"Writing Windows WDM Device Drivers" - читать интересную книгу автора (Cant Chris)

Chapter 1 Introduction

In this book, I will tell you how to write some types of device driver for Windows. I will primarily describe the Windows Driver Model for Windows 98 and Windows 2000. Additionally, I will cover device drivers that also run in Windows NT 3.51 and NT 4, which I call "NT style" drivers.

A device driver provides a software interface to hardware connected to a computer. It is a trusted part of the operating system. User application programs can access hardware in a well-defined manner, without having to worry about how the hardware must be controlled. For example, a disk driver might hide the fact that data must be written in 512-byte chunks. A driver is a piece of software that becomes part of the operating system kernel when it is loaded. A driver makes one or more devices available to the user mode programmer, each representing a physical or logical piece of hardware. For example, one physical hard disk may be viewed as two logical disks called C: and D:.

In Windows, a driver always makes a device look like a file. A handle to the device can be opened. An application program can then issue read and write requests to the driver, before the device handle is finally closed.

Clearly, there are many pieces of hardware that are essentially alike, because they share a bus or do similar tasks. Microsoft provides several generic drivers that perform these common tasks. Device drivers can use the facilities of these standard drivers. This approach makes it easier to share a common bus, and makes it simpler to write new drivers.

The task of writing a new driver, therefore, often starts by identifying which generic drivers can be used. A stack of drivers, layered one on top of each other, processes user requests in stages. A low-level bus driver might be used to handle all the basic communication with hardware. An intermediate class driver might provide the facilities that are common to a whole category of devices.

In Windows 98 and Windows 2000, device drivers must be designed according to the Windows Driver Model (WDM), which I describe in the following section. WDM is based on the device driver model used in Windows NT 4 and NT 3.51.