ARCH(3)ARCH(3)NAMEarch - x86 architecture-specific information and control
SYNOPSIS
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 inter‐
rupt. 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.
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\n", port));
return data[0];
}
SOURCE
/os/pc/devarch.c
x86 ARCH(3)
