When the port list will no longer be used, the program should call
ieee1284_free_ports
giving it a pointer to the
parport_list
structure that holds the list of ports returned by
ieee1284_find_ports(3). The ports are reference counted with the
ieee1284_open
and
ieee1284_close
functions, and so the port list may be freed even if it contains pointers to ports that are still open.