If you compare the device tree as loaded by Linux, available in /sys/firmware/fdt, you will see that it differs from the one that you loaded in U-Boot. Taking the time to make the comparison is quite instructive.

Let’s do this on my Toradex Verdin iMX8M Mini SoM on the Dahlia carrier board.

Decompiling the DTB

It’s easy to decompile any Device Tree Binary (DTB) file using dtc, the Device Tree Compiler.

1. Copy /sys/firmware/fdt from your live Linux system to external storage (assuming your external storage is mounted on /mnt/usb)
   cp /sys/firmware/fdt /mnt/usb/linux.dtb

A variant of this article also exists as a conference presentation.

Do you already have a job in embedded Linux but wish to be given more challenging goals? Or are you in IT, already using Linux on your own laptop, and dreaming about landing an embedded Linux job, possibly starting as your own boss? Follow my advice in a patient and consistent way, and you will achieve your goals in less than 12 months.

Understanding Virtual Packages in Yocto Project / OpenEmbedded

If you are using Yocto, this post will help you learn about Virtual Packages: how they work, why they are useful, and how to create them step by step.

We assume you are already familiar with:

• Yocto Project setup

• Basic command of BitBake and recipe syntax

What is a Virtual Package?

Imagine you have multiple implementations of the same functionality (for example, different kernels such as a real-time kernel, a boot-time optimized kernel, and a kernel without loadable modules). Of course, your final image will include only one kernel, but you may want to keep several implementations in your project, so you can switch between them easily whenever you like.

Kernel Recipes conference in Paris
One of the best for Linux kernel topics 😉.
Recommended by Root Commit!

I discovered a intriguing phenomenon while preparing my How to test the latest mainline Linux kernel or bootloader presentation at OpenEmbedded Workshop 2025. It turned out there was something incomplete in my understanding of BitBake variable overrides.

Following discussions with a customer, and as a teaser for our Yocto Project and OpenEmbedded course, we are now offering a 1-day overview seminar on this topic.

The main goal is to give you a clear view of the Yocto Project and the value it can bring to your embedded Linux device projects. You will have a guided view of its main features and quick demos, all done in an engaging and interactive way.

Last week, I gave a “How to test a specific version of Linux on PC hardware” talk at the Alposs conference in Echirolles near Grenoble, France.

This was a very nice technical conference, with 330 participants (+110 compared to last year), organized in the city hall of Echirolles near Grenoble and by Belledonne Communications (the editors of Linphone) and OW2, an international association of Free Software professionals. Echirolles has a very dynamic orientation, deploying Free and Open Source Software in many of its services, thus improving the services offered to its citizens.

If you have other boards, read on, these instructions support multiple other Raspberry Pi boards.

Hardware

In this tutorial, we assume you have the Raspberry Pi Debug Probe to access the board’s serial port. You could use the GPIO UARTs too, but they are neither enabled by default at the bootloader level nor as a kernel console. Enabling them for serial console access would slightly complicate these instructions.

I’ve just produced a 4K video replay of my Devtool Hands-on Class at Yocto Project Summit 2024.12.

Here are the main reasons for shooting such a video:

• Compared to the official recording, this video is shorter without the pauses waiting for participants to complete their instructions.

• The video can be recorded at a better quality, both in terms of video and audio.

• The issues found during the presentation have been corrected.

• It’s possible to show presentation slides and command line terminals on the same screen.

The first sessions announced in 2024 are coming. We are opening in-person and online sessions open to individual registration, for our Embedded Linux and Yocto Project and OpenEmbedded training courses:

Yocto Project and OpenEmbedded
In-person – Feb. 25-28 2025, Avignon, France
Online – Mar 18-20, 25-27, 2025

Embedded Linux
Online, Apr. 14-17, 22-25, 2025
In-person, May 5-9, 2025, Avignon, France

Shared features

Both courses, online and in-person, share the same key features:

• 75% of active learning time through practical labs and activities. You won’t get more than 25% of the time going through theory.

Here are the slides of the “Building and Maintaining Binary Distributions with the Yocto Project” presentation I gave at the Embedded Linux Conference in Vienna.

The abstract I submitted is a good way to describe my presentation:

Imagine a world in which you can try the Yocto Project without even using it. This was possible in the past with the Ångström distribution, offering ready-made images which could be extended through binary package feeds. Though Ångström is long gone, the Yocto Project still has the ability to generate such images and package feeds. While system makers are still using this feature, the Yocto Project itself has never published such binaries.

The Yocto Project, thanks to funding from the Sovereign Tech Fund, has recently developed its abilities to support binary distributions, by creating tooling to verify the ability to upgrade the images built for its releases through package feeds, and to support managing a “local” distribution that can customize packages offered by an “upstream” distribution.

Since Yocto is about recipes, I will first present a cookbook for building your own images so that they can be updated through package feeds. I will then describe the recently developed features related to binary distributions and what possibilities they open for the Yocto Project and its users.