The Windows Driver Model has two separate but equally important aspects. First, the core model describes the standard structure for device drivers. Second, Microsoft provides a series of bus and class drivers for common types of devices.
The core WDM model describes how device drivers are installed and started, and how they should service user requests and interact with hardware. A WDM device driver must fit into the Plug and Play (PnP) system that lets users plug in devices that can be configured in software.
Microsoft provides a series of system drivers that have all the basic functionality needed to service many standard types of device. The first type of system driver supports different types of bus, such as the Universal Serial Bus (USB), IEEE 1394 (FireWire) and Audio port devices. Other class drivers implement standard Windows facilities such as Human Input Devices (HID) and kernel streaming. Finally, the Still Image Architecture (STI) provides a framework for handling still images, scanners, etc.
These system class drivers can make it significantly easier to write some types of device driver. For example, the USB system drivers handle all the low-level communications across this bus. A well defined interface is made available to other drivers. This makes it fairly straightforward to issue requests to the USB bus.
Conclusion
Conclusion
In this book, I will explain the Windows Driver Model, including how to write device drivers that work in Windows 98 and Windows 2000. I will also cover NT style drivers that work in Windows NT 3.51 and NT 4.
A driver writer has a job completely different from a standard Windows programmer. There is much terminology to learn and each type of device has its own detailed hardware and software specifications. However, in the end, a device must be made available to Win32 programs and users.
Before writing a device driver in earnest, the next couple of chapters look at the big picture: device driver design and the crucial concepts and structures needed in the driver model.
If you are itching for something to do, order your MSDN Professional subscription. Install the MSDN library, the DDKs, and the Platform SDK. If you are writing a driver for both Windows 98 and Windows 2000, either set up a dual boot machine or get another test computer to hand.
