Yocto with raspberry pi

The Yocto Project (YP) is an open source collaboration project that helps developers create custom Linux-based systems regardless of the hardware architecture. The project provides a flexible set of tools and a space where embedded developers worldwide can share technologies, software stacks, configurations, and best practices that can be used to create tailored Linux images for embedded and IOT devices, or anywhere a customized Linux OS is needed.

For more info visit yoctoproject

The build process

Below steps cover the environment setup and process to build yocto from the source tree for Raspberry Pi board.

Build Environment Setup

Install the following package

 sudo apt-get update
 sudo apt-get install gawk wget git-core diffstat unzip texinfo gcc-multilib build-essential chrpath socat libsdl12-dev xterm liblz4-tool python

Clone Yocto: kirkstone branch

Clone yocto git repo using below command

 cd ~
 mkdir yocto
 cd yocto

 git clone -b kirkstone git://git.yoctoproject.org/poky

 cd poky

 git checkout remotes/origin/kirkstone

 cd ~/yocto/
 git clone -b kirkstone git://git.yoctoproject.org/meta-raspberrypi

 source oe-init-build-env

Clone custom repo

 cd ~/yocto
 git clone https://gitlab.com/vishalkuma/yocto-rpi.git
 
 cd yocto-rpi
 git switch develop

 mv meta-rpilinux  meta-vishal ~/yocto/

 cd ~/yocto

 rm -rf yocto-rpi

Editing bblayers.conf

The bblayers.conf file defines layers, which are directory trees, traversed (or walked) by BitBake. The bblayers.conf file uses the BBLAYERS variable to list the layers BitBake tries to find. for more info, visit info

By default the bblayers.conf file in ~/yocto/poky/build/conf/ should look like

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

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

 BBLAYERS ?= " \
   /home/vishal/yocto/poky/meta \
   /home/vishal/yocto/poky/meta-poky \
   /home/vishal/yocto/poky/meta-yocto-bsp \
   "

Add meta-raspberrypi meta-rpilinux and meta-vishal to bblayers.conf. now bblayers.conf file should look like

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

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

 BBLAYERS ?= " \
   /home/vishal/yocto/poky/meta \
   /home/vishal/yocto/poky/meta-poky \
   /home/vishal/yocto/poky/meta-yocto-bsp \
   /home/vishal/yocto/meta-raspberrypi \
   /home/vishal/yocto/meta-rpilinux \
   /home/vishal/yocto/meta-vishal \
   "

Editing local.conf

This configuration file contains all the local user configurations for your build environment. The local.conf file contains documentation on the various configuration options. for more info, visit info

local.conf file will be in ~/yocto/poky/build/conf/

Add target machine for the build, Look for the MACHINE ??= "qemux86-64" line in the file and change it to:

 MACHINE ??= "raspberrypi3-64"

The raspberrypi3-64 is pointing to an configuration file raspberrypi3-64.conf (for raspberry pi-3 64-bit) located at meta-raspberrypi/conf/machine/raspberrypi3-64.conf

Add image target to conf-notes.txt

By default yocto uses some common target, Here we have own custom targed image (named rpilinux-image) created in ~/yocto/meta-rpilinux/recipes-rpilinux/images/rpilinux-image.bb so it will be better for user prospective to add this image to config notes. conf-notes.txt located inside ~/yocto/poky/meta-poky/conf/

 
 ### Shell environment set up for builds. ###

 You can now run 'bitbake <target>'

 Common targets are:
    core-image-minimal
    core-image-full-cmdline
    core-image-sato
    core-image-weston
    meta-toolchain
    meta-ide-support
    rpilinux-image

 You can also run generated qemu images with a command like 'runqemu qemux86'

 Other commonly useful commands are:
  - 'devtool' and 'recipetool' handle common recipe tasks
  - 'bitbake-layers' handles common layer tasks
  - 'oe-pkgdata-util' handles common target package tasks
 

Build image

 cd ~/Yocto/poky
 source oe-init-build-env
 bitbake rpilinux-image

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