linux-kernel - Re: [PATCH v2] media/doc: Allow sizeimage to be set by v4l clients

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Message-ID: <ca0e2c94-cca9-567f-5376-f302f79f4ba7@linaro.org>
Date:   Thu, 16 May 2019 11:09:06 +0300
From:   Stanimir Varbanov <stanimir.varbanov@...aro.org>
To:     Hans Verkuil <hverkuil@...all.nl>,
        Stanimir Varbanov <stanimir.varbanov@...aro.org>,
        linux-media@...r.kernel.org
Cc:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Tomasz Figa <tfiga@...omium.org>
Subject: Re: [PATCH v2] media/doc: Allow sizeimage to be set by v4l clients

Hi Hans,

On 5/14/19 11:54 AM, Hans Verkuil wrote:
> Hi Stanimir,
> 
> On 4/12/19 5:59 PM, Stanimir Varbanov wrote:
>> This changes v4l2_pix_format and v4l2_plane_pix_format sizeimage
>> field description to allow v4l clients to set bigger image size
>> in case of variable length compressed data.
> 
> I've been reconsidering this change. The sizeimage value in the format
> is the minimum size a buffer should have in order to store the data of
> an image of the width and height as described in the format.
> 
> But there is nothing that prevents userspace from calling VIDIOC_CREATEBUFS
> instead of VIDIOC_REQBUFS to allocate larger buffers.

Sometimes CREATEBUFS cannot be implemented for a particular fw/hw.

CC: Tomasz for his opinion.

> 
> So do we really need this change?
> 
> The more I think about this, the more uncomfortable I become with this change.
> 
> Regards,
> 
> 	Hans
> 

<cut>

-- 
regards,
Stan