[media] media: Media Controller enable/disable source handler API

Add new fields to struct media_device to add enable_source, and
disable_source handlers, and source_priv to stash driver private
data that is used to run these handlers. The enable_source handler
finds source entity for the passed in entity and checks if it is
available. When link is found, it activates it. Disable source
handler deactivates the link.

Bridge driver is expected to implement and set these handlers.
Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

include/media/media-device.h

@@ -306,6 +306,11 @@ struct media_entity_notify {
  * @entity_notify: List of registered entity_notify callbacks
  * @lock:	Entities list lock
  * @graph_mutex: Entities graph operation lock
+ *
+ * @source_priv: Driver Private data for enable/disable source handlers
+ * @enable_source: Enable Source Handler function pointer
+ * @disable_source: Disable Source Handler function pointer
+ *
  * @link_notify: Link state change notification callback
  *
  * This structure represents an abstract high-level media device. It allows easy
@@ -317,6 +322,26 @@ struct media_entity_notify {
  *
  * @model is a descriptive model name exported through sysfs. It doesn't have to
  * be unique.
+ *
+ * @enable_source is a handler to find source entity for the
+ * sink entity  and activate the link between them if source
+ * entity is free. Drivers should call this handler before
+ * accessing the source.
+ *
+ * @disable_source is a handler to find source entity for the
+ * sink entity  and deactivate the link between them. Drivers
+ * should call this handler to release the source.
+ *
+ * Note: Bridge driver is expected to implement and set the
+ * handler when media_device is registered or when
+ * bridge driver finds the media_device during probe.
+ * Bridge driver sets source_priv with information
+ * necessary to run enable/disable source handlers.
+ *
+ * Use-case: find tuner entity connected to the decoder
+ * entity and check if it is available, and activate the
+ * the link between them from enable_source and deactivate
+ * from disable_source.
  */
 struct media_device {
 	/* dev->driver_data points to this struct. */
@@ -349,6 +374,11 @@ struct media_device {
 	/* Serializes graph operations. */
 	struct mutex graph_mutex;
 
+	void *source_priv;
+	int (*enable_source)(struct media_entity *entity,
+			     struct media_pipeline *pipe);
+	void (*disable_source)(struct media_entity *entity);
+
 	int (*link_notify)(struct media_link *link, u32 flags,
 			   unsigned int notification);
 };