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

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Message-ID: <YHRA9i+BjveJOUvn@kali>
Date:   Mon, 12 Apr 2021 18:15:42 +0530
From:   Mitali Borkar <mitaliborkar810@...il.com>
To:     Hans Verkuil <hverkuil@...all.nl>, 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 Mon, Apr 12, 2021 at 11:17:22AM +0200, Hans Verkuil wrote:
> 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().
>
I have done chnages in codec_h264.c Now, should I send that as new
patch?

> 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);
> > 
>