zephyr/dts/bindings/video/video-interfaces.yaml

# Copyright 2024 NXP
# SPDX-License-Identifier: Apache-2.0

# Common properties for video interface endpoints.

description: |
  A video pipeline usually consists of several devices, e.g. camera sensors, video
  data receivers, video data processors, etc. Data interfaces on these devices are
  described by their child 'port' nodes. Configuration of a port depends on other
  devices in the pipeline and is described by 'endpoint' subnodes.

  If a port can be configured to work with more than one remote device on the same
  bus, an 'endpoint' child node must be provided for each of them. If more than one
  port is present in a device node or there is more than one endpoint at a port, or
  port node needs to be associated with a selected hardware interface, a common
  scheme using '#address-cells', '#size-cells' and 'reg' properties is used.

  All 'port' nodes can be grouped under an optional 'ports' node, which allows to
  specify #address-cells, #size-cells properties independently for the 'port' and
  'endpoint' nodes. For example:

    video_device {
      ...
      ports {
          #address-cells = <1>;
          #size-cells = <0>;

          port@0 {
              ...
              endpoint@0 { ... };
              endpoint@1 { ... };
          };
          port@1 { ... };
      };
    };

  Two 'endpoint' nodes must be linked with each other via their 'remote-endpoint'
  phandles. However, Zephyr does not allow circular dependency, so direct phandle
  references are currently not possible. A 'remote-endpoint-label' string is used
  instead to be able to specify, at least, the label of the peer remote-endpoint.
  For example:

          source: endpoint {
              compatible = "zephyr,video-interfaces";
              remote-endpoint-label = "sink";
          };

          sink: endpoint{
              compatible = "zephyr,video-interfaces";
              remote-endpoint-label = "source";
          };

  This binding contains the most common properties needed to configure an endpoint
  subnode for data exchange with other device. In most cases, properties at the
  peer 'endpoint' node will be identical, however they might be different when
  there is any signal modifications on the bus between two devices, e.g. there are
  logic signal inverters on the lines.  

properties:
  remote-endpoint-label:
    required: true
    type: string
    description: |
      Label of the 'remote-endpoint' subnode that interfaces with this endpoint.
      This property is used as a 'work-around' to be able to declare the remote
      endpoint and should be replaced by a "remote-endpoint" phandle property when
      Zephyr devicetree supports circular dependency in the future.      

  bus-type:
    type: int
    enum:
      - 1 # MIPI CSI-2 C-PHY
      - 2 # MIPI CSI1
      - 3 # CCP2
      - 4 # MIPI CSI-2 D-PHY
      - 5 # Parallel
      - 6 # BT.656
    description: |
      Data bus type.      

  data-shift:
    type: int
    description: |
      On parallel data busses, if bus-width is used to specify the number of
      data lines, data-shift can be used to specify which data lines are used,
      e.g. "bus-width=<8>; data-shift=<2>;" means, that lines 9:2 are used.      

  hsync-active:
    type: int
    enum:
      - 0 # low
      - 1 # high
    description: |
      Active state of the HSYNC signal      

  vsync-active:
    type: int
    enum:
      - 0 # low
      - 1 # high
    description: |
      Active state of the VSYNC signal.      

  pclk-sample:
    type: int
    enum:
      - 0 # falling
      - 1 # rising
      - 2 # both
    description: |
      Sample data on falling, rising or both edges of the pixel clock signal.      

  link-frequencies:
    type: array
    description: |
      Allowed data bus frequencies. For MIPI CSI-2, for instance, this is the
      actual frequency of the bus, not bits per clock per lane value.      

# For serial bus only
  clock-lane:
    type: int
    description: |
      Physical clock lane index. Position of an entry determines the logical
      lane number, while the value of an entry indicates physical lane, e.g. for
      a MIPI CSI-2 bus we could have "clock-lane = <0>;", which places the
      clock lane on hardware lane 0. This property is valid for serial busses
      only (e.g. MIPI CSI-2).      

  data-lanes:
    type: array
    description: |
      An array of physical data lane indexes. Position of an entry determines
      the logical lane number, while the value of an entry indicates physical
      lane, e.g. for 2-lane MIPI CSI-2 bus we could have "data-lanes = <1 2>;",
      assuming the clock lane is on hardware lane 0. If the hardware does not
      support lane reordering, monotonically incremented values shall be used
      from 0 or 1 onwards, depending on whether or not there is also a clock
      lane. This property is valid for serial busses only (e.g. MIPI CSI-2).      

# For parallel bus only
  bus-width:
    type: int
    description: |
      Number of data lines actively used, only valid for parallel busses.