 2021 11:17:22 +0200
From:   Hans Verkuil <hverkuil@...all.nl>
To:     Mitali Borkar <mitaliborkar810@...il.com>, narmstrong@...libre.com,
        mchehab@...nel.org, gregkh@...uxfoundation.org,
        khilman@...libre.com, jbrunet@...libre.com,
        martin.blumenstingl@...glemail.com
Cc:     linux-media@...r.kernel.org, linux-staging@...ts.linux.dev,
        linux-kernel@...r.kernel.org, outreachy-kernel@...glegroups.com,
        mitali_s@...iitr.ac.in, linux-amlogic@...ts.infradead.org
Subject: Re: [PATCH v2] staging: media: meson: vdec: declare u32 as const and
 static const

On 10/04/2021 21:59, Mitali Borkar wrote:
> Declared 32 bit unsigned int as static constant inside a function and
> replaced u32[] {x,y} as canvas1, canvas2 in codec_mpeg12.c
> This indicates the value of canvas indexes will remain constant throughout execution.
> Replaced u32 reg_base and u32 reg_name with const u32 reg_base and const
> u32 reg_name as it will contain data/registry bases to write static
> const indexes declared above and will keep track of of contiguos
> registers after each reg_base.
> This makes code look better, neater. It improves readability.
> 
> Signed-off-by: Mitali Borkar <mitaliborkar810@...il.com>
> ---
>  drivers/staging/media/meson/vdec/codec_mpeg12.c | 5 +++--

Also change drivers/staging/media/meson/vdec/codec_h264.c.

It's a nice improvement, so let's do this for both callers of amvdec_set_canvases().

Regards,

	Hans

>  drivers/staging/media/meson/vdec/vdec_helpers.c | 2 +-
>  drivers/staging/media/meson/vdec/vdec_helpers.h | 2 +-
>  3 files changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/staging/media/meson/vdec/codec_mpeg12.c b/drivers/staging/media/meson/vdec/codec_mpeg12.c
> index 21e93a13356c..861d8584f22f 100644
> --- a/drivers/staging/media/meson/vdec/codec_mpeg12.c
> +++ b/drivers/staging/media/meson/vdec/codec_mpeg12.c
> @@ -65,6 +65,8 @@ static int codec_mpeg12_start(struct amvdec_session *sess)
>  	struct amvdec_core *core = sess->core;
>  	struct codec_mpeg12 *mpeg12;
>  	int ret;
> +	static const u32 canvas1[] = { AV_SCRATCH_0, 0 };
> +	static const u32 canvas2[] = { 8, 0 }
>  
>  	mpeg12 = kzalloc(sizeof(*mpeg12), GFP_KERNEL);
>  	if (!mpeg12)
> @@ -80,8 +82,7 @@ static int codec_mpeg12_start(struct amvdec_session *sess)
>  		goto free_mpeg12;
>  	}
>  
> -	ret = amvdec_set_canvases(sess, (u32[]){ AV_SCRATCH_0, 0 },
> -				  (u32[]){ 8, 0 });
> +	ret = amvdec_set_canvases(sess, canvas1, canvas2);
>  	if (ret)
>  		goto free_workspace;
>  
> diff --git a/drivers/staging/media/meson/vdec/vdec_helpers.c b/drivers/staging/media/meson/vdec/vdec_helpers.c
> index 7f07a9175815..df5c27266c44 100644
> --- a/drivers/staging/media/meson/vdec/vdec_helpers.c
> +++ b/drivers/staging/media/meson/vdec/vdec_helpers.c
> @@ -177,7 +177,7 @@ static int set_canvas_nv12m(struct amvdec_session *sess,
>  }
>  
>  int amvdec_set_canvases(struct amvdec_session *sess,
> -			u32 reg_base[], u32 reg_num[])
> +			const u32 reg_base[], const u32 reg_num[])
>  {
>  	struct v4l2_m2m_buffer *buf;
>  	u32 pixfmt = sess->pixfmt_cap;
> diff --git a/drivers/staging/media/meson/vdec/vdec_helpers.h b/drivers/staging/media/meson/vdec/vdec_helpers.h
> index cfaed52ab526..ace8897c34fe 100644
> --- a/drivers/staging/media/meson/vdec/vdec_helpers.h
> +++ b/drivers/staging/media/meson/vdec/vdec_helpers.h
> @@ -17,7 +17,7 @@
>   * @reg_num: number of contiguous registers after each reg_base (including it)
>   */
>  int amvdec_set_canvases(struct amvdec_session *sess,
> -			u32 reg_base[], u32 reg_num[]);
> +			const u32 reg_base[], const u32 reg_num[]);
>  
>  /* Helpers to read/write to the various IPs (DOS, PARSER) */
>  u32 amvdec_read_dos(struct amvdec_core *core, u32 reg);
>