Lines Matching +full:sub +full:- +full:device
1 .. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
6 Sub-device Interface
13 components as software blocks called sub-devices.
15 V4L2 sub-devices are usually kernel-only objects. If the V4L2 driver
16 implements the media device API, they will automatically inherit from
17 media entities. Applications will be able to enumerate the sub-devices
21 In addition to make sub-devices discoverable, drivers can also choose to
23 sub-device driver and the V4L2 device driver support this, sub-devices
24 will feature a character device node on which ioctls can be called to
26 - query, read and write sub-devices controls
28 - subscribe and unsubscribe to events and retrieve them
30 - negotiate image formats on individual pads
32 - inspect and modify internal data routing between pads of the same entity
34 Sub-device character device nodes, conventionally named
35 ``/dev/v4l-subdev*``, use major number 81.
37 Drivers may opt to limit the sub-device character devices to only expose
38 operations that do not modify the device state. In such a case the sub-devices
39 are referred to as ``read-only`` in the rest of this documentation, and the
46 Most V4L2 controls are implemented by sub-device hardware. Drivers
47 usually merge all controls and expose them through video device nodes.
48 Applications can control all sub-devices through a single interface.
55 single device, all but one of the identical controls are hidden.
57 Applications can access those hidden controls through the sub-device
59 behave identically as when issued on V4L2 device nodes, with the
61 sub-device.
64 one (or several) V4L2 device nodes.
70 V4L2 sub-devices can notify applications of events as described in
71 :ref:`event`. The API behaves identically as when used on V4L2 device
73 the sub-device. Depending on the driver, those events might also be
74 reported on one (or several) V4L2 device nodes.
77 .. _pad-level-formats:
79 Pad-level Formats
84 Pad-level formats are only applicable to very complex devices that
85 need to expose low-level format configuration to user space. Generic
103 :ref:`pipeline-scaling`, where image scaling can be performed on both
107 .. _pipeline-scaling:
109 .. kernel-figure:: pipeline.dot
125 Drivers that implement the :ref:`media API <media-controller-intro>`
126 can expose pad-level image format configuration to applications. When
130 negotiate formats on a per-pad basis.
138 Pad-level image format configuration support can be tested by calling
140 0. If the driver returns an ``EINVAL`` error code pad-level format
141 configuration is not supported by the sub-device.
145 ------------------
159 configuration. Modifying those 'try' formats leaves the device state
161 and the hardware state stored in the device itself).
163 While not kept as part of the device state, try formats are stored in
164 the sub-device file handles. A
166 the last try format set *on the same sub-device file handle*. Several
167 applications querying the same sub-device at the same time will thus not
170 To find out whether a particular format is supported by the device,
173 verify and, if needed, change the requested ``format`` based on device
179 guaranteed to be supported by the device. In particular, drivers
181 to an :ref:`VIDIOC_SUBDEV_S_FMT <VIDIOC_SUBDEV_G_FMT>` call as-is
185 Drivers automatically propagate formats inside sub-devices. When a try
187 the same sub-device can be modified by the driver. Drivers are free to
188 modify formats as required by the device. However, they should comply
191 - Formats should be propagated from sink pads to source pads. Modifying
195 - Sub-devices that scale frames using variable scaling factors should
201 propagating them from one sub-device file handle to another.
205 different formats matching device requirements as being compatible.
207 :ref:`sample-pipeline-config` shows a sample configuration sequence
208 for the pipeline described in :ref:`pipeline-scaling` (table columns
220 .. _sample-pipeline-config:
222 .. flat-table:: Sample Pipeline Configuration
223 :header-rows: 1
224 :stub-columns: 0
227 * -
228 - Sensor/0
231 - Frontend/0
234 - Frontend/1
237 - Scaler/0
240 - Scaler/0
243 - Scaler/1
246 * - Initial state
247 - 2048x1536
250 - (default)
251 - (default)
252 - (default)
253 - (default)
254 - (default)
255 * - Configure frontend sink format
256 - 2048x1536
259 - *2048x1536*
262 - *2046x1534*
265 - (default)
266 - (default)
267 - (default)
268 * - Configure scaler sink format
269 - 2048x1536
272 - 2048x1536
275 - 2046x1534
278 - *2046x1534*
281 - *0,0/2046x1534*
282 - *2046x1534*
285 * - Configure scaler sink compose selection
286 - 2048x1536
289 - 2048x1536
292 - 2046x1534
295 - 2046x1534
298 - *0,0/1280x960*
299 - *1280x960*
334 be applied as-is by the driver without being modified.
