When I first suggested using Linux in an embedded system back in 1997 while working for a hardware manufacturer, my suggestion was met with a certain degree of skepticism and surprise. Today, the use of Linux in embedded systems is no laughing matter. Indeed, many industry giants and government agencies are increasingly relying on Linux for their embedded software needs.
The widespread interest and enthusiasm generated by Linux's successful use in a number of embedded applications has led to the creation of a plethora of articles, web sites, companies, and documents all pertaining to "embedded Linux." Yet, beyond the flashy announcements, the magazine articles, and the hundreds of projects and products that claim to ease Linux's use in embedded systems, professional developers seeking a useful guide are still looking for answers to fundamental questions regarding the basic methods and techniques required to build embedded systems based on the Linux kernel.
Much of the documentation currently available relies heavily on the use of a number of prepackaged, ready-to-use cross-platform development tools and target binaries. Yet other documents cover only one very precise aspect of running Linux on an embedded target.
This book is a radical departure from the existing documentation in that it makes no assumptions as to the tools you have at hand or the scope of your project, other than your desire to use Linux. All that is required for this book is an Internet connection to download the necessary packages, browse specific online documentation, and benefit from other developers' experiences, as well as share your own, through project mailing lists. You still need a development host and documentation regarding your target's hardware, but the explanations I outline do not require the purchasing of any product or service from any vendor.
Besides giving the greatest degree of freedom and control over your design, this approach is closest to that followed by the pioneers who have spearheaded the way for Linux's use in embedded systems. In essence, these pioneers have pulled on Linux to fit their applications by stripping it down and customizing it to their purposes. Linux's penetration of the embedded world contrasts, therefore, with the approach followed by many software vendors to push their products into new fields of applications. As an embedded system developer, you are likely to find Linux much easier to pull towards your design than to adapt the products being pushed by vendors to that same design.
This book's approach is to allow you to pull Linux towards your design by providing all the details and discussing many of the corner cases encountered in using Linux in embedded systems. Though it is not possible to claim that all embedded designs are covered by this book, the resources provided here allow you to easily obtain the rest of the information required for you to customize and use Linux in your embedded system.
In writing this book, my intent has been to bring the embedded system developers who use open source and free software in their designs closer to the developers who create and maintain these open source and free software packages. Though a lot of mainstream embedded system developers, many of whom are high-caliber programmers, rely on third-party offerings for their embedded Linux needs, there is a clear opportunity for them to contribute to the open source and free software projects on which they rely. Ultimately, this sort of dynamic will ensure that Linux continues to be the best operating system choice for embedded systems.