APM BIOS Driver for Linux
	$Id: README.apm_bios,v 0.3 1994/09/02 01:29:06 sfr Exp $
	by Stephen Rothwell       sfr@pdact.pd.necisa.oz.au

This driver interfaces to an Advanced Power Management (APM) BIOS on
a system (usually a laptop) to allow the control of power management
and the reporting of PM events under Linux.

Currently the driver works with Linux versions 1.1.47 , but
there should be no problems with using them with newer patch levels
of the kernel.

INSTALLATION:

There are a set of kernel patches to be applied called kernel.patch.
Use
	patch -p0 <kernel.patch	(from /usr/src)
or
	patch -p1 <kernel.patch (from /usr/src/linux)

There are also some new files to install:
	include/linux/apm_bios.h
	drivers/char/apm_bios.h
Copy these to the appropriate directories in /usr/src/linux.

Then do
	make config;make depend;make
in /usr/src/linux.

Currently there are no user level programs, but this will change shortly.

DETAILS:

The patches do the following:
	Add some descriptors to the GDT for use by the APM BIOS. (boot/head.S)
	Add code to boot/setup.S to detect the APM BIOS and register with
		it. This has to be done in real mode.
	Add the APM BIOS option to config.in.
	Add apm_bios to drivers/char/Makefile.
	Add the apm_bios_init to drivers/char/mem.c
	Add the capturing of the APM BIOS parameters in init/main.c
		These parameters are collected in boot/head.S
		while in real mode.
	Modify the scheduler (kernel/sched.c) so that the APM BIOS busy
		routine gets called when we switch away from the idle task.
	Modify the idle system call (kernel/sys.c) to call the APM BIOS
		idle routine.

The driver itself just prints some debugging information at startup
and then polls the APM BIOS every second to get events.  When it gets
a SUSPEND event, it tells the APM BIOS to suspend the system and then
when the BIOS returns, resets the system time.  If it gets a RESUME event,
it just reset the system time.  Any other event just gets logged (using
printk).

The major number for the device is dynamically allocated.  You can use
	cat /proc/devices
to find it.  Then you must use
	mknod /dev/apm_bios c <major> 0
to create the device.  This device may be read to get notification of
APM events.  Each event is returned as an unsigned short (currently in
Intel order - least significant byte first).  Select and O_NONBLOCK
also both work.

Only one process can have the device open, and only root can open the
device.