linux-kernel - Re: [PATCH 2/2] media: venus: venc: fix bytesused v4l2

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Message-ID: <47d29965-667d-fe41-1121-bb1e573e8bfe@linaro.org>
Date:   Tue, 10 Oct 2017 01:17:44 +0300
From:   Stanimir Varbanov <stanimir.varbanov@...aro.org>
To:     Hans Verkuil <hverkuil@...all.nl>
Cc:     Nicolas Dufresne <nicolas@...fresne.ca>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH 2/2] media: venus: venc: fix bytesused v4l2_plane field

Hans,

On  9.10.2017 15:31, Hans Verkuil wrote:
> On 09/10/17 14:24, Stanimir Varbanov wrote:
>> This fixes wrongly filled bytesused field of v4l2_plane structure
>> by include data_offset in the plane, Also fill data_offset and
>> bytesused for capture type of buffers only.
>>
>> Signed-off-by: Stanimir Varbanov <stanimir.varbanov@...aro.org>
>> ---
>>   drivers/media/platform/qcom/venus/venc.c | 9 +++++----
>>   1 file changed, 5 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/media/platform/qcom/venus/venc.c b/drivers/media/platform/qcom/venus/venc.c
>> index 6f123a387cf9..9445ad492966 100644
>> --- a/drivers/media/platform/qcom/venus/venc.c
>> +++ b/drivers/media/platform/qcom/venus/venc.c
>> @@ -963,15 +963,16 @@ static void venc_buf_done(struct venus_inst *inst, unsigned int buf_type,
>>   	if (!vbuf)
>>   		return;
>>   
>> -	vb = &vbuf->vb2_buf;
>> -	vb->planes[0].bytesused = bytesused;
>> -	vb->planes[0].data_offset = data_offset;
>> -
>>   	vbuf->flags = flags;
>>   
>>   	if (type == V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE) {
>> +		vb = &vbuf->vb2_buf;
>> +		vb2_set_plane_payload(vb, 0, bytesused + data_offset);
>> +		vb->planes[0].data_offset = data_offset;
>>   		vb->timestamp = timestamp_us * NSEC_PER_USEC;
>>   		vbuf->sequence = inst->sequence_cap++;
>> +
>> +		WARN_ON(vb2_get_plane_payload(vb, 0) > vb2_plane_size(vb, 0));
> 
> It's good to have this, but this really should never happen. Because if it is,
> then you'll have a memory overwrite. I hope the DMA engine will prevent this? >
> Just wondering how this works.
> 
> The patch looks good otherwise, but that WARN_ON is a bit scary.

Infact it is not so scary as it looks like, the IOMMU will catch this 
and generate a fault. So most probably we will never come to the WARN, 
thus the warning is pointless so will delete it.

regards,
Stan