Creating a Custom Xilinx Yocto Layer

Table of Contents

Introduction

This wiki shows how to create a custom layer in an open source Xilinx Yocto flow.  After creating the layer, it provides an example of creating your own machine based on a ZCU102 configuration.

Releases Supported

Xilinx Yocto rel-v2018.1 and later (Rocko 2.4)

Prerequisites

Yocto Supported Linux Distro

Xilinx Tools Dependencies (not required for rel-v2018.3 and later)

Xilinx Open Source Yocto Installation

Xilinx Tools Path

Don't forget to edit the path and version variables in local.conf to point to the current SDK root directory.

Creating Your Custom Layer

You may create your custom layer manually by copying an existing layer.conf, however, Yocto provides some helper scripts to automate it.  The bitbake-layers create-layer script will generate a base layer with a default priority of 6.  Once the layer is created, you can either add the layer to bblayers.conf manually or use the bitbake-layers add-layer to automate it.  Note that adding it manually will be faster, but may increase the likelihood of typos or syntax errors.  The sequence below is an example of how to apply these scripts.  You may cut-and-paste the commands below into a local script to further automate this flow.  The resulting layer.conf and bblayers.conf are shown below.

Create Yocto Layer
export LAYER=example # your layer name goes here
# From Yocto root directory
source setupsdk
# Optional: Make a backup copy of local.conf and bblayers.conf
cp conf/local.conf conf/local.conf.bk
cp conf/bblayers.conf conf/bblayers.conf.bk
# Add a default MACHINE in local.conf or specify on the command line for bitbake, e.g. MACHINE=zcu102-zynqmp
echo 'MACHINE ?= "zcu102-zynqmp"' >> conf/local.conf
# Create your layer in the sources directory
cd ../sources
bitbake-layers create-layer meta-$LAYER
# Create custom layer directory structure for Xilinx components
cd meta-$LAYER
mkdir -p conf/machine recipes-kernel/linux-xlnx recipes-bsp/u-boot/u-boot-xlnx recipes-bsp/device-tree/files \
recipes-bsp/hdf/files recipes-bsp/fsbl/files recipes-bsp/pmu-firmware/files
# Add new layer with bitbake-layers or edit bblayers.conf manually
cd ../../build
bitbake-layers add-layer ../sources/meta-$LAYER

layer.conf

In releases rel-v2018.1 and rel-v2018.2, edit conf/layer.conf.  If there is a double backward slash “\\” in the BBFILES variable, delete one backward slash, so there is only a single backward slash “\”.  This is required for proper line continuation, otherwise your bbappend files will not be found.

layer.conf
# We have a conf and classes directory, add to BBPATH
BBPATH .= ":${LAYERDIR}"

# We have recipes-* directories, add to BBFILES
BBFILES += "${LAYERDIR}/recipes-*/*/*.bb \
            ${LAYERDIR}/recipes-*/*/*.bbappend"

BBFILE_COLLECTIONS += "meta-example"
BBFILE_PATTERN_meta-example = "^${LAYERDIR}/"
BBFILE_PRIORITY_meta-example = "6"
bblayers.conf
LCONF_VERSION = "7"

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

BBLAYERS ?= " \
  /home/emil/yocto/sources/core/meta \
  /home/emil/yocto/sources/core/meta-poky \
<...>
  /home/emil/yocto/sources/core/../meta-xilinx/meta-xilinx-bsp \
  /home/emil/yocto/sources/core/../meta-xilinx/meta-xilinx-contrib \
  /home/emil/yocto/sources/core/../meta-xilinx-tools \
  /home/emil/yocto/sources/core/../meta-petalinux \
  /home/emil/yocto/sources/core/../meta-virtualization \
  /home/emil/yocto/sources/core/../meta-openamp \
  /home/emil/yocto/sources/meta-example \
  "

BBLAYERS_NON_REMOVABLE ?= " \
    /home/emil/yocto/sources/core/meta \
"

Custom Layer Directory Structure

After the directory structure is created, you can begin populating the layer with recipes, bbappends, patches, cfg fragments, machine configs, etc.  The example.bb recipe is an artifact of the create-layer and can be safely deleted.  You can continue expanding your layer to include recipes for custom BSPs, applications and other open source components or stacks.  At this point, it's pretty straight forward to put your layer under Git control.

meta-example
$ tree meta-example
meta-example
├── conf
│   ├── layer.conf
│   └── machine
├── COPYING.MIT
├── README
├── recipes-bsp
│   ├── device-tree
│   │   └── files
│   ├── fsbl
│   │   └── files
│   ├── hdf
│   │   └── files
│   ├── pmu-firmware
│   │   └── files
│   └── u-boot
│       └── u-boot-xlnx
├── recipes-example
│   └── example
│       └── example.bb
└── recipes-kernel
    └── linux-xlnx

Verify Your Layer

You can verify that your custom layer has been properly added to the Yocto build system by running bitbake-layers show-layers as shown below.

show-layers
$ bitbake-layers show-layers | grep meta-example
meta-example          /home/emil/yocto/sources/meta-example  6

Removing Your Layer

To remove a layer, you can either manually edit the bblayers.conf or use the bitbake-layers remove-layer script as shown below from the build directory.

remove-layer
$ bitbake-layers remove-layer meta-example

Creating a New Machine Configuration

Now lets create a machine configuration that inherits all of the defaults from the zcu102-zynqmp machine.  The name of this new machine will be the tuple example-zcu102-zynqmp.  In the conf/machine directory of your custom layer, create a machine configuration file named example-zcu102-zynqmp.conf with the require statement below .  This will include all of the defaults from the zcu102-zynqmp.  At this point you can customize the machine by adding new properties or overriding any of the zcu102-zynqmp defaults.

conf/machine/example-zcu102-zynqmp.conf
require conf/machine/zcu102-zynqmp.conf

Now you can build your new machine by specifying the MACHINE variable on the bitbake command line.

bitbake
$ MACHINE=example-zcu102-zynqmp bitbake petalinux-image-minimal

baking

Make sure you have sourced setupsdk and you are in the build directory when baking.

Adding an HDF to a Xilinx Yocto Layer

Customizing Device Trees in Xilinx Yocto

Xilinx Yocto Builds without an Internet Connection

References

Yocto Project Mega-Manual (2.4.4)