cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
Log | Files | Refs | README | LICENSE | sfeed.txt

vimc.rst (2854B)


      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