[libcamera-devel] [PATCH v2 6/6] media: v4l2-async: Create links during v4l2_async_match_notify()

[Daniel Scally]

Hi Sakari

On 02/02/2022 16:38, Sakari Ailus wrote:
> Hi Daniel,
>
> Thanks for the update.
>
> On Sun, Jan 30, 2022 at 11:58:21PM +0000, 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 at gmail.com>
>> ---
>> 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 | 56 ++++++++++++++++++++++++++++
>>  1 file changed, 56 insertions(+)
>>
>> diff --git a/drivers/media/v4l2-core/v4l2-async.c b/drivers/media/v4l2-core/v4l2-async.c
>> index 0404267f1ae4..8980534e755e 100644
>> --- a/drivers/media/v4l2-core/v4l2-async.c
>> +++ b/drivers/media/v4l2-core/v4l2-async.c
>> @@ -275,6 +275,50 @@ 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_link(struct v4l2_async_notifier *notifier,
>> +				   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 -EINVAL;
>> +
>> +	link = media_create_ancillary_link(&notifier->sd->entity, &sd->entity);
>> +
>> +#endif
>> +
>> +	return IS_ERR(link) ? PTR_ERR(link) : 0;
>> +}
>> +
>> +/*
>> + * Create links on behalf of the notifier and subdev, where it's obvious what
>> + * should be done. At the moment, we only support cases where the notifier
>> + * is a camera sensor and the subdev is a lens controller.
> I think I'd rather change this so that ancillary links are created for lens
> and flash subdevs, independently of the function of the notifier subdev.
>
> Are there cases where this would go wrong currently, or in the future? I
> can't think of any right now at least. I guess we could add more
> information in the future to convey here if needed.
I don't think doing that would go wrong anyhow...at least not that I
could think of at the minute. My plan was to add a new function like
__v4l2_async_create_data_links() and call that (from
v4l2_async_try_create_links()) where the function of the notifier subdev
was MEDIA_ENT_F_VID_IF_BRIDGE...you think we shouldn't be doing that? Or
just that it should be separate?
>> + *
>> + * TODO: Create data links if the notifier's function is
>> + * MEDIA_ENT_F_VID_IF_BRIDGE and the subdev's is MEDIA_ENT_F_CAM_SENSOR.
>> + */
>> +static int v4l2_async_try_create_links(struct v4l2_async_notifier *notifier,
>> +				       struct v4l2_subdev *sd)
> How about calling this v4l2_async_create_ancillary_links()?


Sure

>
>> +{
>> +#if IS_ENABLED(CONFIG_MEDIA_CONTROLLER)
>> +
>> +	if (!notifier->sd)
>> +		return 0;
>> +
>> +	switch (notifier->sd->entity.function) {
>> +	case MEDIA_ENT_F_CAM_SENSOR:
>> +		return __v4l2_async_create_ancillary_link(notifier, sd);
>> +	}
>> +
>> +#endif
>> +	return 0;
>> +}
>> +
>>  static int v4l2_async_match_notify(struct v4l2_async_notifier *notifier,
>>  				   struct v4l2_device *v4l2_dev,
>>  				   struct v4l2_subdev *sd,
>> @@ -293,6 +337,18 @@ 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_try_create_links(notifier, sd);
>> +	if (ret) {
> The notifier's bound function has been called already. The unbound function
> needs to be thus called here, too.


Thank you, I'll do that in the next version

>
>> +		v4l2_device_unregister_subdev(sd);
>> +		return ret;
>> +	}
>> +
>>  	/* Remove from the waiting list */
>>  	list_del(&asd->list);
>>  	sd->asd = asd;