1.\" LP (Laptop Package) 2.\" 3.\" Copyright (c) 1994 by HOSOKAWA, Tatsumi <hosokawa@mt.cs.keio.ac.jp> 4.\" 5.\" This software may be used, modified, copied, and distributed, in 6.\" both source and binary form provided that the above copyright and 7.\" these terms are retained. Under no circumstances is the author 8.\" responsible for the proper functioning of this software, nor does 9.\" the author assume any responsibility for damages incurred with its 10.\" use. 11.\" 12.\" $Id$ 13.\" 14.Dd November 1, 1994 15.Dt APM 4 i386 16.Os 17.Sh NAME 18.Nm apm 19.Nd APM BIOS interface 20.Sh SYNOPSIS 21.Cd device apm0 at isa? 22.Sh DESCRIPTION 23.Nm apm 24is an interface to the Intel / Microsoft APM (Advanced Power Management) BIOS 25on laptop PCs. 26.Pp 27.Nm apm 28provides the following power management functions. 29.Bl -enum -offset indent 30.It 31When the system wakes up from suspended mode, 32.Nm apm 33adjusts the system clock to RTC. 34.It 35When the system wakes up from suspended mode, 36.Nm apm 37passes a message to 38.Xr syslogd 8 39comprising of system wakeup time and elapsed time during suspended mode. 40.It 41.Nm apm 42slows CPU clock when there are no system activities (runnable processes, 43interrupts, etc.). This function is available only on systems whose APM 44supports CPU idling. 45.It 46.Nm apm 47exports an application interface as a character device. Applications 48can control APM, or retrieve APM status information via this interface. 49.Nm apm 50exports the following interfaces. These symbols are defined in 51.Dq Pa /usr/include/machine/apm_bios.h. 52.Bl -tag -width 4n -offset indent 53.It Sy APMIO_SUSPEND 54Suspend system. 55.It Sy APMIO_GET 56Get power management information. 57.It Sy APMIO_ENABLE 58.It Sy APMIO_DISABLE 59Enable / Disable power management. 60.It Sy APMIO_HALTCPU 61.It Sy APMIO_NOTHALTCPU 62Control execution of HLT in the kernel context switch routine. 63.Pp 64Some APM implementations execute the HLT 65.Pq Halt CPU until an interrupt occurs 66instruction in the 67.Dq Pa Idle CPU 68call, while others do not. Thus enabling this may result in 69redundant HLT executions because 70.Dq Pa Idle CPU 71is called from the kernel context switch routine that inherently executes 72HLT. This may reduce peak system performance. 73.Pp 74Also the system hangs up if HLT instruction is disabled in the kernel 75context switch routine, and if the APM implementation of the machine 76does not execute HLT in 77.Dq Pa Idle CPU. 78On some implementations that do not support CPU clock slowdown, APM 79might not execute HLT. 80.Nm apm 81disables 82.Sy APMIO_NOTHALTCPU 83operation on such machines. 84.Pp 85The current version of 86.Nm apm 87does not call 88.Dq Pa Idle CPU 89from the kernel context switch routine if clock slowdown is not supported, 90and it executes HLT instruction by default. Therefore, there is 91no need to use these two operations in most cases. 92.El 93.Pp 94These interfaces are used by 95.Xr apm 8 96and 97.Xr apmconf 8 . 98.It 99.Nm apm 100polls APM events and handles the following events. 101.Bl -column PMEV_POWERSTATECHANGEXXX "suspend system xxxxx" 102.It Sy "Name " "Action " "Description" 103.It Dv "PMEV_STANDBYREQ " No "suspend system " "standby request" 104.It Dv "PMEV_SUSPENDREQ " No "suspend system " "suspend request" 105.It Dv "PMEV_USERSUSPENDREQ " No "suspend system " "user suspend request" 106.It Dv "PMEV_CRITSUSPEND " No "suspend system " "critical suspend request" 107.It Dv "PMEV_NORMRESUME " No "resume system " "normal resume" 108.It Dv "PMEV_CRITRESUME " No "resume system " "critical resume" 109.It Dv "PMEV_STANDBYRESUME " No "resume system " "standby resume" 110.It Dv "PMEV_BATTERYLOW " No "notify message " "battery low" 111.It Dv "PMEV_UPDATETIME " No "adjust clock " "update time" 112.El 113.El 114.Sh BUGS 115WARNING! Many, if not most, of the implementations of APM-bios in laptops 116today are buggy. You may be putting your LCD-display and batteries at 117a risk by using this interface. (The reason this isn't a problem for 118MS-windows is that they use the real-mode interface.) If you see any 119weird behaviour from your system with this code in use, unplug the 120power and batteries ASAP, if not imidiately, and disable this code. 121.Pp 122We are very interested in getting this code working, so please send you 123observations of any anormalous behaviour to us. 124.Pp 125When 126.Nm apm 127is active, calling the BIOS setup routine by using hotkeys, 128may cause serious trouble when resuming the system. 129BIOS setup programs should be called during bootstrap, or from DOS. 130.Pp 131Some APM implementations cannot handle events such as pushing the 132power button or closing the cover. On such implementations, the system 133.Ar must 134be suspended 135.Ar only 136by using 137.Xr apm 8 138or 139.Xr zzz 8 . 140.Pp 141Disk spindown, LCD backlight control, and power on demand have not 142been supported on the current version. 143.Sh SEE ALSO 144.Xr apm 8 , 145.Xr apmconf 8 , 146.Xr zzz 8 147.Sh AUTHOR 148HOSOKAWA, Tatsumi <hosokawa@mt.cs.keio.ac.jp> (Keio Univ., Japan) 149