Re: [PATCH v1 3/5] media: stm32-dcmipp: STM32 DCMIPP camera interface driver

Sakari Ailus
2023-08-24T12:37:05Z

Hi Alanin,

On Thu, Aug 24, 2023 at 01:09:34PM +0200, Alain Volmat wrote:
> Hi Sakari,
>
> thanks a lot for the review. I've already taken care of the comments I got
> from Dan and will also add fixes for your comments as well before
> pushing the v2. Before going into that I thought I'd better clarify the
> framerate part which seems the most tricky part.
>
> On Mon, Aug 07, 2023 at 09:29:55AM +0000, Sakari Ailus wrote:

...

> > > +static int dcmipp_byteproc_g_frame_interval(struct v4l2_subdev *sd,
> > > + struct v4l2_subdev_frame_interval *fi)
> > > +{
> > > + struct dcmipp_byteproc_device *byteproc = v4l2_get_subdevdata(sd);
> > > +
> > > + if (IS_SINK(fi->pad))
> > > + fi->interval = byteproc->sink_interval;
> > > + else
> > > + fi->interval = byteproc->src_interval;
> > > +
> > > + return 0;
> > > +}
> > > +
> > > +static int dcmipp_byteproc_s_frame_interval(struct v4l2_subdev *sd,
> > > + struct v4l2_subdev_frame_interval *fi)
> > > +{
> > > + struct dcmipp_byteproc_device *byteproc = v4l2_get_subdevdata(sd);
> > > +
> > > + mutex_lock(&byteproc->lock);
> > > +
> > > + if (byteproc->streaming) {
> > > + mutex_unlock(&byteproc->lock);
> > > + return -EBUSY;
> > > + }
> > > +
> > > + if (fi->interval.numerator == 0 || fi->interval.denominator == 0)
> > > + fi->interval = byteproc->sink_interval;
> > > +
> > > + if (IS_SINK(fi->pad)) {
> > > + /*
> > > + * Setting sink frame interval resets frame skipping.
> > > + * Sink frame interval is propagated to src.
> > > + */
> > > + byteproc->frate = 0;
> > > + byteproc->sink_interval = fi->interval;
> > > + byteproc->src_interval = byteproc->sink_interval;
> >
> > Is this used for anything else than configure skipping?
> >
> > I think I'd just have a control for it in that case.
> >
> > I don't think exposing frame interval configuration is necessarily even
> > meaningful for a device that just processes data but does not produce it.
>
> The DCMIPP is able to perform frame drop, 1/2, 1/4, 1/8 basically.
> As Dan pointed me out, indeed setting frame interval as we did on both
> sink and source pad isn't a defined behavior. I first thought that
> using the frame interval was the proper way to do that but that is
> indeed only used on producers such as sensors ....
> Which ctrl would you propose in such case ?

We don't have one, AFAIK, and I think it may be unlikely this will be
needed elsewhere. So I'd use a private control.

I wonder what others think. Cc Laurent as well.

--
Regards,

Sakari Ailus