linux-kernel - Re: [PATCH v7 00/11] VP9 codec V4L2 control interface

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Message-ID: <63429780-9e39-f8ab-40c2-0f1b57553850@collabora.com>
Date:   Wed, 17 Nov 2021 11:49:05 +0100
From:   Andrzej Pietrasiewicz <andrzej.p@...labora.com>
To:     Hans Verkuil <hverkuil-cisco@...all.nl>,
        linux-media@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux-rockchip@...ts.infradead.org,
        linux-staging@...ts.linux.dev
Cc:     Benjamin Gaignard <benjamin.gaignard@...labora.com>,
        Boris Brezillon <boris.brezillon@...labora.com>,
        Ezequiel Garcia <ezequiel@...guardiasur.com.ar>,
        Fabio Estevam <festevam@...il.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Heiko Stuebner <heiko@...ech.de>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Nicolas Dufresne <nicolas.dufresne@...labora.com>,
        NXP Linux Team <linux-imx@....com>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Shawn Guo <shawnguo@...nel.org>, kernel@...labora.com
Subject: Re: [PATCH v7 00/11] VP9 codec V4L2 control interface

Hi,

W dniu 17.11.2021 o 10:59, Hans Verkuil pisze:
> On 16/11/2021 14:14, Andrzej Pietrasiewicz wrote:
>> Hi,
>>
>> W dniu 16.11.2021 o 09:21, Hans Verkuil pisze:
>>> On 16/11/2021 09:09, Andrzej Pietrasiewicz wrote:
>>>> Hi Hans,
>>>>
>>>> W dniu 15.11.2021 o 22:16, Hans Verkuil pisze:
>>>>> On 15/11/2021 18:14, Andrzej Pietrasiewicz wrote:
>>>>>> Hi Hans,
>>>>>>
>>>>>> W dniu 15.11.2021 o 16:07, Hans Verkuil pisze:
>>>>>>> Andrzej,
>>>>>>>
>>>>>>> Can you rebase this series on top of the master branch of
>>>>>>> https://git.linuxtv.org/media_stage.git/ ? Unfortunately this v7 no longer
>>>>>>> applies. Specifically "rkvdec: Add the VP9 backend" failed in a non-trivial
>>>>>>> manner.
>>>>>>
>>>>>> This is a branch for you:
>>>>>>
>>>>>> https://gitlab.collabora.com/linux/for-upstream/-/tree/vp9-uapi
>>>>>
>>>>> I'm getting a bunch of sparse/smatch warnings:
>>>>>
>>>>
>>>> Thanks for finding this, I will re-create the branch and let you know on irc.
>>>> Some of the below are "false positives, namely:
>>>>
>>>> drivers/media/platform/omap3isp/omap3isp.h
>>>> drivers/media/platform/qcom/venus/core.h
>>>
>>> Ah, sorry, I though I had filtered those out. Obviously you can ignore those.
>>>
>>> Please post a v8. That way the series is archived on lore. And it works better
>>> with patchwork.
>>
>> Sure, no problem. Also please see below.
>>
>>>
>>> Regards,
>>>
>>> 	Hans
>>>
>>>>
>>>> which are not touched by the series.
>>>>
>>>> Regards,
>>>>
>>>> Andrzej
>>>>
>>>>> sparse:
>>>>> rkvdec/rkvdec-vp9.c:190:43: warning: variable 'dec_params' set but not used [-Wunused-but-set-variable]
>>>>> rkvdec/rkvdec-vp9.c:245:43: warning: variable 'dec_params' set but not used [-Wunused-but-set-variable]
>>>>> SPARSE:hantro/hantro_postproc.c hantro/hantro_postproc.c:37:35: warning: symbol 'hantro_g1_postproc_regs' was not declared. Should it be static?
>>>>>
>>>>> smatch:
>>>>> rkvdec/rkvdec-vp9.c:190:43: warning: variable 'dec_params' set but not used [-Wunused-but-set-variable]
>>>>> rkvdec/rkvdec-vp9.c:245:43: warning: variable 'dec_params' set but not used [-Wunused-but-set-variable]
>>>>> rkvdec/rkvdec-vp9.c: rkvdec/rkvdec-vp9.c:236 init_intra_only_probs() error: buffer overflow 'ptr' 90 <= 91
>>
>> this looks a false positive.
>>
>> A portion of memory pointed to by ptr is indexed with i * 23 + m,
>> where i ranges from 0 to 3, inclusive, and m ranges from 0 to 22,
>> inclusive if i < 3, otherwise m ranges from 0 to 20, inclusive.
>> So the largest index value we compute equals 89 (3 * 23 + 20).
>> Because ptr points to something that is at least 90 bytes large,
>> 89 is a valid index and no greater index will be ever computed.
> 
> But we do need to get rid of this smatch warning, otherwise it will pollute the
> list of smatch warnings.
> 
> I was looking at the code and wonder if it wouldn't make more sense to
> move writing to rkprobs->intra_mode[i].uv_mode[] into a separate for loop:
> 
>          for (i = 0; i < ARRAY_SIZE(v4l2_vp9_kf_uv_mode_prob); i++)
>                  rkprobs->intra_mode[i / 23].uv_mode[i % 23] = v4l2_vp9_kf_uv_mode_prob[i];
> 
> Wouldn't that do the same as the current code? It looks simpler as well.
> 

I think it would, but I would slightly change the loop:

	for (i = 0; i < ARRAY_SIZE(v4l2_vp9_kf_uv_mode_prob); i++) {
		const u8 *ptr = (const u8 *)v4l2_vp9_kf_uv_mode_prob;

		rkprobs->intra_mode[i / 23].uv_mode[i % 23] = ptr[i];
	}

because v4l2_vp9_kf_uv_mode_prob is actually a u8[10][9].

I will make such a change locally and test whether it causes regressions.

Once I confirm it works (and I expect I will) would you like me to post a v9,
only reply to the changed patch with its updated version or do you want to make 
this change yourself?

Andrzej