You'll be wanting to build this on top of the Linux libusb stack (well, more like a thin veneer than a stack).

Here's some sample code I wrote for the VFD display that came in the Antec Fusion PC case that houses my Myth box.

http://rtr.ca/vfd_updater/

The file of interest to you is vfd_usb.c, which does all of the Right Things(tm) to detach the gizmo from any other driver before opening it for use. And so on.

EDIT: This is all original code by me, and you are free to use it as you please. No strings attached, no warranties given, no lawyers sacrificed (darn!).

Cheers

Mark