lk/linux-kernel-test
1
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity

[media] media: Entity use count

Browse Source 
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>
This commit is contained in:
Laurent Pinchart
2010-03-07 15:04:59 -03:00
committed by Mauro Carvalho Chehab
parent a5ccc48a7c
commit 503c3d829e
5 changed files with 73 additions and 0 deletions
Download Patch File Download Diff File Expand all files Collapse all files

46
drivers/media/media-entity.c
View File

@@ -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
@@ -195,6 +196,51 @@ media_entity_graph_walk_next(struct media_entity_graph *graph)
}
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
*/