Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Message-ID: <09e608da8abeb4cd9c84bf9f559af2438540eb2b.camel@ndufresne.ca>
Subject: Re: [PATCH v7 2/4] media: videodev2: add
 V4L2_FMT_FLAG_FIXED_RESOLUTION
From:   Nicolas Dufresne <nicolas@ndufresne.ca>
To:     Philipp Zabel <p.zabel@pengutronix.de>,
        Hans Verkuil <hverkuil@xs4all.nl>,
        Maxime Jourdan <mjourdan@baylibre.com>,
        Mauro Carvalho Chehab <mchehab@kernel.org>,
        Hans Verkuil <hans.verkuil@cisco.com>
Cc:     Kevin Hilman <khilman@baylibre.com>,
        Jerome Brunet <jbrunet@baylibre.com>,
        Neil Armstrong <narmstrong@baylibre.com>,
        Martin Blumenstingl <martin.blumenstingl@googlemail.com>,
        linux-media@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org,
        linux-amlogic@lists.infradead.org
Date:   Tue, 11 Jun 2019 21:00:12 -0400
In-Reply-To: <1d2adae2b6d0f370f17b9bac94ae4e9207dccbad.camel@ndufresne.ca>
References: <20190531093126.26956-1-mjourdan@baylibre.com>
         <20190531093126.26956-3-mjourdan@baylibre.com>
         <9731b2db-efd4-87d0-c48d-87adec433747@xs4all.nl>
         <1560243127.13886.3.camel@pengutronix.de>
         <1d2adae2b6d0f370f17b9bac94ae4e9207dccbad.camel@ndufresne.ca>
Content-Type: text/plain; charset="UTF-8"
User-Agent: Evolution 3.32.2 (3.32.2-1.fc30) 
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Le mardi 11 juin 2019 à 20:58 -0400, Nicolas Dufresne a écrit :
> Le mardi 11 juin 2019 à 10:52 +0200, Philipp Zabel a écrit :
> > On Wed, 2019-06-05 at 15:39 +0200, Hans Verkuil wrote:
> > > Hi Maxime,
> > > 
> > > I am wondering if this flag shouldn't be inverted: you set
> > > V4L2_FMT_FLAG_DYN_RESOLUTION if dynamic resolution is supported,
> > > otherwise it isn't.
> > > 
> > > Can all the existing mainlined codec drivers handle midstream
> > > resolution changes?
> > > 
> > > s5p-mfc, venus and mediatek can, but I see no SOURCE_CHANGE event in
> > > the coda drivers, so I suspect that that can't handle this.
> > > 
> > > Philipp, what is the status of the coda driver for dynamic resolution
> > > changes?
> > 
> > FTR, to my knowledge there is no dynamic resolution change support in
> > the firmware, as there is no signal (interrupt nor picture run return
> > value) to indicate that different headers were parsed.
> > 
> > I am planning to add the initial source change event required by the
> > current decoder API documentation, but I am afraid there will be no
> > support for source changes due to mid-stream resolution changes due to
> > firmware limitations.
> 
> I'm far from familiar with this IP, but at least on CODA988, I can read
> from the manual that the workflow is to first guess the allocation, and
> if you guess it wrong, an error is returned. What seems to match the
> SOURCE_CHANGE event in that version would be in the picture status
> register, the bit 20, which is documented as triggered if the stream
> requires bigger buffers sizes, or more buffers. After fixing that, you
> should, if I read correctly, retry.
> 
> It does not notify if the buffers are too large, but you can detect,
> since there is register with the output stream information. This
> basically means that for V4L2 restriction, you'd have to bounce the
> buffers on frame size boundary or something like thisé
> 
> This workflow is very similar to how OMX works, but V4L2 is even less
> flexible on allocation vs format, forcing more re-allocation.

Oh, actually, you already bounce the buffers through the color
converter, so I guess this can all be hidden internally.

> 
> > regards
> > Philipp