linux-kernel - Re: [PATCH v3] media: venus: amend buffer size for bitstream plane

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Date:   Mon, 26 Nov 2018 16:57:37 +0200
From:   Stanimir Varbanov <stanimir.varbanov@...aro.org>
To:     Hans Verkuil <hverkuil@...all.nl>,
        Malathi Gottam <mgottam@...eaurora.org>, mchehab@...nel.org
Cc:     linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, acourbot@...omium.org,
        vgarodia@...eaurora.org
Subject: Re: [PATCH v3] media: venus: amend buffer size for bitstream plane

Hi Hans,

On 11/26/18 3:37 PM, Hans Verkuil wrote:
> On 11/26/2018 11:12 AM, Malathi Gottam wrote:
>> Accept the buffer size requested by client and compare it
>> against driver calculated size and set the maximum to
>> bitstream plane.
>>
>> Signed-off-by: Malathi Gottam <mgottam@...eaurora.org>
> 
> Sorry, this isn't allowed. It is the driver that sets the sizeimage value,
> never the other way around.

I think for decoders (OUTPUT queue) and encoders (CAPTURE queue) we
allowed userspace to set sizeimage for buffers. See [1] Initialization
paragraph point 2:

    ``sizeimage``
       desired size of ``CAPTURE`` buffers; the encoder may adjust it to
       match hardware requirements

Similar patch we be needed for decoder as well.

> 
> If you need to allocate larger buffers, then use VIDIOC_CREATE_BUFS instead
> of VIDIOC_REQBUFS.
> 
> What problem are you trying to solve with this patch?
> 
> Regards,
> 
> 	Hans
> 

-- 
regards,
Stan

[1] https://www.spinics.net/lists/linux-media/msg142049.html