I've been investigating this, recently, and to my knowledge usb gps units are not supported by the linux software outthere,
though I'd be happy to be proven wrong.
Alot of the linux gps software outthere seems to be pretty old, and supports serial connections, which, on the face of it,
would seem to eliminate them as software that would provide good support of the new usb gps units.
OTOH, usb _is_ a serial protocol, and it may be just a matter of a proper udev rule to create a device the non-usb
software wants to use. I'm not sure whether an app must "speak usb" or not, though, I believe it probably does.
Here's a sourceforge search results page
http://sourceforge.net/search/?type_of_ ... rds=garmin