Comment in linux/drivers/usb/acm.c
* ... Did some
* testing at 3Com => zmodem uload+download works, pppd had trouble but
* seems to work now. Changed Menuconfig texts "Communications Device
* Class (ACM)" might be a bit more intuitive.

Should work linux to linux when the linux USB driver is available. Presumably
there is something for windows too but... who cares?

Paul