1130b656e5
This will make a number of things easier in the future, as well as (finally!) avoiding the Id-smashing problem which has plagued developers for so long. Boy, I'm glad we're not using sup anymore. This update would have been insane otherwise.
149 lines
4.8 KiB
Groff
149 lines
4.8 KiB
Groff
.\" LP (Laptop Package)
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.\"
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.\" Copyright (c) 1994 by HOSOKAWA, Tatsumi <hosokawa@mt.cs.keio.ac.jp>
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.\"
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.\" This software may be used, modified, copied, and distributed, in
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.\" both source and binary form provided that the above copyright and
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.\" these terms are retained. Under no circumstances is the author
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.\" responsible for the proper functioning of this software, nor does
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.\" the author assume any responsibility for damages incurred with its
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.\" use.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd November 1, 1994
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.Dt APM 4 i386
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.Os
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.Sh NAME
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.Nm apm
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.Nd APM BIOS interface
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.Sh SYNOPSIS
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.Cd device apm0 at isa?
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.Sh DESCRIPTION
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.Nm apm
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is an interface to the Intel / Microsoft APM (Advanced Power Management) BIOS
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on laptop PCs.
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.Pp
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.Nm apm
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provides the following power management functions.
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.Bl -enum -offset indent
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.It
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When the system wakes up from suspended mode,
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.Nm apm
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adjusts the system clock to RTC.
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.It
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When the system wakes up from suspended mode,
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.Nm apm
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passes a message to
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.Xr syslogd 8
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comprising of system wakeup time and elapsed time during suspended mode.
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.It
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.Nm apm
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slows CPU clock when there are no system activities (runnable processes,
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interrupts, etc.). This function is available only on systems whose APM
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supports CPU idling.
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.It
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.Nm apm
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exports an application interface as a character device. Applications
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can control APM, or retrieve APM status information via this interface.
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.Nm apm
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exports the following interfaces. These symbols are defined in
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.Dq Pa /usr/include/machine/apm_bios.h.
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.Bl -tag -width 4n -offset indent
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.It Sy APMIO_SUSPEND
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Suspend system.
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.It Sy APMIO_GET
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Get power management information.
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.It Sy APMIO_ENABLE
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.It Sy APMIO_DISABLE
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Enable / Disable power management.
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.It Sy APMIO_HALTCPU
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.It Sy APMIO_NOTHALTCPU
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Control execution of HLT in the kernel context switch routine.
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.Pp
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Some APM implementations execute the HLT
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.Pq Halt CPU until an interrupt occurs
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instruction in the
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.Dq Pa Idle CPU
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call, while others do not. Thus enabling this may result in
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redundant HLT executions because
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.Dq Pa Idle CPU
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is called from the kernel context switch routine that inherently executes
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HLT. This may reduce peak system performance.
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.Pp
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Also the system hangs up if HLT instruction is disabled in the kernel
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context switch routine, and if the APM implementation of the machine
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does not execute HLT in
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.Dq Pa Idle CPU.
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On some implementations that do not support CPU clock slowdown, APM
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might not execute HLT.
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.Nm apm
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disables
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.Sy APMIO_NOTHALTCPU
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operation on such machines.
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.Pp
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The current version of
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.Nm apm
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does not call
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.Dq Pa Idle CPU
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from the kernel context switch routine if clock slowdown is not supported,
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and it executes HLT instruction by default. Therefore, there is
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no need to use these two operations in most cases.
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.El
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.Pp
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These interfaces are used by
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.Xr apm 8
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and
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.Xr apmconf 8 .
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.It
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.Nm apm
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polls APM events and handles the following events.
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.Bl -column PMEV_POWERSTATECHANGEXXX "suspend system xxxxx"
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.It Sy "Name " "Action " "Description"
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.It Dv "PMEV_STANDBYREQ " No "suspend system " "standby request"
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.It Dv "PMEV_SUSPENDREQ " No "suspend system " "suspend request"
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.It Dv "PMEV_USERSUSPENDREQ " No "suspend system " "user suspend request"
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.It Dv "PMEV_CRITSUSPEND " No "suspend system " "critical suspend request"
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.It Dv "PMEV_NORMRESUME " No "resume system " "normal resume"
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.It Dv "PMEV_CRITRESUME " No "resume system " "critical resume"
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.It Dv "PMEV_STANDBYRESUME " No "resume system " "standby resume"
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.It Dv "PMEV_BATTERYLOW " No "notify message " "battery low"
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.It Dv "PMEV_UPDATETIME " No "adjust clock " "update time"
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.El
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.El
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.Sh BUGS
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WARNING! Many, if not most, of the implementations of APM-bios in laptops
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today are buggy. You may be putting your LCD-display and batteries at
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a risk by using this interface. (The reason this isn't a problem for
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MS-windows is that they use the real-mode interface.) If you see any
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weird behaviour from your system with this code in use, unplug the
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power and batteries ASAP, if not imidiately, and disable this code.
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.Pp
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We are very interested in getting this code working, so please send you
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observations of any anormalous behaviour to us.
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.Pp
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When
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.Nm apm
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is active, calling the BIOS setup routine by using hotkeys,
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may cause serious trouble when resuming the system.
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BIOS setup programs should be called during bootstrap, or from DOS.
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.Pp
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Some APM implementations cannot handle events such as pushing the
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power button or closing the cover. On such implementations, the system
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.Ar must
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be suspended
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.Ar only
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by using
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.Xr apm 8
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or
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.Xr zzz 8 .
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.Pp
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Disk spindown, LCD backlight control, and power on demand have not
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been supported on the current version.
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.Sh SEE ALSO
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.Xr apm 8 ,
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.Xr apmconf 8 ,
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.Xr zzz 8
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.Sh AUTHOR
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HOSOKAWA, Tatsumi <hosokawa@mt.cs.keio.ac.jp> (Keio Univ., Japan)
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