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media: Documentation: v4l: Add section titles for async

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Add section titles for async documentation. While the documentation is
mostly fine as-is, it has grown from its original state but remains
without internal structure. Add it now.

Also remove an extra newline.

Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Tested-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com> # Renesas RZ/G2L SMARC
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>
This commit is contained in:
Sakari Ailus 2023-06-20 14:03:02 +02:00 committed by Mauro Carvalho Chehab
parent ec29509467
commit 5202fb581e
1 changed files with 18 additions and 1 deletions
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19
Documentation/driver-api/media/v4l2-subdev.rst
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@ -157,6 +157,9 @@ below.
Using one or the other registration method only affects the probing process, the
run-time bridge-subdevice interaction is in both cases the same.
Registering synchronous sub-devices
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
In the **synchronous** case a device (bridge) driver needs to register the
:c:type:`v4l2_subdev` with the v4l2_device:
@ -175,10 +178,12 @@ You can unregister a sub-device using:
:c:func:`v4l2_device_unregister_subdev <v4l2_device_unregister_subdev>`
(:c:type:`sd <v4l2_subdev>`).
Afterwards the subdev module can be unloaded and
:c:type:`sd <v4l2_subdev>`->dev == ``NULL``.
Registering asynchronous sub-devices
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
In the **asynchronous** case subdevice probing can be invoked independently of
the bridge driver availability. The subdevice driver then has to verify whether
all the requirements for a successful probing are satisfied. This can include a
@ -190,6 +195,9 @@ 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.
Asynchronous sub-device notifiers
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Bridge drivers in turn have to register a notifier object. This is
performed using the :c:func:`v4l2_async_nf_register` call. To
unregister the notifier the driver has to call
@ -208,12 +216,18 @@ the needs of the driver.
:c:func:`v4l2_async_nf_add_i2c` are for bridge and ISP drivers for
registering their async sub-devices with the notifier.
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 firmware. The notifier for the sub-device is unregistered with the
async sub-device.
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:
@ -237,6 +251,9 @@ These functions allocate an async sub-device descriptor which is of type struct
if (IS_ERR(my_asd))
return PTR_ERR(my_asd);
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