linux-kernel - Re: [PATCH 1/2] media: i2c: max96714: add HAS

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Message-ID: <20240912120510.GB25276@pendragon.ideasonboard.com>
Date: Thu, 12 Sep 2024 15:05:10 +0300
From: Laurent Pinchart <laurent.pinchart@...asonboard.com>
To: Tommaso Merciai <tomm.merciai@...il.com>
Cc: linuxfancy@...glegroups.com, sakari.ailus@...ux.intel.com,
	julien.massot@...labora.com,
	Mauro Carvalho Chehab <mchehab@...nel.org>,
	linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] media: i2c: max96714: add HAS_EVENTS subdev flag

On Thu, Sep 12, 2024 at 01:11:13PM +0200, Tommaso Merciai wrote:
> Hi Laurent,
> 
> On Thu, Sep 12, 2024 at 01:44:09PM +0300, Laurent Pinchart wrote:
> > Hi Tommaso,
> > 
> > On Tue, Sep 10, 2024 at 03:44:27PM +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. Add missing HAS_EVENTS flag.
> > 
> > How is this supposed to work, given that the driver doesn't implement
> > .subscribe_event() ?
> 
> You are completely right, sorry.
> I think in both cases I'm missing:
> 
> diff --git a/drivers/media/i2c/max96714.c b/drivers/media/i2c/max96714.c
> index 94b1bc000e48..2257b6b807ea 100644
> --- a/drivers/media/i2c/max96714.c
> +++ b/drivers/media/i2c/max96714.c
> @@ -17,6 +17,7 @@
> 
>  #include <media/v4l2-cci.h>
>  #include <media/v4l2-ctrls.h>
> +#include <media/v4l2-event.h>
>  #include <media/v4l2-fwnode.h>
>  #include <media/v4l2-subdev.h>
> 
> @@ -488,6 +489,8 @@ static int max96714_log_status(struct v4l2_subdev *sd)
> 
>  static const struct v4l2_subdev_core_ops max96714_subdev_core_ops = {
>         .log_status = max96714_log_status,
> +       .subscribe_event = v4l2_ctrl_subdev_subscribe_event,
> +       .unsubscribe_event = v4l2_event_subdev_unsubscribe,
>  };
> 
>  static const struct v4l2_subdev_video_ops max96714_video_ops = {
> 
> Like you suggest. Or I'm wrong?

That looks better :-)

Out of curiosity, what's your use case for control events ?

> > > Signed-off-by: Tommaso Merciai <tomm.merciai@...il.com>
> > > ---
> > >  drivers/media/i2c/max96714.c | 3 ++-
> > >  1 file changed, 2 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/media/i2c/max96714.c b/drivers/media/i2c/max96714.c
> > > index 159753b13777..94b1bc000e48 100644
> > > --- a/drivers/media/i2c/max96714.c
> > > +++ b/drivers/media/i2c/max96714.c
> > > @@ -602,7 +602,8 @@ static int max96714_create_subdev(struct max96714_priv *priv)
> > >  		goto err_free_ctrl;
> > >  	}
> > >  
> > > -	priv->sd.flags |= V4L2_SUBDEV_FL_HAS_DEVNODE | V4L2_SUBDEV_FL_STREAMS;
> > > +	priv->sd.flags |= V4L2_SUBDEV_FL_HAS_DEVNODE |
> > > +			  V4L2_SUBDEV_FL_HAS_EVENTS | V4L2_SUBDEV_FL_STREAMS;
> > >  	priv->sd.entity.function = MEDIA_ENT_F_VID_IF_BRIDGE;
> > >  	priv->sd.entity.ops = &max96714_entity_ops;
> > >  

-- 
Regards,

Laurent Pinchart