Category: Conference

Feedback from ELCE 2023: selection of talks #4

As we reported in a previous blog post, almost the entire Bootlin engineering team was at the Embedded Linux Conference Europe in Prague in June. In order to share with our readers more about what happened at this conference, we have asked all engineers at Bootlin to select one talk they found interesting and useful and share a short summary of it. We will share this feedback in a series of blog posts: first post, second post, third post, this one being the fourth and final post of the series.

Do the Time Warp – the Rocky Horror PTP Show: Verification of Network Time Synchronization in the Real World

Talk by Johannes Zink, chosen by Bootlin engineer Köry Maincent

As we are currently dealing with PTP at Bootlin and facing several weird behaviors, this talk resonated well with our current state of mind. Currently, most of our clock usage uses NTP but some specific usage may need PTP to have high-precision clock synchronization between devices.

In this talk, Johannes first describes briefly the principles of PTP and its implementation in the Linux kernel, where the PTP is either managed by the MAC (often), the PHY or by software, and Userspace, with the description of the Linuxptp project. Then he goes straight to the issues he faced. For non-PTP users, it might be a bit harsh to follow the tests and oscilloscope measurements described by Johannes. He describes several possible issues and clock behaviors you can face, which might help a new PTP user to not spend too much time on debugging some tricky PTP behavior. Also one of the important things he notices is to “Always check your assumptions!”, which he wants to spread as a religious mantra. Using his common pitfalls and best practices may be a good thing when putting a hand in the PTP mechanism.

And don’t forget “Always check your assumptions!”!

Slides: PDF
Video: Youtube

Setting up Yocto Layers and Builds with Official Tools – 2023 Edition

Talk by Alexander Kanavin, chosen by Bootlin engineer Jérémie Dautheribes

As a Yocto user, you may have already wondered, ‘Why aren’t there official tools for creating and managing BitBake-based projects in a reproducible manner?’ Perhaps you have already used tools like repo, Git submodules, kas, or even created your own scripts.
In this talk, Alexander Kanavin – one of the major contributors to the Yocto project – introduces the tools currently under development within OE-core/poky to address this situation.

Slides: ODP
Video: Youtube

WirePlumber 0.5 Propelling PipeWire for the Embedded

Talk by Ashok Sidipotu, chosen by Bootlin engineer Alexandre Belloni

Ashok started to present a quick introduction to what Pipewire is. A nice block diagram explains what it looks like in action. Then the discussion switches to the session manager and why it is important.
WirePlumber is now the default session manager, replacing PipeWire media session. It manages the control path and dynamically creates PipeWire objects.
The main changes are:

  • config syntax is switching from Lua to SPA JSON, just like PipeWire. More info is available is this blog post
  • the event dispatcher has been created to handle PipeWire signals. This allows to prioritize signals and to avoid race conditions. This feature has a nice example and a fairly complete blog post

This talk is a nice overview of what is happening in the PipeWire ecosystem which is now quite mature. It is also great to see the improvements and that the embedded use case is not forgotten.

Slides: PDF
Video: Youtube

Feedback from ELCE 2023: selection of talks #3

As we reported in a previous blog post, almost the entire Bootlin engineering team was at the Embedded Linux Conference Europe in Prague in June. In order to share with our readers more about what happened at this conference, we have asked all engineers at Bootlin to select one talk they found interesting and useful and share a short summary of it. We will share this feedback in a series of blog post: first post, second post, this one being the third of the series.

rtla timerlat: Debugging Real-time Linux Scheduling Latency

Talk by Daniel Bristot de Oliveira, chosen by Bootlin engineer Maxime Chevallier.

Talks related to real-time linux debugging are pretty common at ELCE, I gave one myself in 2017 and I’ve been attending most of them since then. Besides a headache, what I could get from attending all these talks is that this topic is complex, time consuming, and that there’s a lot of different methodologies one can use to find the cause of these elusive problems.

Users who aren’t very familiar with the inner workings of the Linux Kernel can ask for help on mailing-lists, and the reply usually asks for a trace. This is where things get complicated, the Linux kernel tracer is very powerful, but can drown users in a flood of trace events from which it is difficult to extract the relevant data.

