What's the difference between the device driver "side" and the PC "side"? In my view, both are on the same "side" since the processor on the PC executes the device driver.
I'm not clear either on what exactly the USB device does. I had two thoughts that made me think the USB device might actually be doing something.
First is U3. Years ago, USB devices would include software on it that would be executed by the PC but only use the USB device rather than the PC's storage. For example, it would have a localized version of Firefox and Thunderbird on the USB device with all your bookmarks, history, contact list, e-mail correspondence, etc. So, you plug in the device at a PC in a hotel lobby or library or borrowed from a friend and it becomes your computer temporarily. Kinda cool, IMO.
Something about it caused the computer to execute code on the USB drive and the USB drive dictated the behavior of the PC. I think you can craft claims covering just the USB device in that case.
Second is eye-fi, an SD card with wifi capability. While not a USB device (without an adapter), it has "logic" on it, not just dumb storage. In fact, USB web cams have processors in them, as do other USB devices. So, I assumed it was possible that the USB device is not just a dumb storage device and that the logic on the USB device itself could have novel logic on it.
However, if neither of those is true and the USB device is really just a dumb storage device and all of the novelty is what the PC does with it (even if there's a custom driver on the PC that does novel things with USB storage devices), Karen's right, all the novel stuff would likely be on the PC exclusively.
Regards.