Document Purpose: How to add a new system to the OpenBMC distribution
Audience: Programmer familiar with OpenBMC
Prerequisites: Completed Development Environment Setup Document
This document will describe the following:
The OpenBMC distribution is based on Yocto. Yocto is a project that allows developers to create custom Linux distributions. OpenBMC uses Yocto to create their embedded Linux distribution to run on a variety of devices.
Yocto has a concept of hierarchical layers. When you build a Yocto-based distribution, you define a set of layers for that distribution. OpenBMC uses many common layers from Yocto as well as some of its own layers. The layers defined within OpenBMC can be found with the meta-* directories in OpenBMC GitHub.
Yocto layers are a combination of different files that define packages to incorporate in that layer. One of the key file types used in these layers is BitBake recipes.
BitBake is a fully functional language in itself. For this lesson, we will focus on only the aspects of BitBake required to understand the process of adding a new system.
For this work, you will need to have allocated at least 100GB of space to your development environment and as much memory and CPU as possible. The initial build of an OpenBMC distribution can take hours. Once that first build is done though, future builds will use cached data from the first build, speeding the process up by orders of magnitude.
So before we do anything else, let's get that first build going.
Follow the direction on the OpenBMC GitHub page for the Romulus system (steps 2-4).
While the BitBake operation is going above, let's start creating our new system. Similar to previous lessons, we'll be using Romulus as our reference. Our new system will be called romulus-prime.
From your openbmc repository you cloned above, the Romulus layer is defined within meta-ibm/meta-romulus/. The Romulus layer is defined within the conf subdirectory. Under conf you will see a layout like this:
meta-ibm/meta-romulus/conf/
├── bblayers.conf.sample
├── conf-notes.txt
├── layer.conf
├── local.conf.sample
└── machine
└── romulus.conf
To create our new romulus-prime system we are going to start out by copying our romulus layer.
cp -R meta-ibm/meta-romulus meta-ibm/meta-romulus-prime
Let's review and modify each file needed in our new layer
meta-ibm/meta-romulus-prime/conf/bblayers.conf.sample
This file defines the layers to pull into the meta-romulus-prime distribution. You can see in it a variety of Yocto layers (meta, meta-poky, meta-openembedded/meta-oe, ...). It also has OpenBMC layers like meta-phosphor, meta-openpower, meta-ibm, and meta-ibm/meta-romulus.
The only change you need in this file is to change the two instances of meta-romulus to meta-romulus-prime. This will ensure your new layer is used when building your new system.
meta-ibm/meta-romulus-prime/conf/conf-notes.txt
This file simply states the default target the user will build when working with your new layer. This remains the same as it is common for all OpenBMC systems.
meta-ibm/meta-romulus-prime/conf/layer.conf
The main purpose of this file is to tell BitBake where to look for recipes (*.bb files). Recipe files end with a .bb extension and are what contain all of the packaging logic for the different layers. .bbappend files are also recipe files but provide a way to append onto .bb files. .bbappend files are commonly used to add or remove something from a corresponding .bb file in a different layer.
The only change you need in here is to find/replace the "romulus-layer" to "romulus-prime-layer"
meta-ibm/meta-romulus-prime/conf/local.conf.sample
This file is where all local configuration settings go for your layer. The documentation in it is well done and it's worth a read.
The only change required in here is to change the MACHINE to romulus-prime.
meta-ibm/meta-romulus-prime/conf/machine/romulus.conf
This file describes the specifics for your machine. You define the kernel device tree to use, any overrides to specific features you will be pulling in, and other system specific pointers. This file is a good reference for the different things you need to change when creating a new system (kernel device tree, MRW, LED settings, inventory access, ...)
The first thing you need to do is rename the file to romulus-prime.conf.
Note If our new system really was just a variant of Romulus, with the same hardware configuration, then we could have just created a new machine in the Romulus layer. Any customizations for that system could be included in the corresponding .conf file for that new machine. For the purposes of this exercise we are assuming our romulus-prime system has at least a few hardware changes requiring us to create this new layer.
