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

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Message-ID: <6107204d-f1a3-0888-ef3b-88520d786fa1@baylibre.com>
Date:   Mon, 12 Apr 2021 14:48:25 +0200
From:   Neil Armstrong <narmstrong@...libre.com>
To:     Mitali Borkar <mitaliborkar810@...il.com>,
        Hans Verkuil <hverkuil@...all.nl>, 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 12/04/2021 14:45, Mitali Borkar wrote:
> 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?

Yes please,

Neil

> 
>> 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);
>>>
>>