.. SPDX-License-Identifier: GPL-2.0 The Virtual Media Controller Driver (vimc) ========================================== The vimc driver emulates complex video hardware using the V4L2 API and the Media API. It has a capture device and three subdevices: sensor, debayer and scaler. Topology -------- The topology is hardcoded, although you could modify it in vimc-core and recompile the driver to achieve your own topology. This is the default topology: .. _vimc_topology_graph: .. kernel-figure:: vimc.dot :alt: Diagram of the default media pipeline topology :align: center Media pipeline graph on vimc Configuring the topology ~~~~~~~~~~~~~~~~~~~~~~~~ Each subdevice will come with its default configuration (pixelformat, height, width, ...). One needs to configure the topology in order to match the configuration on each linked subdevice to stream frames through the pipeline. If the configuration doesn't match, the stream will fail. The ``v4l-utils`` package is a bundle of user-space applications, that comes with ``media-ctl`` and ``v4l2-ctl`` that can be used to configure the vimc configuration. This sequence of commands fits for the default topology: .. code-block:: bash media-ctl -d platform:vimc -V '"Sensor A":0[fmt:SBGGR8_1X8/640x480]' media-ctl -d platform:vimc -V '"Debayer A":0[fmt:SBGGR8_1X8/640x480]' media-ctl -d platform:vimc -V '"Scaler":0[fmt:RGB888_1X24/640x480]' media-ctl -d platform:vimc -V '"Scaler":0[crop:(100,50)/400x150]' media-ctl -d platform:vimc -V '"Scaler":1[fmt:RGB888_1X24/300x700]' v4l2-ctl -z platform:vimc -d "RGB/YUV Capture" -v width=300,height=700 v4l2-ctl -z platform:vimc -d "Raw Capture 0" -v pixelformat=BA81 Subdevices ---------- Subdevices define the behavior of an entity in the topology. Depending on the subdevice, the entity can have multiple pads of type source or sink. vimc-sensor: Generates images in several formats using video test pattern generator. Exposes: * 1 Pad source vimc-lens: Ancillary lens for a sensor. Supports auto focus control. Linked to a vimc-sensor using an ancillary link. The lens supports FOCUS_ABSOLUTE control. .. code-block:: bash media-ctl -p ... - entity 28: Lens A (0 pad, 0 link) type V4L2 subdev subtype Lens flags 0 device node name /dev/v4l-subdev6 - entity 29: Lens B (0 pad, 0 link) type V4L2 subdev subtype Lens flags 0 device node name /dev/v4l-subdev7 v4l2-ctl -d /dev/v4l-subdev7 -C focus_absolute focus_absolute: 0 vimc-debayer: Transforms images in bayer format into a non-bayer format. Exposes: * 1 Pad sink * 1 Pad source vimc-scaler: Re-size the image to meet the source pad resolution. E.g.: if the sync pad is configured to 360x480 and the source to 1280x720, the image will be stretched to fit the source resolution. Works for any resolution within the vimc limitations (even shrinking the image if necessary). Exposes: * 1 Pad sink * 1 Pad source vimc-capture: Exposes node /dev/videoX to allow userspace to capture the stream. Exposes: * 1 Pad sink * 1 Pad source Module options -------------- Vimc has a module parameter to configure the driver. * ``allocator=`` memory allocator selection, default is 0. It specifies the way buffers will be allocated. - 0: vmalloc - 1: dma-contig