When accessing the hardware directly, one of the most common operations is to read and write to hardware IO ports.

There is an accessor function (and compiler-macro) located in losp/muerte/io-ports.lisp.  This accessor establishes an easy to use method of using IO ports.

Reading from an IO port is accomplished through the following function call:

(io-port <address> <data-type>)

Where:

  * <address> is the io-port address.
  * <data-type> is one of the following:
    * :unsigned-byte8 - an 8-bit integer (using inb/outb).
    * :unsigned-byte16 - a 16-bit integer (inw/outw).
    * :unsigned-byte32 - a 32-bit integer (ind/outd).
    * :character - an 8-bit character (inb/outb).
    * :location - a fixnum, i.e. a lispval whose lower two bits are forced to zero (ind/outd).

To write to an IO port you use the following construction

(setf (io-port <address> <data-type>) <value>)

Where <address> and <data-type> are from the same types are IO port reads and <value> is the data you wish to write to the port.