Re: [PATCH v5 38/39] media: imx: csi: fix crop rectangle reset in sink set_fmt

[Philipp Zabel]

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@1/60]"
media-ctl --set-v4l2 "'ipu1_csi0':2[fmt:AYUV32/960x540@1/30]"

Does this mean, it should work like this instead?

media-ctl --set-v4l2 "'ipu1_csi0_mux':2[fmt:UYVY2X8/1920x1080@1/60]"
media-ctl --set-v4l2 "'ipu1_csi0':0[fmt:UYVY2X8/1920x1080@1/60,compose:(0,0)/960x540]"
media-ctl --set-v4l2 "'ipu1_csi0':2[fmt:AYUV32/960x540@1/30]"

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

regards
Philipp