Programming the Microsoft Windows Driver Model

Organization of This Book

After teaching driver programming seminars for many years, I've come to understand that people learn things in fundamentally different ways. Some people like to learn a great deal of theory about something and then learn how to apply that theory to practical problems. Other people like to learn practical things first and then learn the general theory. I call the former approach deductive and the latter approach inductive. I personally prefer an inductive approach, and I've organized this book to suit that style of learning.

My aim is to explain how to write device drivers. Broadly speaking, I want to provide the minimum background you'll need to write an actual driver and then move on to more specialized topics. That "minimum background" is pretty extensive, however; it consumes seven chapters. Once past Chapter 7, you'll be reading about topics that are important but not necessarily on the fall line that leads straight downhill to a working driver.

Chapter 1, "Beginning a Driver Project," as I've mentioned, describes WDM device drivers and how they relate to Windows itself. Along the way, I'll relate the story of how we got to where we are today in operating system and driver technology. The chapter also explains how to choose the kind of driver you need, provides an overview and checklist specifically for development managers, and addresses the issue of binary compatibility.

Chapter 2, "Basic Structure of a WDM Driver," explains the basic data structures that Windows 2000 uses to manage I/O devices and the basic way your driver relates to those data structures. I'll discuss the driver object and the device object. I'll also discuss how you write two of the subroutines the DriverEntry and AddDevice routines that every WDM driver package contains.

Chapter 3, "Basic Programming Techniques," describes the most important service functions you can call on to perform mundane programming tasks. In that chapter, I'll discuss error handling, memory management, and a few other miscellaneous tasks.

Chapter 4, "Synchronization," discusses how your driver can synchronize access to shared data in the multitasking, multiprocessor world of Windows XP. You'll learn the details about interrupt request level (IRQL) and about various synchronization primitives that the operating system offers for your use.

Chapter 5, "The I/O Request Packet," introduces the subject of input/output programming, which of course is the real reason for this book. I'll explain where I/O request packets come from, and I'll give an overview of what drivers do with them when they follow what I call the "standard model" for IRP processing. I'll also discuss the knotty subject of IRP queuing and cancellation, wherein accurate reasoning about synchronization problems becomes crucial.

Chapter 6, "Plug and Play for Function Drivers," concerns just one type of I/O request packet, namely IRP_MJ_PNP. The Plug and Play Manager component of the operating system sends you this IRP to give you details about your device's configuration and to notify you of important events in the life of your device.

Chapter 7, "Reading and Writing Data," is where we finally get to write driver code that performs I/O operations. I'll discuss how you obtain configuration information from the PnP Manager and how you use that information to prepare your driver for "substantive" IRPs that read and write data. I'll present two simple driver sample programs as well: one for dealing with a PIO device and one for dealing with a bus-mastering DMA device.

Chapter 8, "Power Management," describes how your driver participates in power management. I think you'll find, as I did, that power management is pretty complicated. Unfortunately, you have to participate in the system's power management protocols, or else the system as a whole won't work right. Luckily, the community of driver writers already has a grand tradition of cutting and pasting, and that will save you.

Chapter 9, "I/O Control Operations," contains a discussion of this important way for applications and other drivers to communicate "out of band" with your driver.

Chapter 10, "Windows Management Instrumentation," concerns a scheme for enterprisewide computer management in which your driver can and should participate. I'll explain how you can provide statistical and performance data for use by monitoring applications, how you can respond to standard WMI controls, and how you can alert controlling applications of important events when they occur.

Chapter 11, "Controller and Multifunction Devices," discusses how to write a driver for a device that embodies multiple functions, or multiple instances of the same function, in one physical device.

Chapter 12, "The Universal Serial Bus," describes how to write drivers for USB devices.

Chapter 13, "Human Interface Devices," explains how to write a driver for this important class of devices.

Chapter 14, "Specialized Topics," describes system threads, work items, error logging, and other special programming topics.

Chapter 15, "Distributing Device Drivers," tells you how to arrange for your driver to get installed on end user systems. You'll learn the basics of writing an INF file to control installation, and you'll also learn some interesting and useful things to do with the system registry. This is where to look for information about WHQL submissions too.

Chapter 16, "Filter Drivers," discusses when you can use filter drivers to your advantage and how to build and install them.

Appendix A, "Coping with Cross-Platform Incompatibilities," explains how to determine which version of the operating system is in control and how to craft a binary-compatible driver.

Appendix B, "Using WDMWIZ.AWX," describes how to use my Visual C++ application wizard to build a driver. WDMWIZ.AWX is not intended to take the place of a commercial toolkit. Among other things, that means that it's not easy enough to use that you can dispense with documentation.