# device

## Description
A hardware device within the chassis.

The following devices should be defined in the config file:
* Voltage regulators that require configuration or monitoring.
* Other devices that are required to configure or monitor regulators.  For
  example, an I/O expander may provide necessary information about a regulator.

## Properties
| Name | Required | Type | Description |
| :--- | :------: | :--- | :---------- |
| comments | no | array of strings | One or more comment lines describing this device. |
| id | yes | string | Unique ID for this device.  Can only contain letters (A-Z, a-z), numbers (0-9), and underscore (\_). |
| is_regulator | yes | boolean (true or false) | Indicates whether this device is a voltage regulator (phase controller). |
| fru | yes | string | Field-Replaceable Unit (FRU) for this device.  Specify the D-Bus inventory path of the FRU.  If the device itself is not a FRU, specify the FRU that contains it. |
| i2c_interface | yes | [i2c_interface](i2c_interface.md) | I2C interface to this device. |
| presence_detection | no | [presence_detection](presence_detection.md) | Specifies how to detect whether this device is present.  If this property is not specified, the device is assumed to always be present. |
| configuration | no | [configuration](configuration.md) | Specifies configuration changes that should be applied to this device.  These changes usually override hardware default settings.  The configuration changes are applied during the boot before regulators are enabled. |
| rails | no | array of [rails](rail.md) | One or more voltage rails produced by this device.  This property can only be specified if the "is_regulator" property is true. |

## Example
```
{
  "comments": [ "IR35221 regulator producing the Vdd rail" ],
  "id": "vdd_regulator",
  "is_regulator": true,
  "fru": "/system/chassis/motherboard/regulator2",
  "i2c_interface": {
    "bus": 1,
    "address": "0x70"
  },
  "configuration": {
    "rule_id": "configure_ir35221_rule"
  },
  "rails": [
    {
      "id": "vdd",
      ... details omitted ...
    }
  ]
}
```