linux-kernel - Re: [PATCH v2] media: v4l2-subdev: Refactor events

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Message-ID: <ZxX2SVl/p0i7Nemi@tom-HP-ZBook-Fury-15-G7-Mobile-Workstation>
Date: Mon, 21 Oct 2024 08:35:53 +0200
From: Tommaso Merciai <tomm.merciai@...il.com>
To: Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc: sakari.ailus@...ux.intel.com,
	Mauro Carvalho Chehab <mchehab@...nel.org>,
	Hans Verkuil <hverkuil@...all.nl>,
	Tomi Valkeinen <tomi.valkeinen@...asonboard.com>,
	Paweł Anikiel <panikiel@...gle.com>,
	linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] media: v4l2-subdev: Refactor events

Hi Laurent,
Thanks for your review.

On Sun, Oct 20, 2024 at 07:43:54PM +0300, Laurent Pinchart wrote:
> Hi Tommaso,
> 
> Thank you for the patch.
> 
> On Sun, Oct 20, 2024 at 06:35:32PM +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.
> 
> I would add here
> 
> This simplifies subdev drivers by avoiding the need to set the
> V4L2_SUBDEV_FL_HAS_EVENTS flag and plug the event handlers, and ensures
> consistency of the API exposed to userspace.
> 
> And you can also add
> 
> Suggested-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>
> 
> > Signed-off-by: Tommaso Merciai <tomm.merciai@...il.com>
> 
> Reviewed-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>

Oks, Thanks again.

> 
> Now, can we simplify sensor drivers to drop the event handlers and the
> flag ? :-)

Yep, plan is add all to support v4l2_subdev_init_finalize()
Removing:

 .subscribe_event = v4l2_ctrl_subdev_subscribe_event,
 .unsubscribe_event = v4l2_event_subdev_unsubscribe,

if are used. And ofc V4L2_SUBDEV_FL_HAS_EVENTS.

Meanwhile I think I will send v3 with your
suggestions. :)

Thanks & Regards,
Tommaso

> 
> > ---
> > Changes since v1:
> >  - Aligned event subscription with unsubscription as suggested by LPinchart,
> >    SAilus
> > 
> >  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..fad8fa1f63e8 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;
> >  
> >  	case VIDIOC_UNSUBSCRIBE_EVENT:
> > -		return v4l2_subdev_call(sd, core, unsubscribe_event, vfh, arg);
> > +		if (v4l2_subdev_has_op(sd, core, unsubscribe_event))
> > +			return v4l2_subdev_call(sd, core, unsubscribe_event,
> > +						vfh, arg);
> > +
> > +		if (sd->flags & V4L2_SUBDEV_FL_HAS_EVENTS)
> > +			return v4l2_event_subdev_unsubscribe(sd, vfh, arg);
> > +
> > +		return -ENOIOCTLCMD;
> >  
> >  #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);
> 
> -- 
> Regards,
> 
> Laurent Pinchart