# rail

## Description

A voltage rail that is enabled or monitored by the power sequencer device.

The "check_status_vout", "compare_voltage_to_limit", and "gpio" properties
specify how to obtain the pgood status of the rail. You can specify more than
one of these properties if necessary.

## Properties

| Name                     |      Required       | Type                    | Description                                                                                                                                                                                                                                                                                                                    |
| :----------------------- | :-----------------: | :---------------------- | :----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| name                     |         yes         | string                  | Unique name for the rail. Can only contain letters (A-Z, a-z), numbers (0-9), period (.), and underscore (\_).                                                                                                                                                                                                                 |
| presence                 |         no          | string                  | D-Bus inventory path of a system component which must be present in order for the rail to be present. If this property is not specified, the rail is assumed to always be present.                                                                                                                                             |
| page                     | see [notes](#notes) | number                  | PMBus PAGE number of the rail.                                                                                                                                                                                                                                                                                                 |
| is_power_supply_rail     |         no          | boolean (true or false) | If true, this rail is produced by a power supply. Power supply rails require special error handling. If an error is detected in a power supply device, and the pgood status is false for a power supply rail, the power supply error is logged as the cause of the pgood failure. The default value of this property is false. |
| check_status_vout        |         no          | boolean (true or false) | If true, determine the pgood status of the rail by checking the value of the PMBus STATUS_VOUT command. If one of the error bits is set, the rail pgood will be considered false. The default value of this property is false.                                                                                                 |
| compare_voltage_to_limit |         no          | boolean (true or false) | If true, determine the pgood status of the rail by comparing the output voltage (READ_VOUT) to the undervoltage fault limit (VOUT_UV_FAULT_LIMIT). If the output voltage is below this limit, the rail pgood will be considered false. The default value of this property is false.                                            |
| gpio                     |         no          | [gpio](gpio.md)         | Determine the pgood status of the rail by reading a GPIO.                                                                                                                                                                                                                                                                      |

### Notes

- The "page" property is required if the "check_status_vout" or
  "compare_voltage_to_limit" property is true.

## Examples

```
{
    "name": "VDD_CPU0",
    "page": 11,
    "check_status_vout": true
}
```

```
{
    "name": "VCS_CPU1",
    "presence": "/xyz/openbmc_project/inventory/system/chassis/motherboard/cpu1",
    "gpio": { "line": 60 }
}
```