linux-kernel - Re: [PATCH 1/3] media: mediatek: vcodec: fix h264 multi statless decoder smatch warning

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Date: Wed, 29 May 2024 15:14:21 +0200
From: Andrzej Pietrasiewicz <andrzej.p@...labora.com>
To: Yunfei Dong (董云飞) <Yunfei.Dong@...iatek.com>,
 "nhebert@...omium.org" <nhebert@...omium.org>,
 "benjamin.gaignard@...labora.com" <benjamin.gaignard@...labora.com>,
 "nfraprado@...labora.com" <nfraprado@...labora.com>,
 "angelogioacchino.delregno@...labora.com"
 <angelogioacchino.delregno@...labora.com>,
 "nicolas.dufresne@...labora.com" <nicolas.dufresne@...labora.com>,
 "hverkuil-cisco@...all.nl" <hverkuil-cisco@...all.nl>
Cc: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
 "linux-mediatek@...ts.infradead.org" <linux-mediatek@...ts.infradead.org>,
 "frkoenig@...omium.org" <frkoenig@...omium.org>,
 "stevecho@...omium.org" <stevecho@...omium.org>,
 "linux-media@...r.kernel.org" <linux-media@...r.kernel.org>,
 "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
 "daniel@...ll.ch" <daniel@...ll.ch>,
 Project_Global_Chrome_Upstream_Group
 <Project_Global_Chrome_Upstream_Group@...iatek.com>,
 "hsinyi@...omium.org" <hsinyi@...omium.org>,
 "linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 1/3] media: mediatek: vcodec: fix h264 multi statless
 decoder smatch warning

Hi,

W dniu 3.04.2024 o 05:45, Yunfei Dong (董云飞) pisze:
> Hi AngeloGioacchino,
> 
> Thanks for your reviewing.
> On Tue, 2024-04-02 at 11:50 +0200, AngeloGioacchino Del Regno wrote:
>> Il 29/02/24 10:56, Yunfei Dong ha scritto:
>>> Fix smatch static checker warning for vdec_h264_req_multi_if.c.
>>> Leading to kernel crash when fb is NULL.
>>>
>>> Fixes: 397edc703a10 ("media: mediatek: vcodec: add h264 decoder")
>>> Signed-off-by: Yunfei Dong <yunfei.dong@...iatek.com>
>>> ---
>>>    .../vcodec/decoder/vdec/vdec_h264_req_multi_if.c         | 9
>>> +++++++--
>>>    1 file changed, 7 insertions(+), 2 deletions(-)
>>>
>>> diff --git
>>> a/drivers/media/platform/mediatek/vcodec/decoder/vdec/vdec_h264_req
>>> _multi_if.c
>>> b/drivers/media/platform/mediatek/vcodec/decoder/vdec/vdec_h264_req
>>> _multi_if.c
>>> index 0e741e0dc8ba..ab8e708e0df1 100644
>>> ---
>>> a/drivers/media/platform/mediatek/vcodec/decoder/vdec/vdec_h264_req
>>> _multi_if.c
>>> +++
>>> b/drivers/media/platform/mediatek/vcodec/decoder/vdec/vdec_h264_req
>>> _multi_if.c
>>> @@ -724,11 +724,16 @@ static int vdec_h264_slice_single_decode(void
>>> *h_vdec, struct mtk_vcodec_mem *bs
>>>    		return vpu_dec_reset(vpu);
>>>    
>>>    	fb = inst->ctx->dev->vdec_pdata->get_cap_buffer(inst->ctx);
>>> +	if (!fb) {
>>> +		mtk_vdec_err(inst->ctx, "fb buffer is NULL");
>>> +		return -EBUSY;
>>> +	}
>>> +
>>>    	src_buf_info = container_of(bs, struct mtk_video_dec_buf,
>>> bs_buffer);
>>>    	dst_buf_info = container_of(fb, struct mtk_video_dec_buf,
>>> frame_buffer);
>>>    
>>> -	y_fb_dma = fb ? (u64)fb->base_y.dma_addr : 0;
>>> -	c_fb_dma = fb ? (u64)fb->base_c.dma_addr : 0;
>>
>> You're changing the behavior here, can you please explain why this
>> change is valid
>> into the commit description?
>>
> The driver already add the condition to check whether fb is NULL at the
> front, no need these two lines again.
> 

Maybe Angelo refers to the function never returning -EBUSY before?
While at it, if fb is a kind of a buffer, why not -ENOMEM
when get_cap_buffer() fails?

Regards,

Andrzej

>> Thanks,
>> Angelo
>>
> Best Regards,
> Yunfei Dong
>>> +	y_fb_dma = (u64)fb->base_y.dma_addr;
>>> +	c_fb_dma = (u64)fb->base_c.dma_addr;
>>>    	mtk_vdec_debug(inst->ctx, "[h264-dec] [%d] y_dma=%llx
>>> c_dma=%llx",
>>>    		       inst->ctx->decoded_frame_cnt, y_fb_dma,
>>> c_fb_dma);
>>>    
>>
>>
>>