The Linux kernel is at the heart of a large number of embedded products being designed today. Over the last 10 years, this operating system has developed from dominating the server market to being the most used operating system in embedded systems, even those with real-time requirements. On the way, Linux has evolved, and the embedded industry has realized it has some key and unique characteristics:
Linux is quick to adapt to new technologies and it's the place where innovation happens first
It is robust, and the development community is quick to react to problems
It is secure, and vulnerabilities are discovered and dealt with in a much quicker way than in competing proprietary products
It is open, which means your company is able to own, modify, and understand the technology
Finally, Linux is free
All of these make it a very compelling choice for embedded development.
But at the same time, an embedded Linux product is not only the Linux kernel. Companies need to build an embedded system over the operating system, and that's where embedded Linux was finding it difficult to make its place—until Yocto arrived.
The Yocto Project brings all the benefits of Linux into the development of embedded systems. It provides a standard build system that allows you to develop embedded products in a quick, reliable, and controlled way. Just as Linux has its strong points for embedded development, Yocto has its own too:
Yocto is secure, as it uses recent sources and provides the means to quickly apply security vulnerabilities to your products
It is robust, as it is used by a large community, which is quick to react to problems
It is open, so your company can own the technology, understand it, and make it fit for specific needs
It is free
With the Yocto Project's 6-month stable release process, package management updates, and flexibility, you will be able to focus on your embedded application, knowing that you are building it on top of a trusted system. You will speed up your development cycles and produce outstanding products.
But Yocto is a new technology, and developers need to adapt to it. This books aims to provide a practical guide for readers with basic knowledge of Linux and Yocto to develop a production-ready industrial system based on the ARM architecture.
Chapter 1, The Build System, describes the use of the Poky build system and extends it with the Freescale BSP community layer. It also describes common build system configurations and features used to optimize the building of target images.
Chapter 2, The BSP Layer, guides you through the customization of the BSP for your own product. It then explains how to configure, modify, build, and debug the U-Boot bootloader, the Linux kernel, and its device tree.
Chapter 3, The Software Layer, describes the process of creating a new software layer to hold new applications, services, or modifications to existing packages, as well as discussing a release process for license compliance.
Chapter 4, Application Development, starts with toolchains and the Application Development Toolkit (ADT), and deals with application development in detail, including development environments such as Eclipse and Qt creator.
Chapter 5, Debugging, Tracing, and Profiling, discusses debugging tools and techniques, and explores the tracing functionalities offered by the Linux kernel, along with some of the user-space-tracing and profiling tools that make use of them.
This book assumes some basic working knowledge with GNU/Linux systems; applications such as the bash shell and derivatives; as well as standard tools such as grep, patch, diff, and so on. The examples have been tested with an Ubuntu 14.04 LTS system, but any Linux distribution supported by the Yocto Project can be used.
This is not meant to be an introductory book to the Yocto project, and reading an introductory book, such as Embedded Linux Development with Yocto Project by Otavio Salvador and Daiane Angolini, also from Packt Publishing, is recommended.
This book is structured to follow the usual development workflow of an embedded Linux product, but chapters or even single recipes can be read independently.
The recipes take a practical hands-on approach using a Freescale i.MX6-based system, the wandboard-quad, as base hardware. However, any other piece of i.MX-based hardware can be used to follow the examples.
This book is the ideal way for embedded developers learning about embedded Linux and the Yocto Project to become proficient and broaden their knowledge with examples that are immediately applicable to embedded developments.
Experienced embedded Yocto developers will find new insights into working methodologies and ARM-specific development competence.
In this book, you will find several headings that appear frequently (Getting ready, How to do it, How it works, There's more, and See also).
To give clear instructions on how to complete a recipe, we use these sections:
This section tells you what to expect in the recipe, and describes how to set up any software or any preliminary settings required for the recipe.
This section usually consists of a detailed explanation of what happened in the previous section.
This section consists of additional information about the recipe in order to make you more knowledgeable about the recipe.
In this book, you will find a number of text styles that distinguish between different kinds of information. Here are some examples of these styles and an explanation of their meaning.
Code words in text, database table names, folder names, filenames, file extensions, pathnames, dummy URLs, user input, and Twitter handles are shown as follows: "You can add a list of packages to exclude from cleaning by adding them to the RM_WORK_EXCLUDE variable."
A block of code is set as follows:
SRC_URI = "file://helloworld.c"
S = "${WORKDIR}"When we wish to draw your attention to a particular part of a code block, the relevant lines or items are set in bold:
SRC_URI = "file://helloworld.c"
DEPENDS = "lttng-ust"
S = "${WORKDIR}"Any command-line input or output is written as follows:
$ ls sources/meta-fsl*/conf/machine/*.conf
New terms and important words are shown in bold. Words that you see on the screen, for example, in menus or dialog boxes, appear in the text like this: "Build the project by navigating to Project | Build Project."
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