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Embedded Linux Development using Yocto Projects

By : Otavio Salvador, Angolini

3.4 (5)

Embedded Linux Development using Yocto Projects

3.4 (5)

By: Otavio Salvador, Angolini

Overview of this book

Yocto Project is turning out to be the best integration framework for creating reliable embedded Linux projects. It has the edge over other frameworks because of its features such as less development time and improved reliability and robustness. Embedded Linux Development using Yocto Project starts with an in-depth explanation of all Yocto Project tools, to help you perform different Linux-based tasks. The book then moves on to in-depth explanations of Poky and BitBake. It also includes some practical use cases for building a Linux subsystem project using Yocto Project tools available for embedded Linux. The book also covers topics such as SDK, recipetool, and others. By the end of the book, you will have learned how to generate and run an image for real hardware boards and will have gained hands-on experience at building efficient Linux systems using Yocto Project.

Preface

Preface

What this book covers

What you need for this book

Who this book is for

Conventions

Customer support

Free Chapter

Meeting the Yocto Project

Meeting the Yocto Project

What is the Yocto Project?

Delineating the Yocto Project

Understanding Poky

Using BitBake

OpenEmbedded-Core

Metadata

The alliance of the OpenEmbedded Project and the Yocto Project

Summary

Baking Our Poky-Based System

Baking Our Poky-Based System

Configuring a host system

Downloading the Poky source code

Preparing the build environment

Knowing the local.conf file

Building a target image

Running images in QEMU

Summary

Using Toaster to Bake an Image

Using Toaster to Bake an Image

What is Toaster?

Installing Toaster

Starting Toaster

Building an image to QEMU

Summary

Grasping the BitBake Tool

Grasping the BitBake Tool

Understanding the BitBake tool

Exploring metadata

Parsing metadata

Dependencies

Preferring and providing recipes

Fetching the source code

Understanding BitBake's tasks

Generating a root filesystem image

Summary

Detailing the Temporary Build Directory

Detailing the Temporary Build Directory

Detailing the build directory

Constructing the build directory

Exploring the temporary build directory

Understanding the work directory

Understanding the sysroot directories

Summary

Assimilating Packaging Support

Assimilating Packaging Support

Using supported package formats

Understanding shared state cache

Explaining package versioning

Specifying runtime package dependencies

Package feeds

Summary

Diving into BitBake Metadata

Diving into BitBake Metadata

Using metadata

Summary

Developing with the Yocto Project

Developing with the Yocto Project

Deciphering the software development kit

Working with the Poky SDK

Integrating with Eclipse

Summary

Debugging with the Yocto Project

Debugging with the Yocto Project

Differentiating metadata and application debugging

Tracking image, package, and SDK contents

Debugging packaging

Logging information during task execution

Utilizing a development shell

Using the GNU Project Debugger for debugging

Summary

Exploring External Layers

Exploring External Layers

Powering flexibility with layers

Detailing the layer's source code

Adding meta layers

The Yocto Project layer ecosystem

Summary

Creating Custom Layers

Creating Custom Layers

Making a new layer

Adding metadata to the layer

Creating an image

Adding a package recipe

Adding support to a new machine definition

Using a custom distribution

MACHINE_FEATURES versus DISTRO_FEATURES

Understanding the variables scope

Summary

Customizing Existing Recipes

Customizing Existing Recipes

Common use cases

Adding extra options to recipes based on Autoconf

Applying a patch

Adding extra files to the existing packages

Changing recipe feature configuration

Customizing BusyBox

Customizing the linux-yocto framework

Summary

Achieving GPL Compliance

Achieving GPL Compliance

Understanding copyleft

Managing software licensing with Poky

Using Poky to achieve copyleft compliance

Summary

Booting Our Custom Embedded Linux

Booting Our Custom Embedded Linux

Exploring the boards

Discovering the right BSP layer

Baking for the hardware

Booting our baked image

Next steps

Summary

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Changing recipe feature configuration

One supported mechanism to simplify feature set customization for recipes is PACKAGECONFIG. It provides a way to enable and disable the recipe features. For example, say the recipe has the following configuration:

PACKAGECONFIG ?= "feature1"
PACKAGECONFIG[feature1] = "--enable-feature1,--disablefeature1, feature1depends"
PACKAGECONFIG[feature2] = "--enable-feature2,--disablefeature2, feature2depends"

The recipe has two features, feature1 and feature2. For each configuration option, there is a string to define how to enable the feature on autoconf, how to disable the feature on autoconf, and the new dependencies in case the option is enabled.

We can create a .bbappend file that expands the PACKAGECONFIG variable's default value to enable feature2 as well, as shown here:

PACKAGECONFIG += "feature2"

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