linux-kernel - Re: [PATCH v5 38/39] media: imx: csi: fix crop rectangle reset in sink set

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Date:   Mon, 20 Mar 2017 15:00:51 +0100
From:   Philipp Zabel <p.zabel@...gutronix.de>
To:     Russell King - ARM Linux <linux@...linux.org.uk>
Cc:     Steve Longerbeam <slongerbeam@...il.com>, robh+dt@...nel.org,
        mark.rutland@....com, shawnguo@...nel.org, kernel@...gutronix.de,
        fabio.estevam@....com, mchehab@...nel.org, hverkuil@...all.nl,
        nick@...anahar.org, markus.heiser@...marIT.de,
        laurent.pinchart+renesas@...asonboard.com, bparrot@...com,
        geert@...ux-m68k.org, arnd@...db.de, sudipm.mukherjee@...il.com,
        minghsiu.tsai@...iatek.com, tiffany.lin@...iatek.com,
        jean-christophe.trotin@...com, horms+renesas@...ge.net.au,
        niklas.soderlund+renesas@...natech.se, robert.jarzmik@...e.fr,
        songjun.wu@...rochip.com, andrew-ct.chen@...iatek.com,
        gregkh@...uxfoundation.org, shuah@...nel.org,
        sakari.ailus@...ux.intel.com, pavel@....cz,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-media@...r.kernel.org,
        devel@...verdev.osuosl.org,
        Steve Longerbeam <steve_longerbeam@...tor.com>
Subject: Re: [PATCH v5 38/39] media: imx: csi: fix crop rectangle reset in
 sink set_fmt

On Mon, 2017-03-20 at 12:08 +0000, Russell King - ARM Linux wrote:
> On Mon, Mar 20, 2017 at 12:55:26PM +0100, Philipp Zabel wrote:
> > The above paragraph suggests we skip any rectangles that are not
> > supported. In our case that would be 3. and 4., since the CSI can't
> > compose into a larger frame. I hadn't realised that the crop selection
> > currently happens on the source pad.
> 
> I'd recommend viewing the documentation in its post-processed version,
> because then you get the examples as pictures, and they say that a
> picture is worth 1000 words.  See
> 
>   https://linuxtv.org/downloads/v4l-dvb-apis/uapi/v4l/dev-subdev.html
> 
> There is almost an exact example of what we're trying to do - it's
> figure 4.6.  Here, we have a sink pad with a cropping rectangle on
> the input, which is then scaled to a composition rectangle (there's
> no bounds rectangle, and it's specified that in such a case the
> top,left of the composition rectangle will always be 0,0 - see quote
> below).
> 
> Where it differs is that the example also supports source cropping
> for two source pads.  We don't support that.
>
> The same document says:
> 
>   Scaling support is optional. When supported by a subdev, the crop
>   rectangle on the subdev's sink pad is scaled to the size configured
>   using the
>   :ref:`VIDIOC_SUBDEV_S_SELECTION <VIDIOC_SUBDEV_G_SELECTION>` IOCTL
>   using ``V4L2_SEL_TGT_COMPOSE`` selection target on the same pad. If the
>   subdev supports scaling but not composing, the top and left values are
>   not used and must always be set to zero.

Right, this sentence does imply that when scaling is supported, there
must be a sink compose rectangle, even when composing is not.

I have previously set up scaling like this:

media-ctl --set-v4l2 "'ipu1_csi0_mux':2[fmt:UYVY2X8/1920x1080@...0]"
media-ctl --set-v4l2 "'ipu1_csi0':2[fmt:AYUV32/960x540@...0]"

Does this mean, it should work like this instead?

media-ctl --set-v4l2 "'ipu1_csi0_mux':2[fmt:UYVY2X8/1920x1080@...0]"
media-ctl --set-v4l2 "'ipu1_csi0':0[fmt:UYVY2X8/1920x1080@...0,compose:(0,0)/960x540]"
media-ctl --set-v4l2 "'ipu1_csi0':2[fmt:AYUV32/960x540@...0]"

I suppose setting the source pad format should not be allowed to modify
the sink compose rectangle.

regards
Philipp