Hopefully, Daniel’s talk is going to make this kind of talk less common, as the tool he wrote and presented, rtla, makes it easy to gather important information about the cause of undesired latencies. By using cleverly placed trace-points, in-kernel testing tools (timerlat and osnoise) and an automated trace analyzer, rtla can not only detect latencies as cyclictest would, it can also give you what caused the latency. If it’s a blocking problem, rtla tells you which process is blocking your task. If it’s an interference, rtla will tell you which task or interrupt caused the latency, and can even detect if the hardware itself is the culprit.

For developers, this tool is also a perfect way to gather user feedback and bug reports that are small, precise and easily reproducible.

I therefore strongly recommend checking out Daniel’s talk and his dedicated blog article.

Slides: PDF
Video: Youtube

Zbus – the Lightweight and Flexible Zephyr Message Bus

Talk by Robrigo Peixoto, chosen by Bootlin engineer Thomas Perrot

Zbus is a new message bus for Zephyr allowing threads to communicate to many others, easily. This bus allows to implement several bus topologies:

    • one-to-one
    • one-to-many
    • Many-to-many

In addition, it can be used on very constrained systems.

In this talk, Rodrigo explained in detail how Zbus works, through a few examples. A thread can read or publish in bus channels, and when a message is published into a channel:

      • The Listener’s callbacks are executed
      • A notification is put to the subscriber’s queues
      • Then the subscriber will be executed by priority order

The bus is managed by a dispatcher, named Virtual Distributed Event Dispatcher (VDED) that is robust to priority inversion.

We found Zbus to be a very interesting feature because before there was no easy way to implement one-to-many and many-to-many topologies, but also one-to-one communications without having to manage the problems of inverting priorities and to use FIFO, LIFO, pipe, etc.

Slides: PDF
Video: Youtube

Linux Power ! (from the Perspective of a PMIC Vendor)

Talk by Matti Vaittinen, chosen by Bootlin engineer Kamel Bouhara.

PMICs (Power Management Integrated Circuit) are a key component of low power embedded systems as they often handle complexity in controlling various power voltages required by SoCs. In his talk Matti Vaittinen started by depicting the various devices that can be embedded in a PMIC (Power Management Integrated Circuit): watchdog, RTC, GPIOs are examples of such extra functionalities. He reminded us the reason why such devices are best fitted in the Linux MFD subsystem to take advantage of existing code. However the main subsystem used to implement support for a PMIC is the regulator subsystem and the talk gives us a good understanding of how it works, the concept of provider/consumer, how to register multiple regulators for a PMIC and how to handle specific events. A focus is made on error detection and how over current errors are reported over three categories:

      • PROTECTION : hardware level errors reported when protection limit is reached
      • ERROR: Unrecoverable errors that don’t directly involve hardware shutdown.
      • WARNING: System is still recoverable but requires specific action to be taken

Some PMICs also provide IRQs to notify errors or events and the kernel provides a helper function to handle such notifications and map them to specific actions depending on their severity.

Overall, we found this talk interesting to understand bettert the features provided by PMICs, and how these features are supported by Linux.

Slides: PDF
Video: Youtube

Bootlin at Embedded Recipes 2023: sponsor, talk and participant

Embedded Recipes 2023The Embedded Recipes conference was started a few years ago, modeled after the popular Kernel Recipes conference. Both events follow an unusual but very interesting format: a single-track conference, with a carefully chosen set of talks/speakers, and a limited number of attendees. These “design choices” give those events a different atmosphere than larger events, whether they are corporate-driven or community-driven.

This year, the Embedded Recipes conference will take place in Paris on September 28-29, with two full days of talks, but also opportunities to connect which are facilitated by the smaller audience and single-track nature of the event. The schedule is now online.

Bootlin has decided to support this year’s edition by being one of the Chef sponsors, contributing financially to the sustainability of this conference. In addition, Bootlin engineer Romain Gantois will give a lightning talk about Snagboot, our recently released open-source and HW agnostic tool to recover and reflash embedded platforms.

Finally, a number of Bootlin engineers will participate to Embedded Recipes: Michael Opdenacker, Paul Kocialkowski, Miquèl Raynal, Théo Lebrun, Romain Gantois and Thomas Petazzoni. Michael will also be present for Kernel Recipes at the beginning of the week.

If you’re interested in meeting with Bootlin folks, do not hesitate to reach out. Remember: we are still hiring, and looking for engineers with embedded Linux and/or Linux kernel experience to join our team. Meeting at this conference would be a great opportunity to start the conversation!

