[v2,5/6] media: entity: Add support for ancillary links

Add functions to create ancillary links, so that they don't need to
be manually created by users.

Signed-off-by: Daniel Scally <djrscally@gmail.com>
---

Changes since v1:

	- Hardcoded MEDIA_LINK_FL_IMMUTABLE and MEDIA_LINK_FL_ENABLED (Laurent)

Changes since the rfc:

	- (Laurent) Set gobj0 and gobj1 directly instead of the other union
	members
	- (Laurent) Added MEDIA_LNK_FL_IMMUTABLE to the kerneldoc for the new
	create function

 drivers/media/mc/mc-entity.c | 22 ++++++++++++++++++++++
 include/media/media-entity.h | 21 +++++++++++++++++++++
 2 files changed, 43 insertions(+)

Hi Dan,

Thank you for the patch.

On Sun, Jan 30, 2022 at 11:58:20PM +0000, Daniel Scally wrote:
> Add functions to create ancillary links, so that they don't need to
> be manually created by users.
> 
> Signed-off-by: Daniel Scally <djrscally@gmail.com>
> ---
> 
> Changes since v1:
> 
> 	- Hardcoded MEDIA_LINK_FL_IMMUTABLE and MEDIA_LINK_FL_ENABLED (Laurent)
> 
> Changes since the rfc:
> 
> 	- (Laurent) Set gobj0 and gobj1 directly instead of the other union
> 	members
> 	- (Laurent) Added MEDIA_LNK_FL_IMMUTABLE to the kerneldoc for the new
> 	create function
> 
>  drivers/media/mc/mc-entity.c | 22 ++++++++++++++++++++++
>  include/media/media-entity.h | 21 +++++++++++++++++++++
>  2 files changed, 43 insertions(+)
> 
> diff --git a/drivers/media/mc/mc-entity.c b/drivers/media/mc/mc-entity.c
> index 29d1285c805a..7bf2c73a3886 100644
> --- a/drivers/media/mc/mc-entity.c
> +++ b/drivers/media/mc/mc-entity.c
> @@ -1050,3 +1050,25 @@ void media_remove_intf_links(struct media_interface *intf)
>  	mutex_unlock(&mdev->graph_mutex);
>  }
>  EXPORT_SYMBOL_GPL(media_remove_intf_links);
> +
> +struct media_link *media_create_ancillary_link(struct media_entity *primary,
> +					       struct media_entity *ancillary)
> +{
> +	struct media_link *link;
> +
> +	link = media_add_link(&primary->links);
> +	if (!link)
> +		return ERR_PTR(-ENOMEM);
> +
> +	link->gobj0 = &primary->graph_obj;
> +	link->gobj1 = &ancillary->graph_obj;
> +	link->flags = MEDIA_LNK_FL_IMMUTABLE | MEDIA_LNK_FL_ENABLED |
> +		      MEDIA_LNK_FL_ANCILLARY_LINK;
> +
> +	/* Initialize graph object embedded in the new link */
> +	media_gobj_create(primary->graph_obj.mdev, MEDIA_GRAPH_LINK,
> +			  &link->graph_obj);
> +
> +	return link;
> +}
> +EXPORT_SYMBOL_GPL(media_create_ancillary_link);
> diff --git a/include/media/media-entity.h b/include/media/media-entity.h
> index fea489f03d57..afeda41ece4c 100644
> --- a/include/media/media-entity.h
> +++ b/include/media/media-entity.h
> @@ -1104,6 +1104,27 @@ void media_remove_intf_links(struct media_interface *intf);
>   * it will issue a call to @operation\(@entity, @args\).
>   */
>  
> +/**
> + * media_create_ancillary_link() - create an ancillary link between two
> + *				   instances of &media_entity
> + *
> + * @primary:	pointer to the primary &media_entity
> + * @ancillary:	pointer to the ancillary &media_entity
> + *
> + * Create an ancillary link between two entities, indicating that they
> + * represent two connected pieces of hardware that form a single logical unit.

Here you say logical unit, while in patch 3/6 you use the term "physical
relationship". I think I'd go for "logical" there too.

> + * A typical example is a camera lens being linked to the sensor that it is

s/lens/lens controller/

> + * supporting.
> + *
> + * The function sets both MEDIA_LNK_FL_ENABLED and MEDIA_LNK_FL_IMMUTABLE for
> + * the new link. This behaviour may be subject to change in the future, so
> + * userspace applications using ancillary links should ensure that ancillary
> + * links are enabled when in use.

I'd drop the last two lines as this is kernel documentation, not
userspace documentation.

> + */
> +struct media_link *
> +media_create_ancillary_link(struct media_entity *primary,
> +			    struct media_entity *ancillary);

As reported by the kernel buildbot, this should go after
media_entity_call().

> +
>  #define media_entity_call(entity, operation, args...)			\
>  	(((entity)->ops && (entity)->ops->operation) ?			\
>  	 (entity)->ops->operation((entity) , ##args) : -ENOIOCTLCMD)