ARCH(3)

NAME

arch − 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 and DEC Alpha 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 code reads from an x86 byte I/O port.

uchar
inportb(long port)
{
    uchar data;
     if(iobfd == -1)
        iobfd = open("#P/iob", ORDWR);
     seek(iobfd, port, 0);
    if(read(iobfd, &data, sizeof(data)) != sizeof(data))
        sysfatal("inportb(0x%4.4x): %r\n", port);
    return data;
}

SOURCE

/sys/src/9/pc/devarch.c