Re: [PATCH v9 13/24] v4l: async: Allow async notifier register call succeed with no subdevs

Sakari Ailus
2017-09-11T08:21:40Z

On Mon, Sep 11, 2017 at 10:05:40AM +0200, Hans Verkuil wrote:
> On 09/08/2017 03:18 PM, Sakari Ailus wrote:
> > The information on how many async sub-devices would be bindable to a
> > notifier is typically dependent on information from platform firmware and
> > it's not driver's business to be aware of that.
> >
> > Many V4L2 main drivers are perfectly usable (and useful) without async
> > sub-devices and so if there aren't any around, just proceed call the
> > notifier's complete callback immediately without registering the notifier
> > itself.
> >
> > If a driver needs to check whether there are async sub-devices available,
> > it can be done by inspecting the notifier's num_subdevs field which tells
> > the number of async sub-devices.
> >
> > Signed-off-by: Sakari Ailus <sakari.ailus-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
> > ---
> > drivers/media/v4l2-core/v4l2-async.c | 6 ++++--
> > 1 file changed, 4 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/media/v4l2-core/v4l2-async.c b/drivers/media/v4l2-core/v4l2-async.c
> > index 7b396ff4302b..9ebc2e079d03 100644
> > --- a/drivers/media/v4l2-core/v4l2-async.c
> > +++ b/drivers/media/v4l2-core/v4l2-async.c
> > @@ -170,10 +170,12 @@ int v4l2_async_notifier_register(struct v4l2_device *v4l2_dev,
> > struct v4l2_async_subdev *asd;
> > int i;
> >
> > - if (!v4l2_dev || !notifier->num_subdevs ||
> > - notifier->num_subdevs > V4L2_MAX_SUBDEVS)
> > + if (!v4l2_dev || notifier->num_subdevs > V4L2_MAX_SUBDEVS)
> > return -EINVAL;
> >
> > + if (!notifier->num_subdevs)
> > + return v4l2_async_notifier_call_complete(notifier);
> > +
>
> I would move this 'if' down to after the next three lines...
>
> > notifier->v4l2_dev = v4l2_dev;
> > INIT_LIST_HEAD(&notifier->waiting);
> > INIT_LIST_HEAD(&notifier->done);
> >
>
> ...that way the notifier struct is properly initialized. Just in case anyone
> ever looks at these three fields.

Makes sense. Fixed.

--
Sakari Ailus
e-mail: sakari.ailus-X3B1VOXEql0@public.gmane.org
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