Book Image

Mastering Embedded Linux Programming - Third Edition

By : Frank Vasquez, Chris Simmonds
5 (3)
Book Image

Mastering Embedded Linux Programming - Third Edition

5 (3)
By: Frank Vasquez, Chris Simmonds

Overview of this book

If you’re looking for a book that will demystify embedded Linux, then you’ve come to the right place. Mastering Embedded Linux Programming is a fully comprehensive guide that can serve both as means to learn new things or as a handy reference. The first few chapters of this book will break down the fundamental elements that underpin all embedded Linux projects: the toolchain, the bootloader, the kernel, and the root filesystem. After that, you will learn how to create each of these elements from scratch and automate the process using Buildroot and the Yocto Project. As you progress, the book will show you how to implement an effective storage strategy for flash memory chips and install updates to a device remotely once it’s deployed. You’ll also learn about the key aspects of writing code for embedded Linux, such as how to access hardware from apps, the implications of writing multi-threaded code, and techniques to manage memory in an efficient way. The final chapters demonstrate how to debug your code, whether it resides in apps or in the Linux kernel itself. You’ll also cover the different tracers and profilers that are available for Linux so that you can quickly pinpoint any performance bottlenecks in your system. By the end of this Linux book, you’ll be able to create efficient and secure embedded devices using Linux.
Table of Contents (27 chapters)
1
Section 1: Elements of Embedded Linux
10
Section 2: System Architecture and Design Decisions
18
Section 3: Writing Embedded Applications
22
Section 4: Debugging and Optimizing Performance

Selecting the best idle state

When a processor has no more work to do, it executes a halt instruction and enters
an idle state. While idle, the CPU uses less power. It exits the idle state when an event
such as a hardware interrupt occurs. Most CPUs have multiple idle states that use
varying amounts of power. Usually, there is a trade-off between the power usage and the latency, or the length of time, it takes to exit the state. In the ACPI specification, they are called C-states.

In the deeper C-states, more circuitry is turned off at the expense of losing some state, and so it takes longer to return to normal operation. For example, in some C-states the CPU caches may be powered off, and so when the CPU runs again, it may have to reload some information from the main memory. This is expensive, and so you only want to do this if there is a good chance that the CPU will remain in this state for some time. The number of states varies from one system to another. Each takes some time...