device classes in sysfs

Has there ever been any discussion about classifying devices according to their function, and providing an interface (say with libsysfs) for user apps to enumerate a particular class? The new udev project _does_ provide the nice feature of persistent naming of a given device that can change positions on a bus (like 2 USB printers that change USB ports), but what about hunting for devices that provide the same function that can exist on any bus (like 1 parallel port printer and 1 USB printer)?

_After_ devices are configured and assigned names, users can depend on udev and friends to provide the same name to their devices. But _before_ the devices are initially configured, users (rather, writers of user apps) have to pull some special hacks to scan buses or dig deep into /proc to find what devices provide some target function (like printing).

I see /sys/class, but that seems more defined as "hardware architecture" class rather than "function" class.

Any opinions?

Tyler