[media] media: Entity use count

Due to the wide differences between drivers regarding power management
needs, the media controller does not implement power management.
However, the media_entity structure includes a use_count field that
media drivers can use to track the number of users of every entity for
power management needs.

The use_count field is owned by media drivers and must not be touched by
entity drivers. Access to the field must be protected by the media
device graph_mutex lock.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/include/media/media-device.h b/include/media/media-device.h
index a8390fe87e83..5d2bff4fc9e0 100644
--- a/include/media/media-device.h
+++ b/include/media/media-device.h
@@ -25,6 +25,7 @@
 
 #include <linux/device.h>
 #include <linux/list.h>
+#include <linux/mutex.h>
 #include <linux/spinlock.h>
 
 #include <media/media-devnode.h>
@@ -42,6 +43,7 @@
  * @entity_id:  ID of the next entity to be registered
  * @entities:   List of registered entities
  * @lock:       Entities list lock
+ * @graph_mutex: Entities graph operation lock
  *
  * This structure represents an abstract high-level media device. It allows easy
  * access to entities and provides basic media device-level support. The
@@ -69,6 +71,8 @@ struct media_device {
 
         /* Protects the entities list */
         spinlock_t lock;
+        /* Serializes graph operations. */
+        struct mutex graph_mutex;
 };
 
 /* media_devnode to media_device */