APM(4) | Device Drivers Manual (loongson) | APM(4)

# NAME

`apm` — advanced power management device interface

# SYNOPSIS

`apm0 at mainbus0`

# DESCRIPTION

The `apm` driver provides generic power and battery control, relying on device specific drivers to provide the actual information.

The `apm` driver provides an interface which simulates the Advanced Power Management (APM) BIOS functions encountered on some x86 hardware. The BIOS functions are translated into the appropriate microcontroller requests by the hardware specific drivers, like ykbec(4). Currently only battery level, AC connection, and charging status are available from the `apm` device. Suspend/resume and other power events are not yet supported.

The `apm` driver implements the following ioctl(2) calls. They are defined in `<machine/apmvar.h>`.

`APM_IOC_GETPOWER`
  (`struct apm_power_info`) Request the current power state. The argument structure is as follows:

      struct apm_power_info {
      	u_char battery_state;
      	u_char ac_state;
      	u_char battery_life;
      	u_char spare1;
      	u_int minutes_left;
      	u_int spare2[6];
      };

  The following values are defined for battery_state:

  `APM_BATT_HIGH`
    Battery has a high state of charge.
  `APM_BATT_LOW`
    Battery has a low state of charge.
  `APM_BATT_CRITICAL`
    Battery has a critical state of charge.
  `APM_BATT_CHARGING`
    Battery is not high, low, or critical and is currently charging.
  `APM_BATT_UNKNOWN`
    Cannot read the current battery state.
  `APM_BATTERY_ABSENT`
    No battery installed.

  The following values are defined for ac_state:

  `APM_AC_OFF`
    External power not detected.
  `APM_AC_ON`
    External power detected.

  The battery_life value contains the estimated percentage of battery life available. 100% indicates a full charge.

  The minutes_left value contains the estimated number of minutes of battery life remaining.

`APM_IOC_PRN_CTL`
  (`int`) This ioctl(2) controls message output by the `apm` driver when a power change event is detected. The integer parameter is one of:
  `APM_PRINT_ON`
    All power change events result in a message. This is the normal operating mode for the driver.
  `APM_PRINT_OFF`
    Power change event messages are suppressed.
  `APM_PRINT_PCT`
    Power change event messages are suppressed unless the estimated battery life percentage changes.

# FILES

/dev/apm
  APM data device. May only be opened read-only. May be opened by multiple concurrent users.
/dev/apmctl
  APM control device. May be opened read-write or write-only. May only be opened by one user at a time. An attempt to open the file when in use will fail, returning `EBUSY`.

# SEE ALSO

intro(4), ykbec(4), apm(8), apmd(8)

# BUGS

Suspend and resume are not supported.

January 30, 2023 | Debian