Re: [PATCH] media: v4l2-subdev: Fix stream handling for crop API

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

On Tue, Apr 02, 2024 at 03:23:03PM +0000, Sakari Ailus wrote:
> On Tue, Apr 02, 2024 at 12:11:30PM +0300, Tomi Valkeinen wrote:
> > On 02/04/2024 11:46, Sakari Ailus wrote:
> > > On Tue, Apr 02, 2024 at 11:44:07AM +0300, Laurent Pinchart wrote:
> > > > On Tue, Apr 02, 2024 at 08:20:22AM +0000, Sakari Ailus wrote:
> > > > > Moi,
> > > > > 
> > > > > On Tue, Apr 02, 2024 at 02:37:25AM +0300, Laurent Pinchart wrote:
> > > > > > When support for streams was added to the V4L2 subdev API, the
> > > > > > v4l2_subdev_crop structure was extended with a stream field, but the
> > > > > > field was not handled in the core code that translates the
> > > > > > VIDIOC_SUBDEV_[GS]_CROP ioctls to the selection API. Fix it.
> > > > > 
> > > > > The field is indeed in the UAPI headers. But do we want to support the CROP
> > > > > IOCTL for streams? Shouldn't the callers be using the [GS]_SELECTION
> > > > > instead?
> > > > 
> > > > They should, but if the field is there, we should support it :-) The
> > > > alternative is to remove it. It will cause failures in v4l2-compliance
> > > > that we'll need to handle though.
> > > 
> > > I'd prefer to stick to selections here, this is new functionality so
> > > [GS]_CROP support isn't required. I don't have a strong opinion on the
> > > matter though.
> > 
> > Maybe it's easier to just support the stream field, instead of making
> > [GS]_CROP the odd case which looks like it should support streams, but then
> > doesn't...
> 
> It's an old IOCTL already replaced by the [GS]_SELECTION. I mainly write
> kernel space software but overall I think it's better if we can provide a
> single API for controlling cropping instead of two with similar
> functionality, of which the user then should choose from.
> 
> It should be also documented in this context if we choose support
> [GS]_CROP.
> 
> So I believe we have less work to do and have a better result if we just
> drop the stream field there. :-) 

I tend to agree, even if that's only a slight preference. Tomi, if
you're fine with this, I'll update the patch.

-- 
Regards,

Laurent Pinchart