Lines Matching +full:sink +full:- +full:only
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
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
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
48 Applications can control all sub-devices through a single interface.
57 Applications can access those hidden controls through the sub-device
60 exception that they deal only with controls implemented in the
61 sub-device.
70 V4L2 sub-devices can notify applications of events as described in
72 nodes, with the exception that it only deals with events generated by
73 the sub-device. Depending on the driver, those events might also be
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 ------------------
151 formats enumeration only. A format negotiation mechanism is required.
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
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
191 - Formats should be propagated from sink pads to source pads. Modifying
192 a format on a source pad should not modify the format on any sink
195 - Sub-devices that scale frames using variable scaling factors should
196 reset the scale factors to default values when sink pads formats are
198 source pads formats should be reset to the sink pads formats.
201 propagating them from one sub-device file handle to another.
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*
309 host frontend and scaler sink and source pads have the default
310 values, as well as the compose rectangle on the scaler's sink pad.
312 2. The application configures the frontend sink pad format's size to
316 3. The application configures the scaler sink pad format's size to
319 on the sink pad is set to V4L2_MBUS_FMT_SGRBG_1X8. The driver
321 scaler's sink pad, and the format to the scaler source pad.
324 rectangle of the scaler's sink pad 1280x960. The driver propagates
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`.
356 On sink pads, cropping is applied relative to the current pad format.
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.
368 rectangle on the subdev's sink pad is scaled to the size configured
375 On source pads, cropping is similar to sink pads, with the exception
377 COMPOSE rectangle on the sink pad. In both sink and source pads, the
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 ---------------------------------------------
415 the sink pad towards the source pad. This is also reflected in the order
424 previous step. The exception to this rule is the sink compose
425 rectangle, which refers to the sink compose bounds rectangle --- if it
428 1. Sink pad format. The user configures the sink pad format. This format
432 2. Sink pad actual crop selection. The sink pad crop defines the crop
433 performed to the sink pad format.
435 3. Sink pad actual compose selection. The size of the sink pad compose
436 rectangle defines the scaling ratio compared to the size of the sink
438 the location of the actual sink compose rectangle in the sink compose
442 performed to the image in the sink compose bounds rectangle.
452 rectangle. For example, if sink crop is not supported, the compose
453 selection will refer to the sink pad format dimensions instead.
456 .. _subdev-image-processing-crop:
458 .. kernel-figure:: subdev-image-processing-crop.svg
459 :alt: subdev-image-processing-crop.svg
464 In the above example, the subdev supports cropping on its sink pad. To
465 configure it, the user sets the media bus format on the subdev's sink
466 pad. Now the actual crop rectangle can be set on the sink pad --- the
468 rectangle to be cropped from the sink format. The size of the sink crop
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
484 ignored in sink compose target. Both of the locations of the source crop
485 rectangles refer to the sink scaling rectangle, independently cropping
489 .. _subdev-image-processing-full:
491 .. kernel-figure:: subdev-image-processing-full.svg
492 :alt: subdev-image-processing-full.svg
497 The subdev driver supports two sink pads and two source pads. The images
498 from both of the sink pads are individually cropped, then scaled and
507 subdev-formats
510 ----------------------------------------------------
512 Simple V4L2 sub-devices do not support multiple, unrelated video streams,
513 and only a single stream can pass through a media link and a media pad.
519 Some hardware, e.g. MIPI CSI-2, support multiplexed streams, that is, multiple
521 link connecting a transmitter source pad with a sink pad on the receiver. For
525 sink pad. The stream-aware receiver will de-multiplex the streams received on
526 the its sink pad and allows to route them individually to one of its source
530 non-multiplexed subdev drivers, but, of course, require a routing configuration
531 where the link between those two types of drivers contains only a single
538 the media pipeline from a source (e.g. a sensor) towards the final sink (e.g. a
540 streams from one end of the link to the other, and sub-devices have routing
541 tables which describe how the incoming streams from sink pads are routed to the
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
565 other. Any number of routes from streams on sink pads towards streams on
567 stream on a source pad, however, only a single route is allowed.
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
594 associated with either sink or source pads of routes configured using the
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.