337 .. _v4l2-subdev-selections:
340 ---------------------------------------------
342 Many sub-devices support cropping frames on their input or output pads
354 selection targets :ref:`v4l2-selections-common`.
357 The pad format represents the image size as received by the sub-device
359 represents the sub-image that will be transmitted further inside the
360 sub-device for processing.
384 the image size either up or down. :ref:`v4l2-selection-flags`
388 --------------------------
405 pixel array is not rectangular but cross-shaped or round. The maximum
409 .. _format-propagation:
412 ---------------------------------------------
425 rectangle, which refers to the sink compose bounds rectangle --- if it
456 .. _subdev-image-processing-crop:
458 .. kernel-figure:: subdev-image-processing-crop.svg
459 :alt: subdev-image-processing-crop.svg
466 pad. Now the actual crop rectangle can be set on the sink pad --- the
473 .. _subdev-image-processing-scaling-multi-source:
475 .. kernel-figure:: subdev-image-processing-scaling-multi-source.svg
476 :alt: subdev-image-processing-scaling-multi-source.svg
489 .. _subdev-image-processing-full:
491 .. kernel-figure:: subdev-image-processing-full.svg
492 :alt: subdev-image-processing-full.svg
507 subdev-formats
510 ----------------------------------------------------
512 Simple V4L2 sub-devices do not support multiple, unrelated video streams,
519 Some hardware, e.g. MIPI CSI-2, support multiplexed streams, that is, multiple
525 sink pad. The stream-aware receiver will de-multiplex the streams received on
530 non-multiplexed subdev drivers, but, of course, require a routing configuration
540 streams from one end of the link to the other, and sub-devices have routing
544 A stream ID is a media pad-local identifier for a stream. Streams IDs of
548 of the sub-device.
551 sub-device and a (pad, stream) pair. For sub-devices that do not support
557 The addition of streams to the V4L2 sub-device interface moves the sub-device
561 the same as without streams (see :ref:`format-propagation`).
563 Instead of the sub-device wide merging of streams from all sink pads
576 The configuration of the streams is done individually for each sub-device and
577 the validity of the streams between sub-devices is validated when the pipeline
582 1) Set up links. Connect the pads between sub-devices using the :ref:`Media
586 setting the routing table for the sub-device using
589 sub-device to default values.
592 are configured separately as documented for plain sub-devices in
593 :ref:`format-propagation`. The stream ID is set to the same stream ID
602 - Two identical sensors (Sensor A and Sensor B). Each sensor has a single source
605 - Multiplexer bridge (Bridge). The bridge has two sink pads, connected to the
608 - Receiver in the SoC (Receiver). The receiver has a single sink pad (pad 0),
609 connected to the bridge, and two source pads (pads 1-2), going to the DMA
612 - DMA Engines in the SoC (DMA Engine), one for each stream. Each DMA engine is
615 The sensors, the bridge and the receiver are modeled as V4L2 sub-devices,
616 exposed to userspace via /dev/v4l-subdevX device nodes. The DMA engines are
623 not differ from normal non-multiplexed media controller setup.
627 .. flat-table:: Bridge routing table
628 :header-rows: 1
630 * - Sink Pad/Stream
631 - Source Pad/Stream
632 - Routing Flags
633 - Comments
634 * - 0/0
635 - 2/0
636 - V4L2_SUBDEV_ROUTE_FL_ACTIVE
637 - Pixel data stream from Sensor A
638 * - 1/0
639 - 2/1
640 - V4L2_SUBDEV_ROUTE_FL_ACTIVE
641 - Pixel data stream from Sensor B
643 .. flat-table:: Receiver routing table
644 :header-rows: 1
646 * - Sink Pad/Stream
647 - Source Pad/Stream
648 - Routing Flags
649 - Comments
650 * - 0/0
651 - 1/0
652 - V4L2_SUBDEV_ROUTE_FL_ACTIVE
653 - Pixel data stream from Sensor A
654 * - 0/1
655 - 2/0
656 - V4L2_SUBDEV_ROUTE_FL_ACTIVE
657 - Pixel data stream from Sensor B
669 stream endpoint in each sub-device.