Re: [PATCH] media: v4l2-subdev: Refactor events

[Tommaso Merciai]

Hi Sakari,

On Fri, Oct 18, 2024 at 07:30:30PM +0000, Sakari Ailus wrote:
> Hi Tommaso,
> 
> Thanks for working on this.

In real it's a Laurent's suggestion :)

> 
> On Fri, Oct 18, 2024 at 07:11:03PM +0200, Tommaso Merciai wrote:
> > Controls can be exposed to userspace via a v4l-subdevX device, and
> > userspace has to be able to subscribe to control events so that it is
> > notified when the control changes value.
> > If a control handler is set for the subdev then set the HAS_EVENTS
> > flag automatically into v4l2_subdev_init_finalize() and use
> > v4l2_ctrl_subdev_subscribe_event() and v4l2_event_subdev_unsubscribe()
> > as default if subdev don't have .(un)subscribe control operations.
> > 
> > Signed-off-by: Tommaso Merciai <tomm.merciai@xxxxxxxxx>
> > ---
> >  drivers/media/v4l2-core/v4l2-subdev.c | 22 ++++++++++++++++++++--
> >  1 file changed, 20 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
> > index 3a4ba08810d2..77ca829b9983 100644
> > --- a/drivers/media/v4l2-core/v4l2-subdev.c
> > +++ b/drivers/media/v4l2-core/v4l2-subdev.c
> > @@ -691,10 +691,25 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg,
> >  		return v4l2_event_dequeue(vfh, arg, file->f_flags & O_NONBLOCK);
> >  
> >  	case VIDIOC_SUBSCRIBE_EVENT:
> > -		return v4l2_subdev_call(sd, core, subscribe_event, vfh, arg);
> > +		if (v4l2_subdev_has_op(sd, core, subscribe_event))
> > +			return v4l2_subdev_call(sd, core, subscribe_event,
> > +						vfh, arg);
> > +
> > +		if ((sd->flags & V4L2_SUBDEV_FL_HAS_EVENTS) &&
> > +		     vfh->ctrl_handler)
> > +			return v4l2_ctrl_subdev_subscribe_event(sd, vfh, arg);
> > +
> > +		return -ENOIOCTLCMD;
> 
> While this mostly does the same thing, I prefer the order of tests below.
> Could you align event subscription with unsubscription?

What about:

	case VIDIOC_SUBSCRIBE_EVENT:
		if (!(sd->flags & V4L2_SUBDEV_FL_HAS_EVENTS))
			return -ENOIOCTLCMD;

		if (v4l2_subdev_has_op(sd, core, subscribe_event))
			return v4l2_subdev_call(sd, core, subscribe_event,
						vfh, arg);

		if (!vfh->ctrl_handler)
			return -ENOTTY;

		return v4l2_ctrl_subdev_subscribe_event(sd, vfh, arg);

	case VIDIOC_UNSUBSCRIBE_EVENT:
		if (!(sd->flags & V4L2_SUBDEV_FL_HAS_EVENTS))
			return -ENOIOCTLCMD;

		if (v4l2_subdev_has_op(sd, core, unsubscribe_event))
			return v4l2_subdev_call(sd, core, unsubscribe_event,
						vfh, arg);

		return v4l2_event_subdev_unsubscribe(sd, vfh, arg);

?

Thanks & Regards,
Tommaso

> 
> >  
> >  	case VIDIOC_UNSUBSCRIBE_EVENT:
> > -		return v4l2_subdev_call(sd, core, unsubscribe_event, vfh, arg);
> > +		if (!(sd->flags & V4L2_SUBDEV_FL_HAS_EVENTS))
> > +			return -ENOIOCTLCMD;
> > +
> > +		if (v4l2_subdev_has_op(sd, core, unsubscribe_event))
> > +			return v4l2_subdev_call(sd, core, unsubscribe_event,
> > +						vfh, arg);
> > +
> > +		return v4l2_event_subdev_unsubscribe(sd, vfh, arg);
> >  
> >  #ifdef CONFIG_VIDEO_ADV_DEBUG
> >  	case VIDIOC_DBG_G_REGISTER:
> > @@ -1641,6 +1656,9 @@ int __v4l2_subdev_init_finalize(struct v4l2_subdev *sd, const char *name,
> >  		}
> >  	}
> >  
> > +	if (sd->ctrl_handler)
> > +		sd->flags |= V4L2_SUBDEV_FL_HAS_EVENTS;
> > +
> >  	state = __v4l2_subdev_state_alloc(sd, name, key);
> >  	if (IS_ERR(state))
> >  		return PTR_ERR(state);
> 
> -- 
> Kind regards,
> 
> Sakari Ailus