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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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13
Documentation/media-framework.txt
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@@ -258,3 +258,16 @@ When the graph traversal is complete the function will return NULL.
Graph traversal can be interrupted at any moment. No cleanup function call is
required and the graph structure can be freed normally.
Use count and power handling
----------------------------
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.