Re: [PATCH v4] media: rcar-isp: Add Renesas R-Car Image Signal Processor driver

["Niklas Söderlund" <niklas.soderlund+renesas@ragnatech.se>]

Hej Sakari,

On 2021-07-28 20:03:37 +0300, Sakari Ailus wrote:
> Hej Niklas,
> 
> On Tue, Jul 27, 2021 at 07:55:49PM +0200, Niklas Söderlund wrote:
> ...
> > > > > > +static const struct v4l2_subdev_pad_ops risp_pad_ops = {
> > > > > > +	.set_fmt = risp_set_pad_format,
> > > > > > +	.get_fmt = risp_get_pad_format,
> > > > > 
> > > > > Maybe set link_validate to v4l2_subdev_link_validate_default?
> > > > 
> > > > I thought about that but with the multiplexed stream issue I thought it 
> > > > best to not to add that yet. Do you think this make sens?
> > > 
> > > What would be the alternative? Without that, there's no guarantee
> > > whatsoever what the input is. It may also enable writing user space that
> > > breaks after fixing this in the driver.
> > 
> > We still still don't have any guarantees whatsoever as we can only 
> > describe and validate one stream.
> > 
> > > 
> > > Where in the pipeline would you have multiple streams over a single data
> > > path?
> > 
> > On Gen3 platforms without an ISP we have it on the rcar-csi2 sink pad 
> > and on Gen3 platforms with an ISP we have it on the rcar-isp sink pad.  
> > In both cases it's the IP block that separates the CSI-2 buss to the 
> > different capture engines.
> 
> Ok. In this case the driver may be better merged to the staging tree or
> labelled experimental as its UAPI isn't stable. I wonder what Hans thinks.

Marking it experimental maybe a good idea or only allowing one stream on 
the CSI-2 bus. Then we could use v4l2_subdev_link_validate_default and 
validate the link pad format, I will do so in the next version.

> 
> -- 
> Kind regards,
> 
> Sakari Ailus

-- 
Regards,
Niklas Söderlund