110 lines
3.4 KiB
ReStructuredText
110 lines
3.4 KiB
ReStructuredText
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.. SPDX-License-Identifier: GPL-2.0
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The Virtual Media Controller Driver (vimc)
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==========================================
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The vimc driver emulates complex video hardware using the V4L2 API and the Media
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API. It has a capture device and three subdevices: sensor, debayer and scaler.
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Topology
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--------
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The topology is hardcoded, although you could modify it in vimc-core and
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recompile the driver to achieve your own topology. This is the default topology:
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.. _vimc_topology_graph:
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.. kernel-figure:: vimc.dot
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:alt: Diagram of the default media pipeline topology
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:align: center
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Media pipeline graph on vimc
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Configuring the topology
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~~~~~~~~~~~~~~~~~~~~~~~~
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Each subdevice will come with its default configuration (pixelformat, height,
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width, ...). One needs to configure the topology in order to match the
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configuration on each linked subdevice to stream frames through the pipeline.
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If the configuration doesn't match, the stream will fail. The ``v4l-utils``
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package is a bundle of user-space applications, that comes with ``media-ctl`` and
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``v4l2-ctl`` that can be used to configure the vimc configuration. This sequence
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of commands fits for the default topology:
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.. code-block:: bash
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media-ctl -d platform:vimc -V '"Sensor A":0[fmt:SBGGR8_1X8/640x480]'
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media-ctl -d platform:vimc -V '"Debayer A":0[fmt:SBGGR8_1X8/640x480]'
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media-ctl -d platform:vimc -V '"Sensor B":0[fmt:SBGGR8_1X8/640x480]'
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media-ctl -d platform:vimc -V '"Debayer B":0[fmt:SBGGR8_1X8/640x480]'
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v4l2-ctl -z platform:vimc -d "RGB/YUV Capture" -v width=1920,height=1440
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v4l2-ctl -z platform:vimc -d "Raw Capture 0" -v pixelformat=BA81
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v4l2-ctl -z platform:vimc -d "Raw Capture 1" -v pixelformat=BA81
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Subdevices
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----------
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Subdevices define the behavior of an entity in the topology. Depending on the
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subdevice, the entity can have multiple pads of type source or sink.
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vimc-sensor:
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Generates images in several formats using video test pattern generator.
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Exposes:
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* 1 Pad source
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vimc-debayer:
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Transforms images in bayer format into a non-bayer format.
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Exposes:
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* 1 Pad sink
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* 1 Pad source
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vimc-scaler:
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Scale up the image by a factor of 3. E.g.: a 640x480 image becomes a
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1920x1440 image. (this value can be configured, see at
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`Module options`_).
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Exposes:
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* 1 Pad sink
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* 1 Pad source
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vimc-capture:
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Exposes node /dev/videoX to allow userspace to capture the stream.
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Exposes:
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* 1 Pad sink
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* 1 Pad source
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Module options
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---------------
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Vimc has a few module parameters to configure the driver. You should pass
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those arguments to each subdevice, not to the vimc module. For example::
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vimc_subdevice.param=value
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* ``vimc_scaler.sca_mult=<unsigned int>``
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Image size multiplier factor to be used to multiply both width and
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height, so the image size will be ``sca_mult^2`` bigger than the
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original one. Currently, only supports scaling up (the default value
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is 3).
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* ``vimc_debayer.deb_mean_win_size=<unsigned int>``
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Window size to calculate the mean. Note: the window size needs to be an
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odd number, as the main pixel stays in the center of the window,
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otherwise the next odd number is considered (the default value is 3).
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Source code documentation
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-------------------------
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vimc-streamer
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~~~~~~~~~~~~~
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.. kernel-doc:: drivers/media/platform/vimc/vimc-streamer.h
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:internal:
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.. kernel-doc:: drivers/media/platform/vimc/vimc-streamer.c
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