[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/drivers/media/media-entity.c b/drivers/media/media-entity.c
index 166f2b5..3e7e2d5 100644
--- a/drivers/media/media-entity.c
+++ b/drivers/media/media-entity.c
@@ -23,6 +23,7 @@
#include <linux/module.h>
#include <linux/slab.h>
#include <media/media-entity.h>
+#include <media/media-device.h>
/**
* media_entity_init - Initialize a media entity
@@ -196,6 +197,51 @@
EXPORT_SYMBOL_GPL(media_entity_graph_walk_next);
/* -----------------------------------------------------------------------------
+ * Module use count
+ */
+
+/*
+ * media_entity_get - Get a reference to the parent module
+ * @entity: The entity
+ *
+ * Get a reference to the parent media device module.
+ *
+ * The function will return immediately if @entity is NULL.
+ *
+ * Return a pointer to the entity on success or NULL on failure.
+ */
+struct media_entity *media_entity_get(struct media_entity *entity)
+{
+ if (entity == NULL)
+ return NULL;
+
+ if (entity->parent->dev &&
+ !try_module_get(entity->parent->dev->driver->owner))
+ return NULL;
+
+ return entity;
+}
+EXPORT_SYMBOL_GPL(media_entity_get);
+
+/*
+ * media_entity_put - Release the reference to the parent module
+ * @entity: The entity
+ *
+ * Release the reference count acquired by media_entity_get().
+ *
+ * The function will return immediately if @entity is NULL.
+ */
+void media_entity_put(struct media_entity *entity)
+{
+ if (entity == NULL)
+ return;
+
+ if (entity->parent->dev)
+ module_put(entity->parent->dev->driver->owner);
+}
+EXPORT_SYMBOL_GPL(media_entity_put);
+
+/* -----------------------------------------------------------------------------
* Links management
*/