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Diffstat (limited to 'Documentation/media/kapi/v4l2-subdev.rst')
| -rw-r--r-- | Documentation/media/kapi/v4l2-subdev.rst | 30 |
1 files changed, 19 insertions, 11 deletions
diff --git a/Documentation/media/kapi/v4l2-subdev.rst b/Documentation/media/kapi/v4l2-subdev.rst index e1f0b726e438..1280e05b662b 100644 --- a/Documentation/media/kapi/v4l2-subdev.rst +++ b/Documentation/media/kapi/v4l2-subdev.rst @@ -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 ----------------------------- |