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Diffstat (limited to 'Documentation/driver-api/media/v4l2-subdev.rst')
| -rw-r--r-- | Documentation/driver-api/media/v4l2-subdev.rst | 51 |
1 files changed, 29 insertions, 22 deletions
diff --git a/Documentation/driver-api/media/v4l2-subdev.rst b/Documentation/driver-api/media/v4l2-subdev.rst index 327d444f34dc..eba5e4468282 100644 --- a/Documentation/driver-api/media/v4l2-subdev.rst +++ b/Documentation/driver-api/media/v4l2-subdev.rst @@ -206,60 +206,67 @@ of an unregister notifier, it must be cleaned up by calling Before registering the notifier, bridge drivers must do two things: first, the notifier must be initialized using the :c:func:`v4l2_async_nf_init`. Second, -bridge drivers can then begin to form a list of subdevice descriptors that the -bridge device needs for its operation. :c:func:`v4l2_async_nf_add_fwnode`, +bridge drivers can then begin to form a list of async connection descriptors +that the bridge device needs for its +operation. :c:func:`v4l2_async_nf_add_fwnode`, :c:func:`v4l2_async_nf_add_fwnode_remote` and :c:func:`v4l2_async_nf_add_i2c` -are available for that purpose. + +Async connection descriptors describe connections to external sub-devices the +drivers for which are not yet probed. Based on an async connection, a media data +or ancillary link may be created when the related sub-device becomes +available. There may be one or more async connections to a given sub-device but +this is not known at the time of adding the connections to the notifier. Async +connections are bound as matching async sub-devices are found, one by one. Asynchronous sub-device registration helper for camera sensor drivers ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ :c:func:`v4l2_async_register_subdev_sensor` is a helper function for sensor -drivers registering their own async sub-device, but it also registers a notifier -and further registers async sub-devices for lens and flash devices found in +drivers registering their own async connection, but it also registers a notifier +and further registers async connections for lens and flash devices found in firmware. The notifier for the sub-device is unregistered and cleaned up with the async sub-device, using :c:func:`v4l2_async_unregister_subdev`. Asynchronous sub-device notifier example ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ -These functions allocate an async sub-device descriptor which is of type struct -:c:type:`v4l2_async_subdev` embedded in a driver-specific struct. The &struct -:c:type:`v4l2_async_subdev` shall be the first member of this struct: +These functions allocate an async connection descriptor which is of type struct +:c:type:`v4l2_async_connection` embedded in a driver-specific struct. The &struct +:c:type:`v4l2_async_connection` shall be the first member of this struct: .. code-block:: c - struct my_async_subdev { - struct v4l2_async_subdev asd; + struct my_async_connection { + struct v4l2_async_connection asc; ... }; - struct my_async_subdev *my_asd; + struct my_async_connection *my_asc; struct fwnode_handle *ep; ... - my_asd = v4l2_async_nf_add_fwnode_remote(¬ifier, ep, - struct my_async_subdev); + my_asc = v4l2_async_nf_add_fwnode_remote(¬ifier, ep, + struct my_async_connection); fwnode_handle_put(ep); - if (IS_ERR(my_asd)) - return PTR_ERR(my_asd); + if (IS_ERR(my_asc)) + return PTR_ERR(my_asc); Asynchronous sub-device notifier callbacks ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ -The V4L2 core will then use these descriptors to match asynchronously -registered subdevices to them. If a match is detected the ``.bound()`` -notifier callback is called. After all subdevices have been located the -.complete() callback is called. When a subdevice is removed from the -system the .unbind() method is called. All three callbacks are optional. +The V4L2 core will then use these connection descriptors to match asynchronously +registered subdevices to them. If a match is detected the ``.bound()`` notifier +callback is called. After all connections have been bound the .complete() +callback is called. When a connection is removed from the system the +``.unbind()`` method is called. All three callbacks are optional. Drivers can store any type of custom data in their driver-specific -:c:type:`v4l2_async_subdev` wrapper. If any of that data requires special +:c:type:`v4l2_async_connection` wrapper. If any of that data requires special handling when the structure is freed, drivers must implement the ``.destroy()`` notifier callback. The framework will call it right before freeing the -:c:type:`v4l2_async_subdev`. +:c:type:`v4l2_async_connection`. Calling subdev operations ~~~~~~~~~~~~~~~~~~~~~~~~~ |