Slides from January 19, 2017 webinar, An Introduction to the Yocto Embedded Framework.

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An Introduction to the
Yocto Embedded
Framework
Jeff Tranter <jtranter@ics.com>
Integrated Computer Solutions, Inc.

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Agenda
• What is Yocto?
• Why is it Needed?
• What Yocto Provides
• Benefits/Advantages
• Limitations/Disadvantages
• Yocto Versions
• Other Framework Options
• Yocto Architecture
• Major Components
• Using Yocto - Basic Steps
• OpenEmbeddedBuild System
• Bitbake Metadata
• Example - Emulator
• Example - Beaglebone Black
• Building an SDK
• Packaging
• Toaster GUI
• Qt Yocto Support
• Doing More
• Tips For Getting Started
• References
• Summary
• Q&A

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What is Yocto?
• Project to provide templates, tools and methods to create custom
Linux-based embedded systems
• Founded in 2010
• Open Source, managed by The Linux Foundation
• Vendor and platform neutral
• Collaborative effort among participants
• Members/participants/sponsors include Intel, AMD, Broadcom, TI,
Freescale, LG Electronics, Huawei, Mentor Graphics, Dell, The Qt
Company

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Why Is It Needed?
• Embedded development is significantly harder than
native/desktop development
• Cross-compilation
• Wide scope: boot loader, kernel, BSP/device drivers, packaging
format, utilities, applications, SDK
• Large, time consuming to build
• Desire for repeatability, automation
• Licensing issues
• Regular need for security and other updates

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What Yocto Provides
• Framework for creating embedded Linux systems
• Targets supported: ARM, PPC, MIPS, x86, x86-64
• Hosted on common Linux x86 desktop platforms (CentOS, Fedora,
openSUSE, Ubuntu)
• OpenEmbedded build system with bitbake build engine
• IDE
• Graphical interface to build system

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Benefits/Advantages
• Reduced development effort/time
• Improved quality
• Automation
• Stability
• Repeatability

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Limitations/Disadvantages
• Embedded Linux targets only
• Development tools run on desktop Linux only (or in a Linux vm
hosted on e.g. Windows or MacOS)
• Doesn't dictate a specific Linux distribution (but offers Poky as a
reference distribution)
• Large, complex, can have steep learning curve

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Yocto Versions/Code Names

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Other Embedded Frameworks
• Baserock
• Buildroot
• Crosstool/CrosstoolNG
• Embedded Debian/Fedora/Gentoo/SUSE/Ubuntu

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Yocto Architecture

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Major Components
• bitbake
• Poky Linux distribution
• Emulator
• Toaster GUI
• SDK
• Eclipse IDE plugin
• Build Appliance

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Using Yocto - Basic Steps
1. Set up tools on a Linux host machine.
2. Configure bitbake for embedded hardware.
3. Build software components, bootloader, root fs, image.
4. Write boot image and file system.
5. Set up SDK.
6. Develop and iterate.

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bitbake Build System
Steps:
• fetch
• extract
• patch
• configure
• build
• install
• package

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Bitbake Metadata

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Example - Building For Emulator
$ sudo apt-get install gawk wget git-core diffstat unzip
texinfo gcc-multilib build-essential chrpath socat libsdl1.2-
dev xterm

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Example - Building For Emulator
$ mkdir yocto
$ cd yocto
$ wget
http://downloads.yoctoproject.org/releases/yocto/yocto-
2.2/poky-morty-16.0.0.tar.bz2
$ tar xjvf poky-morty-16.0.0.tar.bz2
$ cd poky-morty-16.0.0
$ source oe-init-build-env
$ edit conf/local.conf
$ bitbake core-image-sato
$ runqemu qemuarm

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Example - Building for Beaglebone
Black

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Example - Building for Beaglebone
Black
Device Boot Start End Blocks Id System
/dev/mmcblk0p1 * 2048 146570 72261+ c W95 FAT32(LBA)
/dev/mmcblk0p2 146571 8535178 4194304 83 Linux
$ sudo mkfs.vfat -F 16 -n "boot" /dev/mmcblk0p1
$ sudo mke2fs -j -L "root" /dev/mmcblk0p2

