Linux Yocto for Raspberry Pi

Deploy Yocto 2.6 codename “Thud” on Raspberry Pi Zero Wireless

Yocto Project Release	LTSI Kernel Version	LTS Kernel Version	Released Kernel Version
Yocto Project 2.6	linux-yocto_4.9	linux-yocto_4.14	linux-yocto_4.18

---

Clone Yocto Layers

# Create your workspace
$ mkdir my_yocto && cd my_yocto

## Clone Git repos
# The build system
$ git clone -b thud git://git.yoctoproject.org/poky && cd poky

# Specific meta for Raspberry Pi boards
$ git clone -b thud git://git.yoctoproject.org/meta-raspberrypi

---

Setup the environment

# Setup the yocto environnement by sourcing the oe init script
$ . oe-init-build-env ../build

You had no conf/local.conf file. This configuration file has therefore been
created for you with some default values. You may wish to edit it to, for
example, select a different MACHINE (target hardware). See conf/local.conf
for more information as common configuration options are commented.

You had no conf/bblayers.conf file. This configuration file has therefore been
created for you with some default values. To add additional metadata layers
into your configuration please add entries to conf/bblayers.conf.

The Yocto Project has extensive documentation about OE including a reference
manual which can be found at:
    http://yoctoproject.org/documentation

For more information about OpenEmbedded see their website:
    http://www.openembedded.org/

### Shell environment set up for builds. ###
You can now run 'bitbake <target>'

Common targets are:
    core-image-minimal
    core-image-sato
    meta-toolchain
    meta-ide-support

---

Add specific Meta

Before going further, the meta “Raspberry Pi” has to be declared into the build system of Yocto. Indeed, additional metas are not recognized automatically. To do so, edit the conf/bblayers file as the following.

$ vim build/conf/bblayers.conf

# POKY_BBLAYERS_CONF_VERSION is increased each time build/conf/bblayers.conf
# changes incompatibly
POKY_BBLAYERS_CONF_VERSION = "2"

BBPATH = "${TOPDIR}"
BBFILES ?= ""

BBLAYERS ?= " \
  /home/wp_user/workspace/my_yocto/poky/meta \
  /home/wp_user/workspace/my_yocto/poky/meta-poky \
  /home/wp_user/workspace/my_yocto/poky/meta-yocto-bsp \
  /home/wp_user/workspace/my_yocto/poky/meta-raspberrypi \
  "

---

Choose the target

Then, the last but most cool Yocto step is to choose the target machine. Raspberry Pi are ashamedly not mentioned among default machine choices because it comes from the meta-raspberrypi, so it must be added manually as showed below. All possible machines are available into “my_yocto/poky/meta-raspberrypi/conf/machine/”

Raspberry Pi machines	Model	SOC version
raspberrypi0	Raspberry Pi Zero v1.3	BCM2835
raspberrypi0-wifi	Raspberry Pi Zero Wireless	BCM2835
raspberrypi2	Raspberry Pi 2 (model B)	BCM2836
raspberrypi3-64	Raspberry Pi 3 64 bits (model B)	BCM2837
raspberrypi3	Raspberry Pi 3 (model B)	BCM2837
raspberrypi-cm3	Raspberry Pi Compute module 3	BCM2837
raspberrypi-cm	Raspberry Pi Compute module 1	BCM2835
raspberrypi	?	?

$ vim build/conf/local.conf

[...]
# This sets the default machine to be qemux86 if no other machine is selected:
#MACHINE ??= "qemux86"
MACHINE ??= "raspberrypi3"
[...]

---

Build a very first image 🙂

# Install build dependencies (ubuntu and debian)
$ sudo apt-get install gawk wget git-core diffstat unzip texinfo gcc-multilib build-essential chrpath socat libsdl1.2-dev xterm

# Launch the build
$ bitbake core-image-base

Parsing recipes: 100% |#########################################################################################################################| Time: 0:03:04
Parsing of 817 .bb files complete (0 cached, 817 parsed). 1290 targets, 68 skipped, 0 masked, 0 errors.
NOTE: Resolving any missing task queue dependencies

Build Configuration:
BB_VERSION           = "1.40.0"
BUILD_SYS            = "x86_64-linux"
NATIVELSBSTRING      = "debian-9"
TARGET_SYS           = "arm-poky-linux-gnueabi"
MACHINE              = "raspberrypi"
DISTRO               = "poky"
DISTRO_VERSION       = "2.6.1"
TUNE_FEATURES        = "arm armv6 vfp arm1176jzfs callconvention-hard"
TARGET_FPU           = "hard"
meta
meta-poky
meta-yocto-bsp       = "thud:cc73390a75d98b96eb861ae0624283c1ea6ef1bd"
meta-raspberrypi     = "thud:a48743dc36e31170cf737e200cc88f273e13611a"

---

Troubleshooting

The first build is very time, memory and power consuming for your host machine !

≈ 50Go

≈ 1h of work

(with 8 cores CPU Intel Xeon 2620 v4 @ 2.1Ghz and 100Mbps internet bandwidth)