linux-kernel - Re: [PATCH v8 12/13] [media] v4l: Add V4L2_CAP

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Date:   Wed, 14 Mar 2018 09:07:52 -0700
From:   Hans Verkuil <hverkuil@...all.nl>
To:     Gustavo Padovan <gustavo@...ovan.org>, linux-media@...r.kernel.org
Cc:     kernel@...labora.com,
        Mauro Carvalho Chehab <mchehab@....samsung.com>,
        Shuah Khan <shuahkh@....samsung.com>,
        Pawel Osciak <pawel@...iak.com>,
        Alexandre Courbot <acourbot@...omium.org>,
        Sakari Ailus <sakari.ailus@....fi>,
        Brian Starkey <brian.starkey@....com>,
        linux-kernel@...r.kernel.org,
        Gustavo Padovan <gustavo.padovan@...labora.com>
Subject: Re: [PATCH v8 12/13] [media] v4l: Add V4L2_CAP_FENCES to drivers

On 03/09/2018 09:49 AM, Gustavo Padovan wrote:
> From: Gustavo Padovan <gustavo.padovan@...labora.com>
> 
> Drivers that use videobuf2 are capable of using fences and
> should report that to userspace.
> 
> The coding style is following what each drivers was already
> doing.

I think this can be simplified for most drivers: you can set this
flag in the v4l_querycap function if vdev->queue is not NULL or if
m2m_ctx is set in struct v4l2_fh.

I believe all non-m2m drivers that use vb2 set vdev->queue. But not
all m2m drivers will set m2m_ctx, so that will need to be checked.

In other words, this way you only need to modify m2m drivers that
do not set m2m_ctx.

Regards,

	Hans