NAME
apm
—
advanced power management device
interface
SYNOPSIS
apm0 at bios0 flags 0x0000
DESCRIPTION
The apm
driver provides an interface to
the Advanced Power Management (APM) BIOS functions. The driver supports
versions 1.0, 1.1, and 1.2 interface specifications.
This driver also provides an interface to acpi(4) on some machines.
The low two bytes of the flags specify the version of the specification driver should conform to in binary decimal notation. The value of 0x0101 would specify version 1.1 of the interface specification to be used.
The value of 0x10000 specifies whether to leave interrupts enabled when calling APM BIOS routines. This is needed for some IBM laptops, the symptoms are hangs and freezes on suspend, stand by, and hibernation activities.
The value of 0x20000 specifies to swap the bytes of the battery life estimation (the DX register) as given from the APM BIOS. This is needed for some SONY VAIO laptops, such as some 505 models.
Configuration options:
APMDEBUG
- Enable various driver status messages.
DIAGNOSTIC
- Enable debugging messages.
DEBUG
- Enable other debugging messages.
The apm
driver implements the following
ioctl(2) calls. They are defined in
<machine/apmvar.h>
.
APM_IOC_REJECT
- Not implemented. DO NOT USE.
APM_IOC_STANDBY
- (
no parameters
) Request “standby” mode. APM_IOC_SUSPEND
- (
no parameters
) Request “suspend” mode. 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
- Can not 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.
APM_AC_BACKUP
- Backup power in use.
APM_AC_UNKNOWN
- External power state unknown.
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_NEXTEVENT
- (
struct apm_event_info
) The APM driver stores up toAPM_NEVENTS
events. This was defined as 16 at the time this documentation was written. If the event list is full when a new event is detected the new event is lost.APM_IOC_NEXTEVENT
ioctl returns the next event on the list orEAGAIN
if the event list is empty. The format of the returned event is:struct apm_event_info { u_int type; u_int index; u_int spare[8]; };
APM_IOC_DEV_CTL
- (
struct apm_ctl
) Allows an application to directly set the APM operating mode. The argument structure is as follows:struct apm_ctl { u_int dev; u_int mode; };
dev indicates the device, typically
APM_DEV_ALLDEVS
.mode indicates the desired operating mode. Possible values are
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.
However, in no case will power status messages be displayed until the battery life goes below the percentage in the sysctl(8) state variable
machdep.apmwarn
. Settingmachdep.apmwarn
to zero disables all warnings regardless of theAPM_IOC_PRN_CTL
setting.
As noted above, the operation of the APM driver can be modified
using the machdep.apmwarn
sysctl(8) variable. Another driver modifier is the
machdep.apmhalt
variable. When
machdep.apmhalt
is set to 1 the APM power down code
is modified in a way necessary for correct operation on some systems, mainly
IBM laptops. If your system does not power down when given the command
halt -p
try setting
machdep.apmhalt
to 1 using
sysctl(8). The variable can be set at boot time in
sysctl.conf(5).
FILES
- /dev/apm
- Power management data device. May only be opened read-only. May be opened by multiple concurrent users.
- /dev/apmctl
- Power management 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
acpi(4), intro(4), sysctl.conf(5), apm(8), apmd(8), halt(8), sysctl(8)
HISTORY
The apm
driver source code contains these
copyrights:
Copyright (c) 1995 John T. Kohl. All rights reserved.
Copyright (C) 1994 by HOSOKAWA Tatsumi <hosokawa@mt.cs.keio.ac.jp>
...and has been hacked on by many others since.
BUGS
Not all the BIOSes support power down the way we are attempting to execute it.
Not all BIOS vendors even read the specification.