On Thursday, January 27, 2011 13:30:30 Laurent Pinchart wrote: > 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@xxxxxxxxxxxxxxxx> > --- > Documentation/media-framework.txt | 13 ++++++++++ > drivers/media/media-device.c | 1 + > drivers/media/media-entity.c | 46 +++++++++++++++++++++++++++++++++++++ > include/media/media-device.h | 4 +++ > include/media/media-entity.h | 5 ++++ > 5 files changed, 69 insertions(+), 0 deletions(-) > > diff --git a/Documentation/media-framework.txt b/Documentation/media-framework.txt > index 88fe379..9017a41 100644 > --- a/Documentation/media-framework.txt > +++ b/Documentation/media-framework.txt > @@ -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. > diff --git a/drivers/media/media-device.c b/drivers/media/media-device.c > index b8a3ace..e4c2157 100644 > --- a/drivers/media/media-device.c > +++ b/drivers/media/media-device.c > @@ -73,6 +73,7 @@ int __must_check media_device_register(struct media_device *mdev) > mdev->entity_id = 1; > INIT_LIST_HEAD(&mdev->entities); > spin_lock_init(&mdev->lock); > + mutex_init(&mdev->graph_mutex); > > /* Register the device node. */ > mdev->devnode.fops = &media_device_fops; > diff --git a/drivers/media/media-entity.c b/drivers/media/media-entity.c > index a805f20..fe6bfd2 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 @@ 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 > */ > > diff --git a/include/media/media-device.h b/include/media/media-device.h > index 0b1ecf5..260d59c 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 @@ struct media_device { > > /* 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 b82f824..114541a 100644 > --- a/include/media/media-entity.h > +++ b/include/media/media-entity.h > @@ -81,6 +81,8 @@ struct media_entity { > struct media_pad *pads; /* Pads array (num_pads elements) */ > struct media_link *links; /* Links array (max_links elements)*/ > > + int use_count; /* Use count for the entity. */ Isn't unsigned better? > + > union { > /* Node specifications */ > struct { > @@ -129,6 +131,9 @@ 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 * > Regards, Hans -- Hans Verkuil - video4linux developer - sponsored by Cisco -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html