Re: [PATCH] media: i2c: ov5645: add HAS_EVENTS supporty

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

Hi Tommaso,

On Tue, Oct 15, 2024 at 06:37:58PM +0200, Tommaso Merciai wrote:
> On Tue, Oct 15, 2024 at 08:16:13AM +0200, Tommaso Merciai wrote:
> > On Mon, Oct 14, 2024 at 08:54:52PM +0300, Laurent Pinchart wrote:
> > > On Mon, Oct 14, 2024 at 07:38:40PM +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 support: flag and .(un)subscribe_event().
> > > > 
> > > > Signed-off-by: Tommaso Merciai <tomm.merciai@gmail.com>
> > > > ---
> > > >  drivers/media/i2c/ov5645.c | 10 +++++++++-
> > > >  1 file changed, 9 insertions(+), 1 deletion(-)
> > > > 
> > > > diff --git a/drivers/media/i2c/ov5645.c b/drivers/media/i2c/ov5645.c
> > > > index 0c32bd2940ec..2c5145d5c616 100644
> > > > --- a/drivers/media/i2c/ov5645.c
> > > > +++ b/drivers/media/i2c/ov5645.c
> > > > @@ -29,6 +29,7 @@
> > > >  #include <linux/slab.h>
> > > >  #include <linux/types.h>
> > > >  #include <media/v4l2-ctrls.h>
> > > > +#include <media/v4l2-event.h>
> > > >  #include <media/v4l2-fwnode.h>
> > > >  #include <media/v4l2-subdev.h>
> > > >  
> > > > @@ -1034,6 +1035,11 @@ static const struct v4l2_subdev_video_ops ov5645_video_ops = {
> > > >  	.s_stream = ov5645_s_stream,
> > > >  };
> > > >  
> > > > +static const struct v4l2_subdev_core_ops ov5645_subdev_core_ops = {
> > > > +	.subscribe_event = v4l2_ctrl_subdev_subscribe_event,
> > > > +	.unsubscribe_event = v4l2_event_subdev_unsubscribe,
> > > > +};
> > > > +
> > > >  static const struct v4l2_subdev_pad_ops ov5645_subdev_pad_ops = {
> > > >  	.enum_mbus_code = ov5645_enum_mbus_code,
> > > >  	.enum_frame_size = ov5645_enum_frame_size,
> > > > @@ -1043,6 +1049,7 @@ static const struct v4l2_subdev_pad_ops ov5645_subdev_pad_ops = {
> > > >  };
> > > >  
> > > >  static const struct v4l2_subdev_ops ov5645_subdev_ops = {
> > > > +	.core = &ov5645_subdev_core_ops,
> > > >  	.video = &ov5645_video_ops,
> > > >  	.pad = &ov5645_subdev_pad_ops,
> > > >  };
> > > > @@ -1178,7 +1185,8 @@ static int ov5645_probe(struct i2c_client *client)
> > > >  
> > > >  	v4l2_i2c_subdev_init(&ov5645->sd, client, &ov5645_subdev_ops);
> > > >  	ov5645->sd.internal_ops = &ov5645_internal_ops;
> > > > -	ov5645->sd.flags |= V4L2_SUBDEV_FL_HAS_DEVNODE;
> > > > +	ov5645->sd.flags |= V4L2_SUBDEV_FL_HAS_DEVNODE |
> > > > +			    V4L2_SUBDEV_FL_HAS_EVENTS;
> > > 
> > > Instead of patching every subdev driver, should we handle all of this in
> > > the subdev core ? If a control handler is set for the subdev, we could
> > > set the HAS_EVENTS flag automatically, and default to
> > > v4l2_ctrl_subdev_subscribe_event() and v4l2_event_subdev_unsubscribe()
> > > if there are no control operations.
> 
> Premit:
>  - Don't know if I'm wrong eh.

Nobody knows :-)

> This can be done into:
> 
> __v4l2_subdev_init_finalize()
> 
> Adding:
> 
> 	if (sd->ctrl_handler)
> 		sd->flags |= V4L2_SUBDEV_FL_HAS_EVENTS;
> 
> And check if there are no control operations using:
> 
> bool has_subscribe_event;
> bool has_unsubscribe_event;
> 
> 
> has_subscribe_event = v4l2_subdev_has_op(sd, core, subscribe_event);
> has_unsubscribe_event = v4l2_subdev_has_op(sd, core, unsubscribe_event);
> 
> if (!has_subscribe_event)
> 	assign v4l2_ctrl_subdev_subscribe_event as default .subscribe ops(somehow)

We can't change the ops structure as it's constant. Something like this
could do:

diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
index 3a4ba08810d2..41ae18a0d41e 100644
--- a/drivers/media/v4l2-core/v4l2-subdev.c
+++ b/drivers/media/v4l2-core/v4l2-subdev.c
@@ -691,10 +691,24 @@ 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);
+		else if ((sd->flags & V4L2_SUBDEV_FL_HAS_EVENTS) &&
+			 vfh->ctrl_handler)
+			return v4l2_ctrl_subdev_subscribe_event(sd, vfh, arg);
+		else
+			return -ENOIOCTLCMD;

 	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);
+		else
+			return v4l2_event_subdev_unsubscribe(sd, vfh, sub);

 #ifdef CONFIG_VIDEO_ADV_DEBUG
 	case VIDIOC_DBG_G_REGISTER:

> if (!has_unsubscribe_event)
> 	assign v4l2_event_subdev_unsubscribe as default .unsubscribe ops (somehow)
> 
> 
> Or maybe v4l2_subdev_init_finalize() it's too late?
> I'm completely wrong? What do you think?

I like v4l2_subdev_init_finalize() as we're pushing all subdev drivers
to use it, so it's an extra incentive.

> > Well :)
> > Not every subdev drivers, but only the ones I'm testing.
> > 
> > Yesterday I was playing with ov5645 :) And I got:
> > 
> > v4l2-compliance -d /dev/v4l-subdev1
> > 
> > test VIDIOC_G/S/TRY_EXT_CTRLS: OK
> > fail: v4l2-test-controls.cpp(1108): subscribe event for control 'User Controls' failed
> > 
> > Joke apart fully agree and thanks for your hint!
> > I will take  a look :)
> > 
> > > >  	ov5645->pad.flags = MEDIA_PAD_FL_SOURCE;
> > > >  	ov5645->sd.dev = &client->dev;
> > > >  	ov5645->sd.entity.function = MEDIA_ENT_F_CAM_SENSOR;

-- 
Regards,

Laurent Pinchart