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Example - Building for Beaglebone
Black
$ cp tmp/deploy/images/beaglebone/MLO-beaglebone /media/
$LOGNAME/boot/MLO
$ cp tmp/deploy/images/beaglebone/u-boot-beaglebone.img /media/
$LOGNAME/boot/u-boot.img
$ sudo tar x -C /media/$LOGNAME/root -f
tmp/deploy/images/beaglebone/core-image-sato-beaglebone.tar.bz2

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Building an SDK
$ bitbake core-image-sato -c populate_sdk
Output is:
tmp/deploy/sdk/poky-glibc-x86_64-core-image-sato-armv5e-
toolchain-2.2.sh

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Building an SDK
$ ~/yocto/poky-morty-16.0.0/build/tmp/deploy/sdk/poky-glibc-x86_64-
core-image-sato-armv5e-toolchain-2.2.sh
Poky (Yocto Project Reference Distro) SDK installer version 2.2
===============================================================
Enter target directory for SDK (default: /opt/poky/2.2): ~/sdk
You are about to install the SDK to "/home/tranter/sdk". Proceed[Y/n]? Y
Extracting
SDK......................................................................do
ne
Setting it up...done
SDK has been successfully set up and is ready to be used.
Each time you wish to use the SDK in a new shell session, you need to
source the environment setup script e.g.
$ . /home/tranter/sdk/environment-setup-armv5e-poky-linux-gnueabi

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Building an SDK
$ . /home/tranter/sdk/environment-setup-armv5e-poky-linux-gnueabi
$ echo $CXX
arm-poky-linux-gnueabi-g++ -march=armv5e -marm
--sysroot=/home/tranter/sdk/sysroots/armv5e-poky-linux-gnueabi
$ $CXX helloworld.cpp
$ file a.out
a.out: ELF 32-bit LSB executable, ARM, EABI5 version 1 (SYSV),
dynamically linked, interpreter /lib/ld-linux.so.3, for GNU/Linux
3.2.0

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Packaging
• Not required, but often useful even for embedded systems.
• Yocto doesn't impose a packaging format.
• Common package formats include:
• rpm
• deb/dpkg
• ipkg
• opkg

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Toaster GUI

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Yocto Qt Support
Yocto Qt 5 recipes:
• https://github.com/meta-qt5/meta-qt5
Qt for Device Creation (boot2qt):
• http://code.qt.io/cgit/yocto/meta-boot2qt.git/
• http://code.qt.io/cgit/yocto/meta-qt5.git/

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More About Bitbake
• Python based language for configuration files.
• Supports variables, include files, functions, inheritance.
• Uses scripts called "recipes".
• Many command line options.
• Configuration files in build/conf
• Understands dependencies.
• Multithreaded, runs a server process in the background.

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Doing More - Writing Recipes
• Needed to build your own components with bitbake
• Shell or Python scripts (.bb files)
• Standardized format

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Doing More - Kernel Recipes
• Recipes to configure, patch, and build the Linux kernel
• More complex

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Doing More - BSPs
• BSP = Board Support Package.
• Adaptations for specific hardware.
• Hardware vendor, OS vendor, or third party may provide this.

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Doing More - Eclipse Integration

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Doing More - Licensing and
Compliance

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Tips For Getting Started

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References
1. Embedded Linux Systems with the Yocto Project, Rudolf Streif
2. https://www.yoctoproject.org/
3. https://github.com/meta-qt5/meta-qt5
4. http://code.qt.io/cgit/yocto/meta-boot2qt.git/
5. http://code.qt.io/cgit/yocto/meta-qt5.git/
6. http://www.ics.com/blog/yocto-quick-start

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Summary

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Questions?

36. © Integrated Computer Solutions, Inc. All Rights Reserved
An Introduction to the
Yocto Embedded
Framework
Jeff Tranter <jtranter@ics.com>
Integrated Computer Solutions, Inc.