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media: v4l2-subdev.rst: Update doc regarding subdev descriptors 

Update the doc to describe the new method of adding subdevice
descriptors to async notifiers.

Signed-off-by: Steve Longerbeam <slongerbeam@gmail.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
hifive-unleashed-5.1
Steve Longerbeam 2018-09-29 15:54:20 -04:00 committed by Mauro Carvalho Chehab
parent 66beb323e4
commit c4a570179c
1 changed files with 19 additions and 11 deletions
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30
Documentation/media/kapi/v4l2-subdev.rst
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@ -247,20 +247,28 @@ 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.
Bridge drivers in turn have to register a notifier object with an array of
subdevice descriptors that the bridge device needs for its operation. This is
Bridge drivers in turn have to register a notifier object. This is
performed using the :c:func:`v4l2_async_notifier_register` call. To
unregister the notifier the driver has to call
:c:func:`v4l2_async_notifier_unregister`. The former of the two functions
takes two arguments: a pointer to struct :c:type:`v4l2_device` and a pointer to
struct :c:type:`v4l2_async_notifier`. The latter contains a pointer to an array
of pointers to subdevice descriptors of type struct :c:type:`v4l2_async_subdev`
type. 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.
takes two arguments: a pointer to struct :c:type:`v4l2_device` and a
pointer to struct :c:type:`v4l2_async_notifier`.
Before registering the notifier, bridge drivers must do two things:
first, the notifier must be initialized using the
:c:func:`v4l2_async_notifier_init`. Second, bridge drivers can then
begin to form a list of subdevice descriptors that the bridge device
needs for its operation. Subdevice descriptors are added to the notifier
using the :c:func:`v4l2_async_notifier_add_subdev` call. This function
takes two arguments: a pointer to struct :c:type:`v4l2_async_notifier`,
and a pointer to the subdevice descripter, which is of type struct
:c:type:`v4l2_async_subdev`.
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.
V4L2 sub-device userspace API
-----------------------------