gpio-presence-sensor

This program was originally implemented following the design.

Configuration

See the full design for more details.

Example EM config fragments:

{
  Exposes:
  [
    {
      "Name": "com.meta.Hardware.Yv4.cable0",
      "PresencePinNames": ["presence-cable0"],
      "PresencePinValues": [1],
      "Type": "GPIODeviceDetect"
    },
    {
      "Name": "com.meta.Hardware.Yv4.ComputeCard",
      "PresencePinNames": ["presence-slot0a", "presence-slot0b"],
      "PresencePinValues": [0, 1],
      "Type": "GPIODeviceDetect"
    },
    {
      "Name": "com.meta.Hardware.Yv4.SidecarExpansion",
      "PresencePinNames": ["presence-slot0a", "presence-slot0b"],
      "PresencePinValues": [1, 0],
      "Type": "GPIODeviceDetect"
    },
    {
      "Name": "com.meta.Hardware.Yv4.AirBlocker",
      "PresencePinNames": ["presence-slot0a", "presence-slot0b"],
      "PresencePinValues": [1, 1],
      "Type": "GPIODeviceDetect"
    },
    {
      "Name": "com.meta.Hardware.Yv4.fanboard0",
      "PresencePinNames": ["presence-fanboard0"],
      "PresencePinValues": [0],
      "Type": "GPIODeviceDetect"
    },
    ...
  ],
  ...
  "Name": "My Chassis",
  "Probe": "xyz.openbmc_project.FruDevice({'BOARD_PRODUCT_NAME': 'MYBOARDPRODUCT*'})",
  "Type": "Board",
}

The above configuration can then cause a Probe match in another configuration, like below:

{
  Exposes:
  [
      {
        "Address": "0x28",
        "Bus": 5,
        "EntityId": 7,
        "EntityInstance": 0,
        "Name": "fanboard_air_inlet",
        "Name1": "fanboard_air_outlet",
        "Type": "NCT7802"
    },
    ...
  ],
  ...
  "Name": "My Fan Board 0",
  "Probe": "xyz.openbmc_project.Inventory.Source.DevicePresence({'Name': 'com.meta.Hardware.Yv4.fanboard0'})",
  "Type": "Board",
}

Notice the xyz.openbmc_project.Inventory.Source.DevicePresence interface. This is what the gpio-presence daemon exposes on dbus when the hardware is detected as present. The Name property in the Probe statement is the same as configured as in the first json fragment.

Applications

Applications include detecting fan boards, air blockers, cables and other simple components for which no standard / well-defined way exists to detect them otherwise.

It can also be used as detection redundancy in case another detection mechanism like FRU eeprom is corrupted or unavailable.

References