Book Image

Embedded Linux Development using Yocto Projects - Second Edition

By : Otavio Salvador, Daiane Angolini
Book Image

Embedded Linux Development using Yocto Projects - Second Edition

By: Otavio Salvador, Daiane 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.

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Table of Contents (22 chapters)
Title Page
Title Page
Credits
Credits
About the Authors
About the Authors
About the Reviewer
About the Reviewer
www.PacktPub.com
www.PacktPub.com
Customer Feedback
Customer Feedback
Preface
Preface
Free Chapter
1
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
2
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
3
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
4
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
5
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
6
Assimilating Packaging Support
Assimilating Packaging Support
Using supported package formats
Understanding shared state cache
Explaining package versioning
Specifying runtime package dependencies
Package feeds
Summary
7
Diving into BitBake Metadata
Diving into BitBake Metadata
Using metadata
Summary
8
Developing with the Yocto Project
Developing with the Yocto Project
Deciphering the software development kit
Working with the Poky SDK
Integrating with Eclipse
Summary
9
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
10
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
11
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
12
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
13
Achieving GPL Compliance
Achieving GPL Compliance
Understanding copyleft
Managing software licensing with Poky
Using Poky to achieve copyleft compliance
Summary
14
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
Index
Index

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"

Note

In order to add the same feature to the build/conf/local.conf file, we can use PACKAGECONFIG_pn-<recipename>_append = 'feature2'.

More detailed information...

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