This practical guide is for anyone who wants to support computer peripherals or develop new hardware to run under the Linux operating system. It shows how to write drivers for a wide range of devices, revealing information previously shared only by word of mouth or in cryptic source code comments. Version 2.4 of the Linux kernel includes significant changes to device drivers, simplifying many activities but providing subtle new features that can make a driver both more efficient and more flexible. Major changes covered in the second edition include symmetric multiprocessing (SMP) and locking, new CPUs, and recently supported buses. For those who are curious about how an operating system does its job, this book provides insights into address spaces, asynchronous events, and I/O. The second edition is centered on Kernel 2.4, but includes information for kernels back to 2.0 where feasible.