diff options
Diffstat (limited to 'Documentation/media-framework.txt')
| -rw-r--r-- | Documentation/media-framework.txt | 18 |
1 files changed, 11 insertions, 7 deletions
diff --git a/Documentation/media-framework.txt b/Documentation/media-framework.txt index b424de6c3bb3..7fbfe4bd1f47 100644 --- a/Documentation/media-framework.txt +++ b/Documentation/media-framework.txt @@ -101,14 +101,18 @@ include/media/media-entity.h. The structure is usually embedded into a higher-level structure, such as a v4l2_subdev or video_device instance, although drivers can allocate entities directly. -Drivers initialize entities by calling +Drivers initialize entity pads by calling - media_entity_init(struct media_entity *entity, u16 num_pads, + media_entity_pads_init(struct media_entity *entity, u16 num_pads, struct media_pad *pads); -The media_entity name, type, flags, revision and group_id fields can be -initialized before or after calling media_entity_init. Entities embedded in -higher-level standard structures can have some of those fields set by the +If no pads are needed, drivers could directly fill entity->num_pads +with 0 and entity->pads with NULL or to call the above function that +will do the same. + +The media_entity name, type, flags, revision and group_id fields should be +initialized before calling media_device_register_entity(). Entities embedded +in higher-level standard structures can have some of those fields set by the higher-level framework. As the number of pads is known in advance, the pads array is not allocated @@ -116,10 +120,10 @@ dynamically but is managed by the entity driver. Most drivers will embed the pads array in a driver-specific structure, avoiding dynamic allocation. Drivers must set the direction of every pad in the pads array before calling -media_entity_init. The function will initialize the other pads fields. +media_entity_pads_init. The function will initialize the other pads fields. Unlike the number of pads, the total number of links isn't always known in -advance by the entity driver. As an initial estimate, media_entity_init +advance by the entity driver. As an initial estimate, media_entity_pads_init pre-allocates a number of links equal to the number of pads. The links array will be reallocated if it grows beyond the initial estimate. |