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

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Date:   Tue, 7 Aug 2018 15:55:08 +0900
From:   Tomasz Figa <tfiga@...omium.org>
To:     Philipp Zabel <p.zabel@...gutronix.de>
Cc:     Hans Verkuil <hverkuil@...all.nl>,
        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, Jul 26, 2018 at 7:36 PM Philipp Zabel <p.zabel@...gutronix.de> wrote:
>
> 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.

Thanks for clarifying. I forgot about that internal copy indeed.

Best regards,
Tomasz