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.\" $FreeBSD$ 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 apm 22.Sh DESCRIPTION 23.Nm 24is an interface to the Intel / Microsoft APM (Advanced Power Management) BIOS 25on laptop PCs. 26.Pp 27.Nm 28provides the following power management functions. 29.Bl -enum -offset indent 30.It 31When the system wakes up from suspended mode, 32.Nm 33adjusts the system clock to RTC. 34.It 35When the system wakes up from suspended mode, 36.Nm 37passes a message to 38.Xr syslogd 8 39comprising of system wakeup time and elapsed time during suspended mode. 40.It 41.Nm 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 47exports an application interface as a character device. Applications 48can control APM, or retrieve APM status information via this interface. 49.Nm 50exports the following interfaces. These symbols are defined in 51.In 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.It Sy APMIO_GETPWSTATUS 64Get per battery information. 65.Pp 66Some APM implementations execute the HLT 67(Halt CPU until an interrupt occurs) 68instruction in the 69.Dq Em Idle CPU 70call, while others do not. Thus enabling this may result in 71redundant HLT executions because 72.Dq Em Idle CPU 73is called from the kernel context switch routine that inherently executes 74HLT. This may reduce peak system performance. 75.Pp 76Also the system hangs up if HLT instruction is disabled in the kernel 77context switch routine, and if the APM implementation of the machine 78does not execute HLT in 79.Dq Em Idle CPU . 80On some implementations that do not support CPU clock slowdown, APM 81might not execute HLT. 82.Nm 83disables 84.Sy APMIO_NOTHALTCPU 85operation on such machines. 86.Pp 87The current version of 88.Nm 89does not call 90.Dq Em Idle CPU 91from the kernel context switch routine if clock slowdown is not supported, 92and it executes HLT instruction by default. Therefore, there is 93no need to use these two operations in most cases. 94.El 95.Pp 96These interfaces are used by 97.Xr apm 8 . 98.It 99.Nm 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 behavior from your system with this code in use, unplug the 120power and batteries ASAP, if not immediately, and disable this code. 121.Pp 122We are very interested in getting this code working, so please send you 123observations of any anomalous behavior to us. 124.Pp 125When 126.Nm 127is active, calling the BIOS setup routine by using hot-keys, 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 spin-down, 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 zzz 8 146.Sh AUTHORS 147Tatsumi Hosokawa <hosokawa@jp.FreeBSD.org> 148