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Subject: Re: [PATCH 1/2] media: docs-rst: Document memory-to-memory video
 decoder interface
From:   Philipp Zabel <p.zabel@pengutronix.de>
To:     Tomasz Figa <tfiga@chromium.org>, Hans Verkuil <hverkuil@xs4all.nl>
Cc:     Linux Media Mailing List <linux-media@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Stanimir Varbanov <stanimir.varbanov@linaro.org>,
        Mauro Carvalho Chehab <mchehab@kernel.org>,
        Pawel Osciak <posciak@chromium.org>,
        Alexandre Courbot <acourbot@chromium.org>, kamil@wypas.org,
        a.hajda@samsung.com, Kyungmin Park <kyungmin.park@samsung.com>,
        jtp.park@samsung.com,
        Tiffany Lin =?UTF-8?Q?=28=E6=9E=97=E6=85=A7=E7=8F=8A=29?= 
        <tiffany.lin@mediatek.com>,
        Andrew-CT Chen =?UTF-8?Q?=28=E9=99=B3=E6=99=BA=E8=BF=AA=29?= 
        <andrew-ct.chen@mediatek.com>, todor.tomov@linaro.org,
        nicolas@ndufresne.ca,
        Paul Kocialkowski <paul.kocialkowski@bootlin.com>,
        Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
        dave.stevenson@raspberrypi.org,
        Ezequiel Garcia <ezequiel@collabora.com>
Date:   Thu, 26 Jul 2018 12:36:41 +0200
In-Reply-To: <CAAFQd5BgGEBmd8gNGc-qqtUtLo=Mh8U+TVTWRsKYMv1LmeBQMA@mail.gmail.com>
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         <37a8faea-a226-2d52-36d4-f9df194623cc@xs4all.nl>
         <CAAFQd5BgGEBmd8gNGc-qqtUtLo=Mh8U+TVTWRsKYMv1LmeBQMA@mail.gmail.com>
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On Thu, 2018-07-26 at 19:20 +0900, Tomasz Figa wrote:
[...]
> > You might want to mention that if there are insufficient buffers, then
> > VIDIOC_CREATE_BUFS can be used to add more buffers.
> > 
> 
> This might be a bit tricky, since at least s5p-mfc and coda can only
> work on a fixed buffer set and one would need to fully reinitialize
> the decoding to add one more buffer, which would effectively be the
> full resolution change sequence, as below, just with REQBUFS(0),
> REQBUFS(N) replaced with CREATE_BUFS.

The coda driver supports CREATE_BUFS on the decoder CAPTURE queue.

The firmware indeed needs a fixed frame buffer set, but these buffers
are internal only and in a coda specific tiling format. The content of
finished internal buffers is copied / detiled into the external CAPTURE
buffers, so those can be added at will.

regards
Philipp