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[media] media: Entity use count

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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
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9
include/media/media-entity.h
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@@ -81,6 +81,12 @@ struct media_entity {
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 @@ void media_entity_cleanup(struct media_entity *entity);
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 *