Lines Matching +full:sub +full:- +full:nodes
1 V4L2 sub-devices
2 ----------------
4 Many drivers need to communicate with sub-devices. These devices can do all
6 encoding or decoding. For webcams common sub-devices are sensors and camera
10 driver with a consistent interface to these sub-devices the
11 :c:type:`v4l2_subdev` struct (v4l2-subdev.h) was created.
13 Each sub-device driver must have a :c:type:`v4l2_subdev` struct. This struct
14 can be stand-alone for simple sub-devices or it might be embedded in a larger
16 low-level device struct (e.g. ``i2c_client``) that contains the device data as
19 it easy to go from a :c:type:`v4l2_subdev` to the actual low-level bus-specific
22 You also need a way to go from the low-level struct to :c:type:`v4l2_subdev`.
27 Bridges might also need to store per-subdev private data, such as a pointer to
28 bridge-specific per-subdev private data. The :c:type:`v4l2_subdev` structure
32 From the bridge driver perspective, you load the sub-device module and somehow
35 Helper functions exists for sub-devices on an I2C bus that do most of this
38 Each :c:type:`v4l2_subdev` contains function pointers that sub-device drivers
39 can implement (or leave ``NULL`` if it is not applicable). Since sub-devices can
44 The top-level ops struct contains pointers to the category ops structs, which
49 .. code-block:: c
82 depending on the sub-device. E.g. a video device is unlikely to support the
88 A sub-device driver initializes the :c:type:`v4l2_subdev` struct using:
94 Afterwards you need to initialize :c:type:`sd <v4l2_subdev>`->name with a
103 .. code-block:: c
105 struct media_pad *pads = &my_sd->pads;
108 err = media_entity_pads_init(&sd->entity, npads, pads);
117 Don't forget to cleanup the media entity before the sub-device is destroyed:
119 .. code-block:: c
121 media_entity_cleanup(&sd->entity);
130 sub-devices. The driver is still responsible for validating the correctness
131 of the format configuration between sub-devices and video nodes.
152 in DT as I2C device nodes. The API used in this second case is described further
156 run-time bridge-subdevice interaction is in both cases the same.
165 After this function was called successfully the subdev->dev field points to
168 If the v4l2_device parent device has a non-NULL mdev field, the sub-device
171 You can unregister a sub-device using:
178 :c:type:`sd <v4l2_subdev>`->dev == ``NULL``.
182 .. code-block:: c
184 err = sd->ops->core->g_std(sd, &norm);
188 .. code-block:: c
192 The macro will to the right ``NULL`` pointer checks and returns ``-ENODEV``
193 if :c:type:`sd <v4l2_subdev>` is ``NULL``, ``-ENOIOCTLCMD`` if either
194 :c:type:`sd <v4l2_subdev>`->core or :c:type:`sd <v4l2_subdev>`->core->g_std is ``NULL``, or the act…
195 :c:type:`sd <v4l2_subdev>`->ops->core->g_std ops.
197 It is also possible to call all or a subset of the sub-devices:
199 .. code-block:: c
206 .. code-block:: c
210 Any error except ``-ENOIOCTLCMD`` will exit the loop with that error. If no
211 errors (except ``-ENOIOCTLCMD``) occurred, then 0 is returned.
214 called. If non-zero, then only those whose group ID match that value will
216 :c:type:`sd <v4l2_subdev>`->grp_id to whatever value it wants (it's 0 by
217 default). This value is owned by the bridge driver and the sub-device driver
228 If the sub-device needs to notify its v4l2_device parent of an event, then
230 whether there is a ``notify()`` callback defined and returns ``-ENODEV`` if not.
243 the driver might decide to return ``-EPROBE_DEFER`` to request further reprobing
265 V4L2 sub-device userspace API
266 -----------------------------
269 V4L2 sub-devices can also be controlled directly by userspace applications.
271 Device nodes named ``v4l-subdev``\ *X* can be created in ``/dev`` to access
272 sub-devices directly. If a sub-device supports direct userspace configuration
275 After registering sub-devices, the :c:type:`v4l2_device` driver can create
276 device nodes for all registered sub-devices marked with
278 :c:func:`v4l2_device_register_subdev_nodes`. Those device nodes will be
279 automatically removed when sub-devices are unregistered.
293 controls implemented in the sub-device. Depending on the driver, those
295 nodes.
303 events generated by the sub-device. Depending on the driver, those
304 events can also be reported by one (or several) V4L2 device nodes.
306 Sub-device drivers that want to use events need to set the
309 the sub-device. After registration events can be queued as usual on the
317 All ioctls not in the above list are passed directly to the sub-device
321 I2C sub-device drivers
322 ----------------------
325 ease the use of these drivers (``v4l2-common.h``).
335 .. code-block:: c
344 .. code-block:: c
346 v4l2_i2c_subdev_init(&state->sd, client, subdev_ops);
354 .. code-block:: c
364 .. code-block:: c
370 .. code-block:: c
376 when the ``remove()`` callback is called. This will unregister the sub-device
377 from the bridge driver. It is safe to call this even if the sub-device was
390 .. code-block:: c
402 are only used if the previous argument is 0. A non-zero argument means that you
429 V4L2 sub-device functions and data structures
430 ---------------------------------------------
432 .. kernel-doc:: include/media/v4l2-subdev.h
434 .. kernel-doc:: include/media/v4l2-async.h