In the mean time, we can only recommend one thing: plan on attending the conference, and register now!

Feedback from ELCE 2023: selection of talks #2

As we reported in previous blog post, almost the entire Bootlin engineering team was at the Embedded Linux Conference Europe in Prague in June. In order to share with our readers more about what happened at this conference, we have asked all engineers at Bootlin to select one talk they found interesting and useful and share a short summary of it. We will share this feedback in a series of blog post: first post, this one being the second post.

Continue reading “Feedback from ELCE 2023: selection of talks #2”

Feedback from ELCE 2023: selection of talks #1

As we reported in previous blog post, almost the entire Bootlin engineering team was at the Embedded Linux Conference Europe in Prague in June. In order to share with our readers more about what happened at this conference, we have asked all engineers at Bootlin to select one talk they found interesting and useful and share a short summary of it. We will share this feedback in a series of blog post, this one being the first of this series.

Continue reading “Feedback from ELCE 2023: selection of talks #1”

Report from the Buildroot Developers Meeting at FOSDEM 2023

With the FOSDEM conference taking place on-site again after 2 years of virtual conference, this month of February also saw the return of the traditional Buildroot Developers Meeting from the Buildroot project.

This meeting is traditionnally held twice a year, around FOSDEM and around the Embedded Linux Conference Europe, and allows maintainers and contributors to the Buildroot project to gather for a few days and make progress on various tasks/topics.

This year, the post-FOSDEM Buildroot Developers Meeting took place on February 6, 7 and 8 in Brussels, and was hosted at the Smile offices, who kindly sponsored the location for the meeting.

Continue reading “Report from the Buildroot Developers Meeting at FOSDEM 2023”

Upcoming Yocto Project Summit 2022.11 – One talk from Bootlin

Headline of the Yocto Project Summit 2022.11.

As every six months for the last two years, a new virtual edition of the Yocto Project Summit is coming, and its schedule has been announced.

This summit will be over 3 days:

  • Tuesday, November 29
    Two tracks in parallel, a beginner track and a “hands-on” track for people already familiar with the concepts.
  • Wednesday, November 30
    Only one track, with intermediate level talks on all kinds of topics.
  • Thursday, December 1
    Only one track, starting with “product showcase” talks and going on with intermediate level talks on various topics too.

Last but not least, at the end of each day, you will get a chance to hangout with other contributors and users, and ask all the questions that you may have.

Bootlin is proud to contribute one talk to this summit: Bitbaking SPDX SBoM which we will prepare and present. This talk will cover one of the topics we explored to document features of the Yocto Project which had no documentation yet. SPDX and SBoM are related to software supply chain security, vulnerability management and license compliance. These are hot topics these days, and there will be another presentation about SBoMs (SBoMs and Supply Chain with the Yocto Project by Joshua Watt), and two about security (Detecting and fixing CVE security issues in yocto based embedded Linux distribution by Mikko Rapeli, and Maintenance and Security of a Yocto Project-based Distribution: A Year of Experiences by Marta Rybczynska).

Bootlin is indeed involved in the Yocto Project by maintaining its documentation (see the active contributors through the git repository), and also a participant to the Yocto SWAT team, keeping track of all the issues encountered by the autobuilder machines and runs.

Though the Yocto Project and OpenEmbedded are Open Source projects, registration for this conference is not free but just costs 40 USD, to cover infrastructure and staffing costs, the event being hosted by the Linux Foundation.

Bootlin at Capitole du Libre 2022: sponsor, booth and talks

Capitole du Libre 2022Capitole du Libre is a free-software/open-source conference with a local/regional scope organized in Toulouse, France, since ~2012. As one of the Bootlin offices is also located in Toulouse, Bootlin has often participated to this event by giving talks or simply by attending.

The 2022 edition, the first after 2 years of interruption due to the COVID19 crisis, will take place on November 19 and November 20. Bootlin will participate by:

If you’re in the Toulouse area and a free-software/open-source enthusiast, we strongly recommend you to attend Capitole du Libre. The event is free, no registration is required, and there’s a very nice line-up of talks and workshops!

Bootlin at Linux Plumbers conference 2022

Next week, almost the entire Bootlin team will be at the Embedded Linux Conference Europe in Dublin, see our previous blog post on this topic. We will give four talks at this event, on a variety of Linux kernel and embedded Linux topics.

