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Diffstat (limited to 'Documentation/driver-api/media/mc-core.rst')
| -rw-r--r-- | Documentation/driver-api/media/mc-core.rst | 37 |
1 files changed, 28 insertions, 9 deletions
diff --git a/Documentation/driver-api/media/mc-core.rst b/Documentation/driver-api/media/mc-core.rst index 57b5bbba944e..400b8ca29367 100644 --- a/Documentation/driver-api/media/mc-core.rst +++ b/Documentation/driver-api/media/mc-core.rst @@ -42,9 +42,16 @@ Allocation of the structure is handled by the media device driver, usually by embedding the :c:type:`media_device` instance in a larger driver-specific structure. -Drivers register media device instances by calling -:c:func:`__media_device_register()` via the macro ``media_device_register()`` -and unregistered by calling :c:func:`media_device_unregister()`. +Drivers initialise media device instances by calling +:c:func:`media_device_init()`. After initialising a media device instance, it is +registered by calling :c:func:`__media_device_register()` via the macro +``media_device_register()`` and unregistered by calling +:c:func:`media_device_unregister()`. An initialised media device must be +eventually cleaned up by calling :c:func:`media_device_cleanup()`. + +Note that it is not allowed to unregister a media device instance that was not +previously registered, or clean up a media device instance that was not +previously initialised. Entities ^^^^^^^^ @@ -179,8 +186,9 @@ is required and the graph structure can be freed normally. Helper functions can be used to find a link between two given pads, or a pad connected to another pad through an enabled link -:c:func:`media_entity_find_link()` and -:c:func:`media_entity_remote_pad()`. +(:c:func:`media_entity_find_link()`, :c:func:`media_pad_remote_pad_first()`, +:c:func:`media_entity_remote_source_pad_unique()` and +:c:func:`media_pad_remote_pad_unique()`). Use count and power handling ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ @@ -206,18 +214,29 @@ Link properties can be modified at runtime by calling Pipelines and media streams ^^^^^^^^^^^^^^^^^^^^^^^^^^^ +A media stream is a stream of pixels or metadata originating from one or more +source devices (such as a sensors) and flowing through media entity pads +towards the final sinks. The stream can be modified on the route by the +devices (e.g. scaling or pixel format conversions), or it can be split into +multiple branches, or multiple branches can be merged. + +A media pipeline is a set of media streams which are interdependent. This +interdependency can be caused by the hardware (e.g. configuration of a second +stream cannot be changed if the first stream has been enabled) or by the driver +due to the software design. Most commonly a media pipeline consists of a single +stream which does not branch. + When starting streaming, drivers must notify all entities in the pipeline to prevent link states from being modified during streaming by calling :c:func:`media_pipeline_start()`. -The function will mark all entities connected to the given entity through -enabled links, either directly or indirectly, as streaming. +The function will mark all the pads which are part of the pipeline as streaming. The struct media_pipeline instance pointed to by -the pipe argument will be stored in every entity in the pipeline. +the pipe argument will be stored in every pad in the pipeline. Drivers should embed the struct media_pipeline in higher-level pipeline structures and can then access the -pipeline through the struct media_entity +pipeline through the struct media_pad pipe field. Calls to :c:func:`media_pipeline_start()` can be nested. |