arch – architecture–specific information and control
bind –a #P /dev
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 in
MHz. Reads from archctl yield at least data of this form:
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.
The following code reads from an x86 byte I/O port.