openbmc/phosphor-buttons/README.md

# phosphor-buttons

Phosphor-buttons has a collection of IO event handler interfaces for physical
inputs which are typically part of some sort of panel.

It defines an individual dbus interface object for each physical button/switch
inputs such as power button, reset button etc. Each button interface monitors
its associated IO for event changes and emits signals that the button-handler
application listens for.

## Button Behavior

### Power Button

All events occur when the button is released.

If the power is off, power on the host.

If the power is on, it depends on how long the press was and which options are
enabled:

- Short press: Do a host power off
- Long press, as determined by the 'long-press-time-ms' meson option: Do a
  chassis (hard) power off.

#### Custom Power Button Profiles

The 'power-button-profile' meson option can be used to select custom power
button profiles that have different behaviors.

Available profiles are:

- host_then_chassis_poweroff: When power is on, short presses are ignored and a
  long press issues a host power off first and then a chassis power off if held
  past a certain time. [This class](inc/host_then_chassis_poweroff.hpp) has
  additional details.

### Multi-Host Buttons

See [this section below](#group-gpio-config).

### Reset Button

When released:

- If 'reset-button-do-warm-reboot' meson option is set to enabled, does warm
  reboot the host.
- Otherwise, reboots the host (default behavior)

### ID Button

When released, toggles the 'enclosure_identify' LED group provided by the
phosphor-led-manager repository. The group name can be changed using the
'id-led-group' meson option.

## Gpio defs config

In order to monitor a button/input interface the respective gpio config details
should be mentioned in the gpio defs json file -
`/etc/default/obmc/gpio/gpio_defs.json`

1. The button interface type name.
2. An array consists of single or multiple gpio configs associated with the
   specific button interface.

A gpio can be mapped using the "pin" or "num" keyword. The "pin" key uses
alphanumerical references while the "num" key supports the integer pin number.

## example gpio def Json config

```json
{
    "gpio_definitions": [
        {
            "name": "POWER_BUTTON",
            "gpio_config" :[
               {
                "pin": "D0",
                "direction": "both"
               }
            ]
        },
        {
            "name": "RESET_BUTTON",
            "gpio_config" :[
                {
                "pin": "AB0",
                "direction": "both"
                 }
            ]
        },
        {
            "name" : "HOST_SELECTOR",

            "group_gpio_config" : [
            {
                "pin": "AA4",
                "direction": "both"
            },
            {
                "pin": "AA5",
                "direction": "both"
            },
            {
                "pin": "AA6",
                "direction": "both"
            },
            {
                "pin": "AA7",
                "direction": "both"
            }
            ]
        },

}
```

## Single gpio config

This config is original config which can be used for configs with only single
gpio such as power button,reset button, OCP debug card host select button.

```json
{
    "name": "POWER_BUTTON",
    "pin": "D0",
    "direction": "both"
},
```

**Note:** this config is used by most of the other platforms so this format is
kept as it is so that existing gpio configs do not get affected.

## Group gpio config

The following configs are related to multi-host bmc systems more info explained
in the design:
<https://github.com/openbmc/docs/blob/master/designs/multihost-phosphor-buttons.md>

### Host selector gpio config example

The host selector has four gpios associated. So the related gpios are mentioned
in a json array named group_gpio_config.

- name - This is name of the specific gpio line
- pin - This represents the pin number from linux dts file.
- polarity - polarity type of the gpio
- max_position - This represents the max number of hosts in the multi-host bmc
  system.
- host_selector_map - This map is oem specific host position map which has how
  the value read from the host selector gpios is mapped to the respective host
  number.

Example : The value of "7" derived from the 4 host select gpio lines are mapped
to host position 1.

```json
{
  "name": "HOST_SELECTOR",

  "group_gpio_config": [
    {
      "name": "host_select_0",
      "pin": "AA4",
      "direction": "both",
      "polarity": "active_high"
    },
    {
      "name": "host_select_1",
      "pin": "AA5",
      "direction": "both",
      "polarity": "active_high"
    },
    {
      "name": "host_select_2",
      "pin": "AA6",
      "direction": "both",
      "polarity": "active_high"
    },
    {
      "name": "host_select_3",
      "pin": "AA7",
      "direction": "both",
      "polarity": "active_high"
    }
  ],
  "max_position": 4,
  "host_selector_map": {
    "6": 0,
    "7": 1,
    "8": 2,
    "9": 3,
    "10": 4,
    "11": 0,
    "12": 1,
    "13": 2,
    "14": 3,
    "15": 4
  }
}
```

### Host selector cpld config example

There are also some systems that get the host selector selection from the CPLD,
the configuration is provided below.

- name - The button interface type name.
- i2c_bus - The i2c bus of cpld
- i2c_address - The i2c address of cpld
- register_name - The register file name exported by CLD driver for IO event
  listen
- max_position - This represents the max number of hosts in the multi-host bmc
  system.

```json
{
  "cpld_definitions": [
    {
      "name": "HOST_SELECTOR",
      "i2c_bus": 12,
      "i2c_address": 15,
      "register_name": "uart-selection-debug-card",
      "max_position": 4
    }
  ]
}
```

### Serial uart mux config

Similar to host selector there are multiple gpios associated with the serial
uart mux. These gpio configs are specificed as part of json array
"group_gpio_config".

Here the serial uart mux output is accessed via OCP debug card. SO the OCP debug
card present gpio is mentioned part of the group_gpio_config. The debug card
present gpio is identified by its name "debug_card_present".

The other gpios part of the group gpio config is serial uart MUX gpio select
lines and serial_uart_rx line.

- name - this is name of the specific gpio line
- pin - this represents the pin number from linux dts file.
- polarity - polarity type of the gpio
- serial_uart_mux_map - This is the map for selected host position to the serial
  uart mux select output value

```json
{
  "name": "SERIAL_UART_MUX",

  "group_gpio_config": [
    {
      "name": "serial_uart_sel_0",
      "pin": "E0",
      "direction": "out",
      "polarity": "active_high"
    },
    {
      "name": "serial_uart_sel_1",
      "pin": "E1",
      "direction": "out",
      "polarity": "active_high"
    },
    {
      "name": "serial_uart_sel_2",
      "pin": "E2",
      "direction": "out",
      "polarity": "active_high"
    },
    {
      "name": "serial_uart_sel_3",
      "pin": "E3",
      "direction": "out",
      "polarity": "active_high"
    },
    {
      "name": "serial_uart_rx",
      "pin": "E4",
      "direction": "out",
      "polarity": "active_high"
    },
    {
      "name": "debug_card_present",
      "pin": "R3",
      "direction": "both",
      "polarity": "active_high"
    }
  ],
  "serial_uart_mux_map": {
    "0": 4,
    "1": 0,
    "2": 1,
    "3": 2,
    "4": 3
  }
}
```