linux-kernel - Re: [PATCH 1/2] media: docs-rst: Document memory-to-memory video decoder interface

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Date:   Thu, 26 Jul 2018 12:36:41 +0200
From:   Philipp Zabel <p.zabel@...gutronix.de>
To:     Tomasz Figa <tfiga@...omium.org>, Hans Verkuil <hverkuil@...all.nl>
Cc:     Linux Media Mailing List <linux-media@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Stanimir Varbanov <stanimir.varbanov@...aro.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Pawel Osciak <posciak@...omium.org>,
        Alexandre Courbot <acourbot@...omium.org>, kamil@...as.org,
        a.hajda@...sung.com, Kyungmin Park <kyungmin.park@...sung.com>,
        jtp.park@...sung.com,
        Tiffany Lin (林慧珊) 
        <tiffany.lin@...iatek.com>,
        Andrew-CT Chen (陳智迪) 
        <andrew-ct.chen@...iatek.com>, todor.tomov@...aro.org,
        nicolas@...fresne.ca,
        Paul Kocialkowski <paul.kocialkowski@...tlin.com>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        dave.stevenson@...pberrypi.org,
        Ezequiel Garcia <ezequiel@...labora.com>
Subject: Re: [PATCH 1/2] media: docs-rst: Document memory-to-memory video
 decoder interface

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