device classes in sysfs

[Tyler Hall <tyler_hall@sympatico.ca>]

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