diff options
Diffstat (limited to 'Documentation/driver-api/media/v4l2-subdev.rst')
| -rw-r--r-- | Documentation/driver-api/media/v4l2-subdev.rst | 63 |
1 files changed, 45 insertions, 18 deletions
diff --git a/Documentation/driver-api/media/v4l2-subdev.rst b/Documentation/driver-api/media/v4l2-subdev.rst index bb5b1a7cdfd9..8b53da2f9c74 100644 --- a/Documentation/driver-api/media/v4l2-subdev.rst +++ b/Documentation/driver-api/media/v4l2-subdev.rst @@ -122,15 +122,12 @@ Don't forget to cleanup the media entity before the sub-device is destroyed: media_entity_cleanup(&sd->entity); -If the subdev driver intends to process video and integrate with the media -framework, it must implement format related functionality using -:c:type:`v4l2_subdev_pad_ops` instead of :c:type:`v4l2_subdev_video_ops`. - -In that case, the subdev driver may set the link_validate field to provide -its own link validation function. The link validation function is called for -every link in the pipeline where both of the ends of the links are V4L2 -sub-devices. The driver is still responsible for validating the correctness -of the format configuration between sub-devices and video nodes. +If a sub-device driver implements sink pads, the subdev driver may set the +link_validate field in :c:type:`v4l2_subdev_pad_ops` to provide its own link +validation function. For every link in the pipeline, the link_validate pad +operation of the sink end of the link is called. In both cases the driver is +still responsible for validating the correctness of the format configuration +between sub-devices and video nodes. If link_validate op is not set, the default function :c:func:`v4l2_subdev_link_validate_default` is used instead. This function @@ -200,15 +197,45 @@ unregister the notifier the driver has to call 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`. +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. Several functions are available +to add subdevice descriptors to a notifier, depending on the type of device and +the needs of the driver. + +:c:func:`v4l2_async_notifier_add_fwnode_remote_subdev` and +:c:func:`v4l2_async_notifier_add_i2c_subdev` are for bridge and ISP drivers for +registering their async sub-devices with the notifier. + +:c:func:`v4l2_async_register_subdev_sensor_common` 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. + +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: + +.. code-block:: c + + struct my_async_subdev { + struct v4l2_async_subdev asd; + ... + }; + + struct my_async_subdev *my_asd; + struct fwnode_handle *ep; + + ... + + my_asd = v4l2_async_notifier_add_fwnode_remote_subdev(¬ifier, ep, + struct my_async_subdev); + fwnode_handle_put(ep); + + if (IS_ERR(asd)) + return PTR_ERR(asd); The V4L2 core will then use these descriptors to match asynchronously registered subdevices to them. If a match is detected the ``.bound()`` |