Class Driver and Minidriver Definitions

A Microsoft-provided class driver is an intermediate driver designed to provide a simple interface between a vendor-written minidriver and the operating system. A minidriver is a hardware-specific DLL that uses a Microsoft-provided class driver to accomplish most actions through function calls, and provides only device-specific controls.

Under WDM, the minidriver registers its associated hardware adapters with the class driver, and the class driver creates a file object to represent each adapter that registers. The minidriver uses the class driver's device object to make system calls. The class driver is accessed by user-mode clients through WDM Streaming.

The interactions between class driver and minidriver include:

• The minidriver does not create a device object, but shares the class driver's device object as necessary. This saves system resources.

• Only one device object is created per adapter. Multiple subdevices (called streams) supported by the adapter are represented by WDM Streaming pins.