On 09/12/17 10:42, 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@xxxxxxxxxxxxxxx>
Acked-by: Hans Verkuil <hans.verkuil@xxxxxxxxx>
Regards,
Hans
> ---
> 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..4525b03d59c1 100644
> --- a/drivers/media/v4l2-core/v4l2-async.c
> +++ b/drivers/media/v4l2-core/v4l2-async.c
> @@ -170,14 +170,16 @@ 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;
>
> notifier->v4l2_dev = v4l2_dev;
> INIT_LIST_HEAD(¬ifier->waiting);
> INIT_LIST_HEAD(¬ifier->done);
>
> + if (!notifier->num_subdevs)
> + return v4l2_async_notifier_call_complete(notifier);
> +
> for (i = 0; i < notifier->num_subdevs; i++) {
> asd = notifier->subdevs[i];
>
>
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