bind -a #P /dev 
 /dev/cputype  /dev/ioalloc  /dev/iob  /dev/iol  /dev/iow  /dev/irqalloc 
 DESCRIPTION
This device presents textual information about PC hardware and allows
user-level control of the I/O ports on x86-class machines.

Reads from
 cputype recover the processor type and clock rate.

Reads from
 ioalloc return I/O ranges used by each device, one line
per range. Each line contains three fields separated by white space: first address
in hexadecimal,
last address, name of device.

Reads from
 irqalloc return the enabled interrupts, one line per
interrupt. Each line contains three fields separated by white space:
the trap number, the IRQ it is assigned to, and the name of
the device using it.

Reads and writes to
 iob ,  iow , and
 iol cause 8-bit wide, 16-bit wide, and 32-bit wide requests to
I/O ports.
The port accessed is determined by the byte offset of the
file descriptor.
 EXAMPLE
The following Limbo code reads from an x86 byte I/O port.
.EX
inportb(port: int): byte
{
 data := array[1] of byte;

 if(iobfd == nil)
 iobfd = sys->open("#P/iob", Sys->ORDWR);

 sys->seek(iobfd, port, 0);
 if(sys->read(iobfd, data, len data) != len data)
 fatal(sys->sprint("inportb(16r%4.4x): %r\en", port));
 return data[0];
}

 SOURCE
 /os/pc/devarch.c