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

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Message-ID: <ZxYNCmZhGTICDfDC@tom-HP-ZBook-Fury-15-G7-Mobile-Workstation>
Date: Mon, 21 Oct 2024 10:12:58 +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

On Mon, Oct 21, 2024 at 10:30:34AM +0300, Laurent Pinchart wrote:
> On Mon, Oct 21, 2024 at 08:35:53AM +0200, Tommaso Merciai wrote:
> > 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.
> 
> What I meant is looking at the I2C sensor drivers that currently
> 
> - call v4l2_subdev_init_finalize()
> - set V4L2_SUBDEV_FL_HAS_EVENTS
> - set the .subscribe_event() and .unsubscribe_event() handlers
> 
> and dropping the flag and handlers from them. Is that what you plan to
> work on ?

Yep, I will take a look on that. :)

Thanks & Regards,
Tommaso

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