The USB Device Driver Framework

USB devices drivers are registered and deregistered at the subsystem. A driver must register 2 entry points and its name. For specific USB devices (which are not suitable to be registered at any other subsystem) a driver may register a couple of file operations and a minor number. In this case the specified minor number and the 15 following numbers are assigned to the driver. This makes it possible to serve up to 16 similar USB devices by one driver. The major number of all USB devices is 180.