During the same week, also in Dublin albeit in a different location, will take place the Linux Plumbers conference. Bootlin engineer Miquèl Raynal will give a talk at Linux Plumbers, as part of the IoTs a 4-Letter Word micro-conference. Miquèl’s talk will discuss Linux IEEE 802.15.4 MLME improvements, as Miquèl has been working for several months on bringing improvements to the 802.15.4 stack in the Linux kernel.

Embedded Linux Conference Europe 2022: four talks from Bootlin

The schedule for the upcoming Embedded Linux Conference Europe 2022 has been published recently.

Bootlin CEO Thomas Petazzoni is again a member of the program committee for this edition of ELCE, and has helped with other members of this committee in reviewing and selecting the numerous talk submissions that have been received.

Bootlin will obviously be present at this conference. With 13 engineers from Bootlin participating, almost the entire company will be in Dublin for this major event of the embedded Linux community. Also, 4 of the talks that we had submitted have been accepted:

  • Luca Ceresoli on Basics of I2C on Linux
    This talk is an introduction to using I²C on embedded Linux devices. I²C (or I2C) is a simple but flexible electronic bus to allow low-speed communication between the CPU and all sorts of chips: PMICs, ADC/DACs, GPIO expanders, video sensors, audio codecs, EEPROMS, RTCs and many more. It is so popular that knowing it is a must for any embedded system engineer. Luca will first give an introduction to what I2C is at the electrical level. He will then describe how I2C is implemented in the Linux kernel driver model and how that appears in sysfs, how to describe I2C devices using device tree and how to write a driver for an I2C device. Finally he will present the tools to communicate with the chips from userspace and share some debugging techniques, including inspection of the physical bus and software-level debugging.
  • Miquèl Raynal on Improving Wireless PAN Support
    Anybody eager to learn about IoT devices has at least once tried to play with Zigbee or 6lowpan sensors. These two protocols are built on top of a well common MAC/PHY specification: IEEE 802.15.4, also known as Wireless Personal Area Networks: WPAN, designed to be low-rate/low-range wireless networks. There is already substantial support for this protocol in the Linux kernel but when my journey started, several of the MAC-related operations well described in the specification were not implemented, making the subsystem mainly useful for very simple use cases: peer-to-peer transmissions. This is unfortunate as a significant part of the idea behind WPAN is to make these networks quite adaptive and resilient, which requires a minimal subset of the peer management procedure to be supported. Besides a number of preparation changes, the main idea behind the continuous flow of patches was to bring support for the scanning procedure which allows a PAN controller to detect all the compatible devices around it in different ways. Discovering these devices is the first step in order to associate them together and build up starred networks. This talk will be an opportunity to explain the new APIs allowing such discoveries and provide a state of the art of the support in the mainline kernel.
  • Michael Opdenacker on Implementing A/B System Updates with U-Boot
    A popular way to implement system updates is through the A/B scheme, in which you have two copies of the root filesystem, one which is active, and one that is meant to contain the next update. When a new update is successfully applied, you need to make the corresponding partition become the new active one. That’s when a number of practical questions arise, such as how to identify the active partition, how to detect when the new system fails to boot properly, and how to fall back to the previous version? It was hard to find documentation about how U-Boot could address such needs to implement a functional and failsafe A/B system update mechanism. This presentation proposes to address this need by sharing the practical solutions we found, using lesser known commands and capabilities in U-Boot. We will also explain how the Linux side can cooperate with the U-Boot side. Fortunately, you won’t need to erase half of your brain to get updated on this topic.
  • Paul Kocialkowski on Walking Through the Linux-Based Graphics Stack
    The graphics stack used with the Linux kernel is a notoriously complex beast. From userspace down to the kernel level, a number of components are involved and interact with eachother. It is also an area that is constantly evolving to meet new use cases, refresh legacy implementations and achieve better performance. This makes it difficult to have a clear idea of the big picture and what is actually happening when using graphics-related components. This presentation will detail a walk through the graphics stack, with actual examples of displaying a buffer and rendering using the GPU. Going from the application level through the system libraries, down to the kernel and ending with actual hardware configuration. State-of-the-art technologies such as Wayland and DRM will be highlighted with relevant excerpts from the source code of related free software projects that are widely used today.

We look forward to meeting again the embedded Linux community, its developers, users and maintainers, at Dublin during this conference!