Classes

The bus-oriented device model is good for the kernel
Provides the needed topology information

It is less useful for users
They rarely care how a device is connected
More interested in what types of devices exist
"Where is the mouse on this system?"

The class hierarchy meets this need
Reorganizes resources according to type
Not just devices
Allows consistent view of diverse devices
"Interfaces" for class attribute setup
Classes create hotplug events

See the web site for details