Re: [PATCH] media: rcar-vin: Update crop and compose settings for every s_fmt call

["Lad, Prabhakar" <prabhakar.csengg@gmail.com>]

Hi Laurent,

On Fri, Sep 4, 2020 at 3:25 AM Laurent Pinchart
<laurent.pinchart@ideasonboard.com> wrote:
>
> Hi Prabhakar,
>
> On Thu, Sep 03, 2020 at 03:53:18PM +0100, Lad, Prabhakar wrote:
> > On Wed, Aug 19, 2020 at 3:08 PM Hans Verkuil wrote:
> > > On 03/08/2020 21:21, Niklas wrote:
> > > > On 2020-08-03 19:11:32 +0100, Lad, Prabhakar wrote:
> > > >> On Sat, Aug 1, 2020 at 10:04 AM Niklas wrote:
> > > >>> On 2020-07-31 10:29:05 +0100, Lad Prabhakar wrote:
> > > >>>> The crop and compose settings for VIN in non mc mode werent updated
> > > >>>> in s_fmt call this resulted in captured images being clipped.
> > > >>>>
> > > >>>> With the below sequence on the third capture where size is set to
> > > >>>> 640x480 resulted in clipped image of size 320x240.
> > > >>>>
> > > >>>> high(640x480) -> low (320x240) -> high (640x480)
> > > >>>>
> > > >>>> This patch makes sure the VIN crop and compose settings are updated.
> > > >>>
> > > >>> This is clearly an inconsistency in the VIN driver that should be fixed.
> > > >>> But I think the none-mc mode implements the correct behavior. That is
> > > >>> that S_FMT should not modify the crop/compose rectangles other then make
> > > >>> sure they don't go out of bounds. This is an area we tried to clarify in
> > > >>> the past but I'm still not sure what the correct answer to.
> > > >>>
> > > >> What should be the exact behaviour of the bridge driver  for s_fmt
> > > >> call. Should the crop/compose settings be updated for every s_fmt
> > > >> callback or should they be only updated on s_selection callback.
> > > >> Currently the non-mc rcar-vin doesnt update the crop/compose setting
> > > >> in s_fmt callback due to which I see the above issue as mentioned.
> > > >
> > > > This is not entirely correct. It does update the crop and compose
> > > > rectangles on s_fmt, it makes sure they are not out-of-bounds for the
> > > > new format if it's accepted by s_fmt. See v4l2_rect_map_inside() calls
> > > > in the snippet bellow.
> > >
> > > For non-mc mode s_fmt must update any crop/compose rectangles to ensure that
> > > they are not out-of-bounds. But for mc mode the validation is done when you
> > > start streaming, so I think s_fmt won't make any changes in that mode.
> >
> > Thank you Hans.
> >
> > > Double-check that with Laurent, though...
> >
> > Niklas/Laurent - How do we proceed on this ?
>
> MC devices rely on userspace to propagate formats between entities, and
> on kernelspace to propagate formats within entities. This is documented
> in https://linuxtv.org/downloads/v4l-dvb-apis/userspace-api/v4l/dev-subdev.html.
> The configuration of an entity (formats and selection rectangles) must
> be valid at all times. Subdev drivers should thus either adjust or reset
> the crop and selection rectangles. The specification isn't clear on
> which behaviour should be implemented, the only related text is
>
> "Sub-devices that scale frames using variable scaling factors should
> reset the scale factors to default values when sink pads formats are
> modified. If the 1:1 scaling ratio is supported, this means that source
> pads formats should be reset to the sink pads formats."
>
> I would recommend resetting as the default behaviour. In any case,
> adjustements are needed to ensure that the configuration remains valid.
>
In that case can I have your Ack to the patch please.

Cheers,
Prabhakar