bind -a #P /dev 
 /dev/apm 
 DESCRIPTION

This device presents a low-level interface to
the APM 1.2 bios calls.
It is enabled by adding the line
 `` apm0= '' to 
 plan9.ini . (The value after the equals sign is ignored; the presence of
the line at all enables the driver.)
It is only available on uniprocessor PCs.
Writing a 386
 Ureg structure and then reading it back executes an APM call:
the written registers are passed to the call,
and the read registers are those returned by the call.
 .PP
 In addition, the following strings may be
 written to
 .B /dev/apm
 to negotiate with other kernel devices about
 suspension of the system.
 .TP
 .B "vote suspend
 Poll kernel devices for objections to suspending the system.
 The write succeeds only when no device objected.
 .TP
 .B "abort suspend
 Notify kernel devices that the vote failed and the
 suspension will not happen.
 .TP
 .B "commit suspend
 Notify kernel devices that the vote succeeded and
 suspension will happen. The devices
 may take measures such as disabling PCMCIA cards.
 .TP
 .B "resume suspend
 Notify kernel devices that the system has come back
 after a suspension.
 The devices may take measures such as reenabling PCMCIA cards.
 .PD
 A similar set of messages governs entrance into
 .B standby
 mode.

This device is intended to enable more user-friendly
interfaces such as 
 apm (8). 
 SOURCE
 /sys/src/9/pc/apm.c 

 /sys/src/9/pc/apmjump.s