Book Image

Embedded Linux Development Using Yocto Project - Third Edition

By : Otavio Salvador, Daiane Angolini
Book Image

Embedded Linux Development Using Yocto Project - Third Edition

By: Otavio Salvador, Daiane Angolini

Overview of this book

The Yocto Project is the industry standard for developing dependable embedded Linux projects. It stands out from other frameworks by offering time-efficient development with enhanced reliability and robustness. With Embedded Linux Development Using Yocto Project, you’ll acquire an understanding of Yocto Project tools, helping you perform different Linux-based tasks. You’ll gain a deep understanding of Poky and BitBake, explore practical use cases for building a Linux subsystem project, employ Yocto Project tools available for embedded Linux, and uncover the secrets of SDK, recipe tool, and others. This new edition is aligned with the latest long-term support release of the aforementioned technologies and introduces two new chapters, covering optimal emulation in QEMU for faster product development and best practices. By the end of this book, you’ll be well-equipped to generate and run an image for real hardware boards. You’ll gain hands-on experience in building efficient Linux systems using the Yocto Project.

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Table of Contents (20 chapters)
Preface
Preface
Who this book is for
What this book covers
To get the most out of this book
Download the color images
Conventions used
Get in touch
Share Your Thoughts
Download a free PDF copy of this book
1
Chapter 1: Meeting the Yocto Project
Chapter 1: Meeting the Yocto Project
What is the Yocto Project?
Delineating the Yocto Project
The alliance of the OpenEmbedded project and the Yocto Project
Understanding Poky
The Yocto Project releases
Summary
Free Chapter
2
Chapter 2: Baking Our First Poky-Based System
Chapter 2: Baking Our First Poky-Based System
Preparing the build 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
Chapter 3: Using Toaster to Bake an Image
Chapter 3: Using Toaster to Bake an Image
What is Toaster?
Installing Toaster
Starting Toaster
Building an image for QEMU
Summary
4
Chapter 4: Meeting the BitBake Tool
Chapter 4: Meeting the BitBake Tool
Understanding the BitBake tool
BitBake metadata collections
Metadata types
Summary
5
Chapter 5: Grasping the BitBake Tool
Chapter 5: Grasping the BitBake Tool
Parsing metadata
Dependencies
Preferring and providing recipes
Fetching the source code
Optimizing the source code download
Understanding BitBake’s tasks
Summary
6
Chapter 6: Detailing the Temporary Build Directory
Chapter 6: 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
7
Chapter 7: Assimilating Packaging Support
Chapter 7: Assimilating Packaging Support
Using supported package formats
Running code during package installation
Understanding shared state cache
Explaining package versioning
Specifying runtime package dependencies
Using packages to generate a rootfs image
Package feeds
Summary
8
Chapter 8: Diving into BitBake Metadata
Chapter 8: Diving into BitBake Metadata
Understanding BitBake’s metadata
Summary
9
Chapter 9: Developing with the Yocto Project
Chapter 9: Developing with the Yocto Project
What is a software development kit?
Generating a native SDK for on-device development
Understanding the types of cross-development SDKs
Using the Standard SDK
Using the Extensible SDK
Summary
10
Chapter 10: Debugging with the Yocto Project
Chapter 10: Debugging with the Yocto Project
Differentiating metadata and application debugging
Tracking image, package, and SDK contents
Debugging packaging
Logging information during task execution
Debugging metadata variables
Utilizing a development shell
Using the GNU Debugger for debugging
Summary
11
Chapter 11: Exploring External Layers
Chapter 11: Exploring External Layers
Powering flexibility with layers
Detailing a layer’s source code
Adding meta layers
The Yocto Project layer ecosystem
Summary
12
Chapter 12: Creating Custom Layers
Chapter 12: Creating Custom Layers
Making a new layer
Adding metadata to the layer
MACHINE_FEATURES versus DISTRO_FEATURES
Understanding the scope of a variable
Summary
13
Chapter 13: Customizing Existing Recipes
Chapter 13: Customizing Existing Recipes
Understanding common use cases
Adding extra options to recipes based on Autotools
Applying a patch
Adding extra files to the existing packages
Configuration fragments for Kconfig-based projects
Summary
14
Chapter 14: Achieving GPL Compliance
Chapter 14: Achieving GPL Compliance
Understanding copyleft
Managing software licensing with Poky
Using Poky to achieve copyleft compliance
Summary
15
Chapter 15: Booting Our Custom Embedded Linux
Chapter 15: Booting Our Custom Embedded Linux
Discovering the right BSP layer
Using physical hardware
BeagleBone Black
Raspberry Pi 4
VisionFive
Taking the next steps
Summary
16
Chapter 16: Speeding Up Product Development through Emulation – QEMU
Chapter 16: Speeding Up Product Development through Emulation – QEMU
What is QEMU?
What are the benefits of using QEMU over hardware?
When is choosing real hardware preferable?
Using runqemu capabilities
Summary
17
Chapter 17: Best Practices
Chapter 17: Best Practices
Guidelines to follow for Yocto Project
Guidelines to follow for general projects
Summary
18
Index
Index
Why subscribe?
19
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Explaining package versioning

Package versioning is used to differentiate the same package in distinct stages of its life cycle. From Poky’s perspective, it is also used as part of the equation that generates the checksum used by BitBake to verify whether a task must be rebuilt.

The package version, also known as PV, plays a leading role when we select which recipe to build. The default behavior of Poky is always to prefer the newest recipe version unless there is a different explicit preference, as discussed in Chapter 5, Grasping the BitBake Tool. For example, let’s suppose that we have two versions of the myrecipe recipe:

  • myrecipe_1.0.bb
  • myrecipe_1.1.bb

BitBake, by default, builds the recipe with version 1.1. Inside the recipe, we may have other variables that compose package versioning with the PV variable. These are the package epoch, known as PE, and the package revision, known as PR.

Those variables normally follow this pattern:

...
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