Chapter 4 I/O Requests for Parallel and Serial Drivers

Windows NT® kernel-mode parallel drivers follow a variant of the class/port driver model:

• A device-type-specific class driver handles requests for each type of device that can communicate through a parallel port.

• A lowest-level port driver controls access to each physical parallel port.

Consequently, a single parallel port driver can have more than one parallel class driver layered above it in a given machine.

While serial drivers also might follow the class/port driver model, the system-supplied serial driver is monolithic for faster I/O throughput.