[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>
diff --git a/include/media/media-device.h b/include/media/media-device.h
index a8390fe..5d2bff4 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 @@
/* Protects the entities list */
spinlock_t lock;
+ /* Serializes graph operations. */
+ struct mutex graph_mutex;
};
/* media_devnode to media_device */
diff --git a/include/media/media-entity.h b/include/media/media-entity.h
index 28f61f6..a9b31d9 100644
--- a/include/media/media-entity.h
+++ b/include/media/media-entity.h
@@ -81,6 +81,12 @@
struct media_pad *pads; /* Pads array (num_pads elements) */
struct media_link *links; /* Links array (max_links elements)*/
+ /* Reference counts must never be negative, but are signed integers on
+ * purpose: a simple WARN_ON(<0) check can be used to detect reference
+ * count bugs that would make them negative.
+ */
+ int use_count; /* Use count for the entity. */
+
union {
/* Node specifications */
struct {
@@ -129,6 +135,9 @@
int media_entity_create_link(struct media_entity *source, u16 source_pad,
struct media_entity *sink, u16 sink_pad, u32 flags);
+struct media_entity *media_entity_get(struct media_entity *entity);
+void media_entity_put(struct media_entity *entity);
+
void media_entity_graph_walk_start(struct media_entity_graph *graph,
struct media_entity *entity);
struct media_entity *
