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media: Documentation: Initialisation finishes before subdev registration

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Document that sub-device initialisation needs to complete before the async
sub-device is registered as there is no further driver action needed
before the sensor becomes accessible via the UAPI.

Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
This commit is contained in:
Sakari Ailus 2023-11-01 10:00:05 +02:00 committed by Hans Verkuil
parent 0e7f68fe16
commit 6a6e49f892
2 changed files with 9 additions and 1 deletions
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3
Documentation/driver-api/media/camera-sensor.rst
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@ -60,7 +60,8 @@ management over the pipeline.
Camera sensor drivers are responsible for controlling the power state of the
device they otherwise control as well. They shall use runtime PM to manage
power states. Runtime PM shall be enabled at probe time and disabled at remove
time. Drivers should enable runtime PM autosuspend.
time. Drivers should enable runtime PM autosuspend. Also see
:ref:`async sub-device registration <media-registering-async-subdevs>`.
The runtime PM handlers shall handle clocks, regulators, GPIOs, and other
system resources required to power the sensor up and down. For drivers that

7
Documentation/driver-api/media/v4l2-subdev.rst
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@ -181,6 +181,8 @@ You can unregister a sub-device using:
Afterwards the subdev module can be unloaded and
:c:type:`sd <v4l2_subdev>`->dev == ``NULL``.
.. _media-registering-async-subdevs:
Registering asynchronous sub-devices
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@ -195,6 +197,11 @@ performed using the :c:func:`v4l2_async_unregister_subdev` call. Subdevices
registered this way are stored in a global list of subdevices, ready to be
picked up by bridge drivers.
Drivers must complete all initialization of the sub-device before
registering it using :c:func:`v4l2_async_register_subdev`, including
enabling runtime PM. This is because the sub-device becomes accessible
as soon as it gets registered.
Asynchronous sub-device notifiers
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^