Special files
ppi0
through
ppi7
are used to access the devices, with the digit at the end
of the filename referring to the bus address of the device.
Current versions of the autoconf code can not probe for these
devices, so the device entry in the configuration file must be
fully qualified.
The device files appear as follows:
"crw-rw-rw- 1 root 11, 0 Dec 21 11:22 /dev/ppi"