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.). 44This function is available only on systems whose APM 45supports CPU idling. 46.It 47.Nm 48exports an application interface as a character device. 49Applications 50can control APM, or retrieve APM status information via this interface. 51.Nm 52exports the following interfaces. 53These symbols are defined in 54.In machine/apm_bios.h . 55.Bl -tag -width 4n -offset indent 56.It Sy APMIO_SUSPEND 57Suspend system. 58.It Sy APMIO_GET 59Get power management information. 60.It Sy APMIO_ENABLE 61.It Sy APMIO_DISABLE 62Enable / Disable power management. 63.It Sy APMIO_HALTCPU 64.It Sy APMIO_NOTHALTCPU 65Control execution of HLT in the kernel context switch routine. 66.It Sy APMIO_GETPWSTATUS 67Get per battery information. 68.Pp 69Some APM implementations execute the HLT 70(Halt CPU until an interrupt occurs) 71instruction in the 72.Dq Em Idle CPU 73call, while others do not. 74Thus enabling this may result in 75redundant HLT executions because 76.Dq Em Idle CPU 77is called from the kernel context switch routine that inherently executes 78HLT. 79This may reduce peak system performance. 80.Pp 81Also the system hangs up if HLT instruction is disabled in the kernel 82context switch routine, and if the APM implementation of the machine 83does not execute HLT in 84.Dq Em Idle CPU . 85On some implementations that do not support CPU clock slowdown, APM 86might not execute HLT. 87.Nm 88disables 89.Sy APMIO_NOTHALTCPU 90operation on such machines. 91.Pp 92The current version of 93.Nm 94does not call 95.Dq Em Idle CPU 96from the kernel context switch routine if clock slowdown is not supported, 97and it executes HLT instruction by default. 98Therefore, there is 99no need to use these two operations in most cases. 100.El 101.Pp 102These interfaces are used by 103.Xr apm 8 . 104.It 105.Nm 106polls APM events and handles the following events. 107.Bl -column PMEV_POWERSTATECHANGEXXX "suspend system xxxxx" 108.It Sy "Name " "Action " "Description" 109.It Dv "PMEV_STANDBYREQ " No "suspend system " "standby request" 110.It Dv "PMEV_SUSPENDREQ " No "suspend system " "suspend request" 111.It Dv "PMEV_USERSUSPENDREQ " No "suspend system " "user suspend request" 112.It Dv "PMEV_CRITSUSPEND " No "suspend system " "critical suspend request" 113.It Dv "PMEV_NORMRESUME " No "resume system " "normal resume" 114.It Dv "PMEV_CRITRESUME " No "resume system " "critical resume" 115.It Dv "PMEV_STANDBYRESUME " No "resume system " "standby resume" 116.It Dv "PMEV_BATTERYLOW " No "notify message " "battery low" 117.It Dv "PMEV_UPDATETIME " No "adjust clock " "update time" 118.El 119.El 120.Sh SEE ALSO 121.Xr apm 8 , 122.Xr zzz 8 123.Sh AUTHORS 124Tatsumi Hosokawa <hosokawa@jp.FreeBSD.org> 125.Sh BUGS 126WARNING! 127Many, if not most, of the implementations of APM-bios in laptops 128today are buggy. 129You may be putting your LCD-display and batteries at 130a risk by using this interface. 131(The reason this is not a problem for 132MS-Windows is that they use the real-mode interface.) 133If you see any 134weird behavior from your system with this code in use, unplug the 135power and batteries ASAP, if not immediately, and disable this code. 136.Pp 137We are very interested in getting this code working, so please send your 138observations of any anomalous behavior to us. 139.Pp 140When 141.Nm 142is active, calling the BIOS setup routine by using hot-keys, 143may cause serious trouble when resuming the system. 144BIOS setup programs should be called during bootstrap, or from DOS. 145.Pp 146Some APM implementations cannot handle events such as pushing the 147power button or closing the cover. 148On such implementations, the system 149.Ar must 150be suspended 151.Ar only 152by using 153.Xr apm 8 154or 155.Xr zzz 8 . 156.Pp 157Disk spin-down, LCD backlight control, and power on demand have not 158been supported on the current version. 159