1.. SPDX-License-Identifier: GPL-2.0 2 3The Virtual Media Controller Driver (vimc) 4========================================== 5 6The vimc driver emulates complex video hardware using the V4L2 API and the Media 7API. It has a capture device and three subdevices: sensor, debayer and scaler. 8 9Topology 10-------- 11 12The topology is hardcoded, although you could modify it in vimc-core and 13recompile the driver to achieve your own topology. This is the default topology: 14 15.. _vimc_topology_graph: 16 17.. kernel-figure:: vimc.dot 18 :alt: Diagram of the default media pipeline topology 19 :align: center 20 21 Media pipeline graph on vimc 22 23Configuring the topology 24~~~~~~~~~~~~~~~~~~~~~~~~ 25 26Each subdevice will come with its default configuration (pixelformat, height, 27width, ...). One needs to configure the topology in order to match the 28configuration on each linked subdevice to stream frames through the pipeline. 29If the configuration doesn't match, the stream will fail. The ``v4l-utils`` 30package is a bundle of user-space applications, that comes with ``media-ctl`` and 31``v4l2-ctl`` that can be used to configure the vimc configuration. This sequence 32of commands fits for the default topology: 33 34.. code-block:: bash 35 36 media-ctl -d platform:vimc -V '"Sensor A":0[fmt:SBGGR8_1X8/640x480]' 37 media-ctl -d platform:vimc -V '"Debayer A":0[fmt:SBGGR8_1X8/640x480]' 38 media-ctl -d platform:vimc -V '"Sensor B":0[fmt:SBGGR8_1X8/640x480]' 39 media-ctl -d platform:vimc -V '"Debayer B":0[fmt:SBGGR8_1X8/640x480]' 40 v4l2-ctl -z platform:vimc -d "RGB/YUV Capture" -v width=1920,height=1440 41 v4l2-ctl -z platform:vimc -d "Raw Capture 0" -v pixelformat=BA81 42 v4l2-ctl -z platform:vimc -d "Raw Capture 1" -v pixelformat=BA81 43 44Subdevices 45---------- 46 47Subdevices define the behavior of an entity in the topology. Depending on the 48subdevice, the entity can have multiple pads of type source or sink. 49 50vimc-sensor: 51 Generates images in several formats using video test pattern generator. 52 Exposes: 53 54 * 1 Pad source 55 56vimc-debayer: 57 Transforms images in bayer format into a non-bayer format. 58 Exposes: 59 60 * 1 Pad sink 61 * 1 Pad source 62 63vimc-scaler: 64 Re-size the image to meet the source pad resolution. E.g.: if the sync 65 pad is configured to 360x480 and the source to 1280x720, the image will 66 be stretched to fit the source resolution. Works for any resolution 67 within the vimc limitations (even shrinking the image if necessary). 68 Exposes: 69 70 * 1 Pad sink 71 * 1 Pad source 72 73vimc-capture: 74 Exposes node /dev/videoX to allow userspace to capture the stream. 75 Exposes: 76 77 * 1 Pad sink 78 * 1 Pad source 79 80Module options 81-------------- 82 83Vimc has a module parameter to configure the driver. 84 85* ``allocator=<unsigned int>`` 86 87 memory allocator selection, default is 0. It specifies the way buffers 88 will be allocated. 89 90 - 0: vmalloc 91 - 1: dma-contig 92