media: entity: Add support for ancillary links

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

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

drivers/media/mc/mc-entity.c

@@ -1036,3 +1036,33 @@ 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,
+					       u32 flags)
+{
+	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 = flags | MEDIA_LNK_FL_ANCILLARY_LINK;
+
+	/* Initialize graph object embedded at 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);
+
+void media_remove_ancillary_link(struct media_link *link)
+{
+	list_del(&link->list);
+	media_gobj_destroy(&link->graph_obj);
+	kfree(link);
+}
+EXPORT_SYMBOL_GPL(media_remove_ancillary_link);

include/media/media-entity.h

@@ -1104,6 +1104,35 @@ void media_remove_intf_links(struct media_interface *intf);
  * it will issue a call to @operation\(@entity, @args\).
  */
 
+/**
+ * media_create_ancillary_link() - creates a link between two entities
+ *
+ * @primary:	pointer to the primary &media_entity
+ * @ancillary:	pointer to the ancillary &media_entity
+ * @flags:	Link flags, as defined in
+ *		:ref:`include/uapi/linux/media.h <media_header>`
+ *		( seek for ``MEDIA_LNK_FL_*``)
+ *
+ *
+ * Valid values for flags:
+ *
+ * %MEDIA_LNK_FL_ENABLED
+ *   Indicates that the two entities are connected pieces of hardware that form
+ *   a single logical unit.
+ *
+ *   A typical example is a camera lens being linked to the sensor that it is
+ *   supporting.
+ *
+ * %MEDIA_LNK_FL_IMMUTABLE
+ *   Indicates that the link enabled state can't be modified at runtime. If
+ *   %MEDIA_LNK_FL_IMMUTABLE is set, then %MEDIA_LNK_FL_ENABLED must also be
+ *   set, since an immutable link is always enabled.
+ */
+struct media_link *
+media_create_ancillary_link(struct media_entity *primary,
+			    struct media_entity *ancillary,
+			    u32 flags);
+
 #define media_entity_call(entity, operation, args...)			\
 	(((entity)->ops && (entity)->ops->operation) ?			\
 	 (entity)->ops->operation((entity) , ##args) : -ENOIOCTLCMD)