This will not initially compile but it's good to verify a few things from the initial setup are done correctly.
Do not start this step until the build we started at the beginning of this lesson has completed.
Modify the conf for your current build
Within the shell you did the initial "bitbake" operation you need to reset the conf file for your build. You can manually copy in the new files or just remove it and let BitBake do it for you:
cd .. rm -r ./build/conf export TEMPLATECONF=meta-ibm/meta-romulus-prime/conf . openbmc-env
Run your "bitbake" command.
Nothing RPROVIDES 'romulus-prime-config'
This will be your first error after running "bitbake obmc-phosphor-image" against your new system.
The openbmc/skeleton repository was used for initial prototyping of OpenBMC. Within this repository is a configs directory.
The majority of this config data is no longer used but until it is all completely removed, you need to provide it.
Since this repository and file are on there way out, we'll simply do a quick workaround for this issue.
Create a config files as follows:
cp meta-ibm/meta-romulus-prime/recipes-phosphor/workbook/romulus-config.bb meta-ibm/meta-romulus-prime/recipes-phosphor/workbook/romulus-prime-config.bb
vi meta-ibm/meta-romulus-prime/recipes-phosphor/workbook/romulus-prime-config.bb
SUMMARY = "Romulus board wiring"
DESCRIPTION = "Board wiring information for the Romulus OpenPOWER system."
PR = "r1"
inherit config-in-skeleton
#Use Romulus config
do_make_setup() {
cp ${S}/Romulus.py \
${S}/obmc_system_config.py
cat <<EOF > ${S}/setup.py
from distutils.core import setup
setup(name='${BPN}',
version='${PR}',
py_modules=['obmc_system_config'],
)
EOF
}
Re-run your "bitbake" command.
Fetcher failure for URL: file://romulus.cfg
This is the config file required by the kernel. It's where you can put some additional kernel config parameters. For our purposes here, just modify romulus-prime to use the romulus.cfg file. We just need to add the -prime to the prepend path.
vi ./meta-ibm/meta-romulus-prime/recipes-kernel/linux/linux-aspeed_%.bbappend
FILESEXTRAPATHS_prepend_romulus-prime := "${THISDIR}/${PN}:"
SRC_URI += "file://romulus.cfg"
Re-run your "bitbake" command.
No rule to make target arch/arm/boot/dts/aspeed-bmc-opp-romulus-prime.dtb
The .dtb file is a device tree blob file. It is generated during the Linux kernel build based on its corresponding .dts file. When you introduce a new OpenBMC system, you need to send these kernel updates upstream. The linked email thread is an example of this process. Upstreaming to the kernel is a lesson in itself. For this lesson, we will simply use the Romulus kernel config files.
vi ./meta-ibm/meta-romulus-prime/conf/machine/romulus-prime.conf
# Replace the ${MACHINE} variable in the KERNEL_DEVICETREE
# Use romulus device tree
KERNEL_DEVICETREE = "${KMACHINE}-bmc-opp-romulus.dtb"
Re-run your "bitbake" command.
And you've finally built your new system's image! There are more customizations to be done but let's first verify what you have boots.
Your new image will be in the following location from where you ran your "bitbake" command:
./tmp/deploy/images/romulus-prime/obmc-phosphor-image-romulus-prime.static.mtd
Copy this image to where you've set up your QEMU session and re-run the command to start QEMU (qemu-system-arm command from dev-environment.md), giving your new file as input.
Once booted, you should see the following for the login:
romulus-prime login:
There you go! You've done the basics of creating, booting, and building a new system. This is by no means a complete system but you now have the base for the customizations you'll need to do for your new system.
There are a lot of other areas to customize when creating a new system. We'll dig into more detail with these (IPMI, HWMON, LED) in future development guides.
Although not in the same format as these guides, Porting_Guide provides a lot of very useful information as well on adding a new system.