Re: [PATCH v16 16/32] v4l: async: Allow async notifier register call succeed with no subdevs

[Sebastian Reichel <sre@xxxxxxxxxx>]

Hi,

On Thu, Oct 26, 2017 at 10:53:26AM +0300, 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>
> ---

Reviewed-by: Sebastian Reichel <sebastian.reichel@xxxxxxxxxxxxxxx>

-- Sebastian

>  drivers/media/v4l2-core/v4l2-async.c | 12 ++++++++++--
>  1 file changed, 10 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/media/v4l2-core/v4l2-async.c b/drivers/media/v4l2-core/v4l2-async.c
> index 46db85685894..1b536d68cedf 100644
> --- a/drivers/media/v4l2-core/v4l2-async.c
> +++ b/drivers/media/v4l2-core/v4l2-async.c
> @@ -180,14 +180,22 @@ int v4l2_async_notifier_register(struct v4l2_device *v4l2_dev,
>  	int ret;
>  	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(&notifier->waiting);
>  	INIT_LIST_HEAD(&notifier->done);
>  
> +	if (!notifier->num_subdevs) {
> +		int ret;
> +
> +		ret = v4l2_async_notifier_call_complete(notifier);
> +		notifier->v4l2_dev = NULL;
> +
> +		return ret;
> +	}
> +
>  	for (i = 0; i < notifier->num_subdevs; i++) {
>  		asd = notifier->subdevs[i];
>  
> -- 
> 2.11.0
>

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