Yocto Linux

Summary
Steps
Appendix

Summary

This page lists all the steps to build a Yocto based distro for de10-nano-soc. Yocto is a complete build system i.e. it generates everything needed for a fully functioning Linux system for your DE10-Nano and this includes the bootloader (U-Boot), kernel and the rootFS.

Please Note - The steps listed on this page are from my experiments with Yocto. I've abandoned it in favour of Debian and keeping it here just for reference. The main problem when using Yocto is that the build process takes a very long time (4-5 hours on my virtualbox) and a lot of space (~50-100GB). The rest of the guide assumes that you are using Debian and not Yocto.

Steps

Preparing the sources

Create a working directory:
```
mkdir yocto
```

Get the Yocto sources:

git clone git://git.yoctoproject.org/poky.git

Get the meta-altera recipes for Yocto:

git clone git://github.com/kraj/meta-altera.git

Visit the Yocto releases page and choose which release you wish to use. For this guide, we will choose dunfell as its the latest with long term support. Switch the branch in the poky repository to dunfell
```
cd poky
git checkout dunfell
cd ..
```
Prepare for the configuration and the build:
```
source poky/oe-init-build-env ./build
```
This creates the build folder and cds into it. It also sets various environment variables, config files etc.

Configuration

Now we update the config files for our requirements. The steps followed here are not exhaustive, but they are meant to give a minimum console based Linux distro which can be used for most FPGA-HPS projects. For more information, look into the links in the appendix.

Add the meta-altera recipe to the Yocto build:

vim conf/bblayers.conf

Add the following line which points to the meta-altera recipe to the BBLAYERS variable, one line above the closing quotation mark.

${TOPDIR}/../meta-altera \

So your file should now look like this:

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

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

BBLAYERS ?= " \
  /home/myuser/yocto/poky/meta \
  /home/myuser/yocto/poky/meta-poky \
  /home/myuser/yocto/poky/meta-yocto-bsp \
  ${TOPDIR}/../meta-altera \
  "

Yocto uses conf/local.conf for the vast majority of it's configuration options. We will use the following options for this particular build. Copy paste all these options and paste them at the end of the file:
```
MACHINE = "cyclone5"
PACKAGE_CLASSES = "package_deb"
EXTRA_IMAGE_FEATURES = "debug-tweaks tools-sdk tools-debug package-management"
PREFERRED_PROVIDER_virtual/kernel = "linux-altera"
PREFERRED_VERSION_linux-altera = "5.7%"
UBOOT_CONFIG = "de10-nano-soc"
UBOOT_EXTLINUX_FDT_default = "../soc_system.dtb"
IMAGE_INSTALL_append += " apt dpkg "
PACKAGE_FEED_URIS = "http://mirror.0x.sg/debian/"
PACKAGE_FEED_BASE_PATHS = "rpm"
PACKAGE_FEED_ARCHS = "all armhf"
```
Let's go through these in detail:
1. The de10-Nano uses a cyclone5 chip. So we have to specify that as the machine:
```
MACHINE = "cyclone5"
```
2. We want this to be a debian based distro. So we want to use the deb package classes:
```
PACKAGE_CLASSES = "package_deb"
```
3. tools-sdk and tools-debug are necessary to have gcc and make and other build essential utilities available. We're also including package-management because we want it to have a package manager.
```
EXTRA_IMAGE_FEATURES = "debug-tweaks tools-sdk tools-debug package-management"
```
4. Use the linux-altera configuration for the kernel.
```
PREFERRED_PROVIDER_virtual/kernel = "linux-altera"
```
5. Which version of the kernel to use? Assuming you are in the build directory, the following command lists all the available kernel options to use:
```
ls ../meta-altera/recipes-kernel/linux/
```
  In our case, we want to use 5.7, so we use the following:
```
PREFERRED_VERSION_linux-altera = "5.7%"
```
6. TODO: Explain the remaining parameters in the config.