Writing Layered Drivers

Layered drivers are the most general type of intermediate driver. They depend on a well-defined inter-driver calling mechanism provided by the I/O Manager. The following three sections explain how this mechanism works and what a driver needs to do if it wants to use another driver as a component.

How Layered Drivers Work

As shown in Figure 15.1, a layered driver may expose one or more named Device objects to which clients send I/O requests. When an IRP representing one of these requests arrives, the layered driver can proceed in two different ways.

  • Send the IRP directly to a lower-level driver.

  • Hold the IRP in a pending state while it allocates additional IRPs and sends them to one or more lower-level drivers.

If the ...

Get Windows® 2000 Device Driver Book: A Guide for Programmers, Second Edition, The now with O’Reilly online learning.

O’Reilly members experience live online training, plus books, videos, and digital content from 200+ publishers.