kernel/linux.git/Documentation/driver-api/media, branch v6.1.168

media: mc: entity: Rewrite media_pipeline_start()

2022-09-24T07:19:42+00:00

[Note: the code is mostly from Laurent but the patch description is from Tomi] The media_pipeline_start() and media_pipeline_stop() functions use the media graph walk API to traverse the graph and validate the pipeline. The graph walk traverses the media graph following links between the entities. Also, while the pipeline can't change between the start and stop calls, the graph is walked again from scratch at stop time, or any time a driver needs to inspect the pipeline. With the upcoming multiplexed streams support we will need a bit more intelligent pipeline construction, as e.g. two independent streams may be passing through a single entity via separate pads in which case those pads should not be part of the same pipeline. This patch essentially rewrites the media_pipeline_start/stop so that a pipeline is defined as a set of pads instead of entities and the media graph traversal considers the pad interdependencies when choosing which links to follow. Currently all the entity's pads are considered as interdependent. This means that the behavior with all the current drivers stays the same, but in the future we can define a more fine-grained pipeline construction. Additionally the media pipeline's pads are cached at media_pipeline_start() time, and re-used at media_pipeline_stop() which avoid the need to re-walk the whole graph as the previous implementation did. Also, caching pads in the pipeline can serve in the future as the foundation to provide a better API than the media graph walk to drivers to iterate over pads and entities in the pipeline. Note that the old media_pipeline_start/stop used the media graph walk API. The new version does not use the media graph walk API, but instead a new implementation. There are two reasons for not changing the graph walk: it proved to be rather difficult to change the graph walk to have the features implemented in this patch, and second, this keeps the backward compatibility of the graph walk as there are users of the graph walk API The long term plan is that all the existing code would be converted to use the new cached pipeline, thus allowing us to remove the graph walk. Signed-off-by: Laurent Pinchart Signed-off-by: Tomi Valkeinen Signed-off-by: Sakari Ailus Signed-off-by: Mauro Carvalho Chehab

media: Documentation: mc: add definitions for stream and pipeline

2022-09-24T07:07:24+00:00

The doc talks about streams and pipelines, but doesn't really define them. This is an attempt to define them according to my understanding. Signed-off-by: Tomi Valkeinen Reviewed-by: Laurent Pinchart Signed-off-by: Sakari Ailus Signed-off-by: Mauro Carvalho Chehab

media: avoid use of 'videobuf'

2022-08-29T14:27:18+00:00

The term 'videobuf' typically refers to the old videobuf version 1 framework. Avoid using this word in drivers that are converted to vb2. Signed-off-by: Hans Verkuil Signed-off-by: Mauro Carvalho Chehab

media: Documentation: mc-core: Fix typo

2022-07-27T18:25:37+00:00

Fix a typo in the mc-core.rst media driver API documentation. Due to its nature, the typo unfortunately caused a warning during documentation build. Fixes: 03b282861ca7 ("media: mc-entity: Add a new helper function to get a remote pad for a pad") Signed-off-by: Laurent Pinchart Signed-off-by: Hans Verkuil Signed-off-by: Mauro Carvalho Chehab

media: mc-entity: Add a new helper function to get a remote pad for a pad

2022-07-17T10:23:51+00:00

The newly added media_entity_remote_source_pad_unique() helper function handles use cases where the entity has a link enabled uniqueness constraint covering all pads. There are use cases where the constraint covers a specific pad only. Add a new media_pad_remote_pad_unique() function to handle this. It operates as media_entity_remote_source_pad_unique(), but on a given pad instead of on the entity. Signed-off-by: Laurent Pinchart Acked-by: Hans Verkuil Acked-by: Sakari Ailus Signed-off-by: Mauro Carvalho Chehab

media: mc-entity: Add a new helper function to get a remote pad

2022-07-17T10:23:10+00:00

The media_entity_remote_pad_first() helper function returns the first remote pad it finds connected to a given pad. Beside being possibly non-deterministic (as it stops at the first enabled link), the fact that it returns the first match makes it unsuitable for drivers that need to guarantee that a single link is enabled, for instance when an entity can process data from one of multiple sources at a time. For those use cases, add a new helper function, media_entity_remote_pad_unique(), that operates on an entity and returns a remote pad, with a guarantee that only one link is enabled. To ease its use in drivers, also add an inline wrapper that locates source pads specifically. A wrapper that locates sink pads can easily be added when needed. Signed-off-by: Laurent Pinchart Acked-by: Hans Verkuil Acked-by: Sakari Ailus Signed-off-by: Mauro Carvalho Chehab

media: mc-entity: Rename media_entity_remote_pad() to media_pad_remote_pad_first()

2022-07-17T10:21:35+00:00

The media_entity_remote_pad() is misnamed, as it operates on a pad and not an entity. Rename it to media_pad_remote_pad_first() to clarify its behaviour. Signed-off-by: Laurent Pinchart Reviewed-by: Hans Verkuil Acked-by: Sakari Ailus Signed-off-by: Mauro Carvalho Chehab

media: v4l2-async: Add notifier operation to destroy asd instances

2022-07-17T10:20:08+00:00

Drivers typically extend the v4l2_async_subdev structure by embedding it in a driver-specific structure, to store per-subdev custom data. The v4l2_async_subdev instances are freed by the v4l2-async framework, which makes this mechanism cumbersome to use safely when custom data needs special treatment to be destroyed (such as freeing additional memory, or releasing references to kernel objects). To ease this, add a .destroy() operation to the v4l2_async_notifier_operations structure. The operation is called right before the v4l2_async_subdev is freed, giving drivers a chance to destroy data if needed. Signed-off-by: Laurent Pinchart Reviewed-by: Hans Verkuil Acked-by: Sakari Ailus Signed-off-by: Mauro Carvalho Chehab

media: Documentation: mc: Add media_device_{init,cleanup}

2022-05-17T07:18:02+00:00

Document that drivers must first initialise a media device before registering it, and clean up once the media device is unregistered. Signed-off-by: Sakari Ailus Reviewed-by: Laurent Pinchart Signed-off-by: Mauro Carvalho Chehab

media: Documentation: add documentation about subdev state

2022-04-24T07:24:07+00:00

Add documentation about centrally managed subdev state. Signed-off-by: Tomi Valkeinen Reviewed-by: Jacopo Mondi Reviewed-by: Hans Verkuil Reviewed-by: Laurent Pinchart Signed-off-by: Sakari Ailus Signed-off-by: Mauro Carvalho Chehab