While most portions of an operating system are maintained and developed by individuals who specialize in a given operating system, device drivers are unique: They’re maintained by a much broader spectrum of developers. Some device driver authors have extensive experience with a particular operating system, while others have detailed knowledge of specific hardware components and are tasked with maintaining device drivers for those components across multiple systems. Too, device drivers are often somewhat self-contained, so that a developer can maintain a device driver while viewing other parts of the system as a black box.

Of course, that black box still has an interface, and each operating system provides its own set of interfaces to device drivers. Device drivers on all systems need to perform many common tasks, such as discovering devices, allocating resources for connected devices, and managing asynchronous events. However, each operating system has its own ways of dealing with these tasks, and each differs in the interfaces it provides for higher-level tasks. The key to writing a device driver that is both robust and efficient lies in understanding the specific details of the interfaces that the particular operating system provides.

FreeBSD Device Drivers is an excellent guide to the most commonly used FreeBSD device driver interfaces. You’ll find coverage of lower-level interfaces, including attaching to eligible devices and managing device resources, as well as higher-level interfaces, such as interfacing with the network and storage stacks. In addition, the book’s coverage of several of the APIs available in the kernel environment, such as allocating memory, timers, and synchronization primitives, will be useful to anyone working with the FreeBSD kernel. This book is a welcome resource for FreeBSD device driver authors.

John Baldwin

Kernel Developer, FreeBSD

New York

March 20, 2012