Preface
Linux has been the mainstay of embedded computing for many years. And yet, there are remarkably few books that cover the topic as a whole: this book is intended to fill that gap. The term "embedded Linux" is not well defined and can be applied to the operating system inside a wide range of devices ranging from thermostats to Wi-Fi routers to industrial control units. However, they are all built on the same basic open source software. Those are the technologies that I describe in this book, based on my experience as an engineer and the materials I have developed for my training courses.
Technology does not stand still. The industry based around embedded computing is just as susceptible to Moore's law as mainstream computing. The exponential growth that this implies has meant that a surprisingly large number of things have changed since the first edition of this book was published. This third edition is fully revised to use the latest versions of the major open source components, which include Linux 5.4, the Yocto Project 3.1 Dunfell, and Buildroot 2020.02 LTS. In addition to Autotools, the book now covers CMake, a modern build system that has seen increased adoption in recent years.
Mastering Embedded Linux Programming covers the topics in roughly the order that you will encounter them in a real-life project. The first eight chapters are concerned with the early stages of the project, covering basics such as selecting the toolchain, the bootloader, and the kernel. I introduce the idea of embedded build systems, using Buildroot and the Yocto Project as examples. The section ends with new in-depth coverage of the Yocto Project.
Section 2, Chapters 9 to 15, looks at the various design decisions that need to be made before development can take place in earnest. It covers the topics of filesystems, software update, device drivers, the init program, and power management. Chapter 12 demonstrates various techniques for rapid prototyping with a breakout board, including how to read schematics, solder headers, and troubleshoot signals using a logic analyzer. Chapter 14 is a deep dive into Buildroot where you will learn how to partition your system software into separate services using BusyBox runit.
Section 3, Chapters 16, 17, and 18, will help you in the implementation phase of the project. We start with Python packaging and dependency management, a topic of growing importance as machine learning applications continue to take the world by storm. Next, we move on to various forms of inter-process communication and multithreaded programming. The section concludes with a careful examination of how Linux manages memory and demonstrates how to measure memory usage and detect memory leaks using the various tools that are available.
The fourth section, which includes Chapters 19 and 20, shows you how to make effective use of the many debug and profiling tools that Linux has to offer in order to detect problems and identify bottlenecks. Chapter 19 now describes how to configure Visual Studio Code for remote debugging using GDB. Chapter 20 now includes coverage of BPF, a new technology that enables advanced programmatic tracing inside the Linux kernel. The final chapter brings together several threads to explain how Linux can be used in real-time applications.
Each chapter introduces a major area of embedded Linux. It describes the background so that you can learn the general principles, but it also includes detailed working examples that illustrate each of these areas. You can treat this as a book of theory, or a book of examples. It works best if you do both: understand the theory and try it out in real life.
