ieee1284_ref man page
ieee1284_ref, ieee1284_unref — modify a port's reference count
int ieee1284_ref(struct parport *port);
int ieee1284_unref(struct parport *port);
If you want to free the port list from ieee1284_find_ports but open one of the ports later on, you will need to prevent it from being destroyed in ieee1284_free_ports. Each port has a reference count, and you can use ieee1284_ref to increment it and ieee1284_unref to decrement it.
If you use ieee1284_ref at any stage, you must later call ieee1284_unref to relinquish the extra reference. If you do not do this, the resources associated with the port will not be cleaned up.
If you have not previously used ieee1284_ref on a port, you must not use ieee1284_unref on it.
These functions return the number of references held after the increment or decrement.
Tim Waugh <firstname.lastname@example.org>
Copyright © 2001-2003 Tim Waugh
The man page ieee1284_unref(3) is an alias of ieee1284_ref(3).