Re: [PATCH v3 5/5] media: v4l2-async: Create links during v4l2_async_match_notify()

[Jean-Michel Hautbois <jeanmichel.hautbois@xxxxxxxxx>]

Hi !

Thanks for the patch !

On 02/03/2022 23:03, Daniel Scally wrote:
> Upon an async fwnode match, there's some typical behaviour that the
> notifier and matching subdev will want to do. For example, a notifier
> representing a sensor matching to an async subdev representing its
> VCM will want to create an ancillary link to expose that relationship
> to userspace.
>
> To avoid lots of code in individual drivers, try to build these links
> within v4l2 core.
>
> Signed-off-by: Daniel Scally <djrscally@xxxxxxxxx>

Reviewed-by: Jean-Michel Hautbois <jeanmichel.hautbois@xxxxxxxxxxxxxxxx>

> ---
>
> Changes since v2:
>
> 	- Stopped checking the notifier entity's function when creating the new
> 	links, and just create them whenever the subdev entity's function is either
> 	a lens controller or a flash. (Sakari)
>
> Changes since v1:
>
> 	- Added #ifdef guards for CONFIG_MEDIA_CONTROLLER
> 	- Some spelling and nomenclature cleanup (Laurent)
>
> Changes since the rfc:
>
> 	- None
>
>   drivers/media/v4l2-core/v4l2-async.c | 31 ++++++++++++++++++++++++++++
>   1 file changed, 31 insertions(+)
>
> diff --git a/drivers/media/v4l2-core/v4l2-async.c b/drivers/media/v4l2-core/v4l2-async.c
> index 0404267f1ae4..436bd6900fd8 100644
> --- a/drivers/media/v4l2-core/v4l2-async.c
> +++ b/drivers/media/v4l2-core/v4l2-async.c
> @@ -275,6 +275,24 @@ v4l2_async_nf_try_complete(struct v4l2_async_notifier *notifier)
>   static int
>   v4l2_async_nf_try_all_subdevs(struct v4l2_async_notifier *notifier);
>   
> +static int v4l2_async_create_ancillary_links(struct v4l2_async_notifier *n,
> +					     struct v4l2_subdev *sd)
> +{
> +	struct media_link *link = NULL;
> +
> +#if IS_ENABLED(CONFIG_MEDIA_CONTROLLER)
> +
> +	if (sd->entity.function != MEDIA_ENT_F_LENS &&
> +	    sd->entity.function != MEDIA_ENT_F_FLASH)
> +		return 0;
> +
> +	link = media_create_ancillary_link(&n->sd->entity, &sd->entity);
> +
> +#endif
> +
> +	return IS_ERR(link) ? PTR_ERR(link) : 0;
> +}
> +
>   static int v4l2_async_match_notify(struct v4l2_async_notifier *notifier,
>   				   struct v4l2_device *v4l2_dev,
>   				   struct v4l2_subdev *sd,
> @@ -293,6 +311,19 @@ static int v4l2_async_match_notify(struct v4l2_async_notifier *notifier,
>   		return ret;
>   	}
>   
> +	/*
> +	 * Depending of the function of the entities involved, we may want to
> +	 * create links between them (for example between a sensor and its lens
> +	 * or between a sensor's source pad and the connected device's sink
> +	 * pad).
> +	 */
> +	ret = v4l2_async_create_ancillary_links(notifier, sd);
> +	if (ret) {
> +		v4l2_async_nf_call_unbind(notifier, sd, asd);
> +		v4l2_device_unregister_subdev(sd);
> +		return ret;
> +	}
> +
>   	/* Remove from the waiting list */
>   	list_del(&asd->list);
>   	sd->asd = asd;