As described in previous articles (Introduction to PipeWire, Hands-on installation of PipeWire), the PipeWire daemon is responsible for running the graph execution. Nodes inside this graph can be implemented by any process that has access to the PipeWire socket that is used for IPC. PipeWire provides a shared object library that abstracts the communication with the main daemon and the communication with the modules that are required by the client.
In this blog post, our goal will be to implement an audio source node that plays audio coming from a file, in a loop. This will be an excuse to see a lot of code, showing what the library API looks like and how it should be used. To introduce some dynamism to a rather static setup, we’ll rely on an input from a Wii Nunchuck, connected using a custom Linux driver and relying on the input event userspace API.
Continue reading “A custom PipeWire node”
A few months ago, we started supporting SiFive in their effort to maintain and improve the Yocto support for their RISC-V processors and platforms. The Yocto support for SiFive platforms is divided into two layers:
These layers allow to build ready-to-use Yocto images for the Qemu RISC-V 64-bit emulation, the HiFive Unleashed and HiFive Unmatched development boards.
As part of our work on the Yocto support for SiFive platofrms, we have already published three new releases of these layers: 2022.06, 2022.08 and 2022.10. In this blog post, we review the main highlights of those releases.
Continue reading “Updated Yocto support for SiFive RISC-V platforms”
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.
In this blog post, we’ll discuss the phandle properties used in Device Tree. These properties are used to describe a relationship between components described in the Device Tree. Many blog posts describe this property from the Device Tree source point of view (you can for example have a look at https://elinux.org/Device_Tree_Mysteries#Phandle for details related to Device Tree source). In this blog post, we want to take a different approach, and discuss how to handle this type of property from the Linux kernel C code point of view.
Continue reading “Device Tree phandle: the C code point of view”
Capitole 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:
- being one of the gold sponsors of the event
- having a booth, through which attendees will be able to meet Bootlin engineers, discuss embedded Linux, projects, career and internship opportunities at Bootlin. Most of the Bootlin embedded Linux engineers based in Toulouse will be present at the event and the booth.
- giving 4 different talks (titles are in French, as talks are given in French):
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!
On recent GNU/Linux distributions such as Ubuntu 22.04 and 22.10, you may hit an issue creating a bootable FAT partition for embedded boards, at least with the TI AM335x processor, such as the 32 bit Beagle Bone boards.
Continue reading “Workaround for creating bootable FAT partition for Beagle Bone / AM335x on recent distros”
Bootlin is really happy to welcome another engineer in its team: Jérémie Dautheribes, who joined us on November 2, 2022.
Jérémie Dautheribes graduated in 2020 with a master degree in Ambiant, Mobile and Embedded Systems from the Toulouse University. After graduating, he worked at the french research institute INRIA on cache optimization for FreeRTOS multicore programs, and then in a company called EPSI where he was in charge of developing and maintaining Linux-based BSPs for i.MX6 and Tegra platforms, based on Yocto.
In addition, Jérémie has some experience in using the Rust programming language for low-level development, a skill that might prove to be useful for doing Linux kernel development in the future!
Jérémie is now joining our team located in Toulouse, France, where he will work at our office with Hervé Codina, Paul Kocialkowski, Köry Maincent, Thomas Perrot, Miquèl Raynal and Thomas Petazzoni.
For more details, see Jérémie’s page on Bootlin.com and his LinkedIn profile.
Since its inception, Bootlin has offered training courses on technical topics related to the use of Linux in embedded systems, with freely accessible training materials, and trainers with in-depth and real-life experience in their field. Based on these ideas, we have progressively extended our training portfolio over the years.
Today, we are extremely happy to announce a brand new course: Linux debugging, profiling, tracing and performance analysis. Many of our customers working on embedded Linux systems have expressed interest in diving into these complex topics, so we’ve created this course to:
- Give enough background information about how Linux works to be able to have a solid reasoning when investigating performance issues or simply bugs. Our course therefore details how user-space vs. kernel-space works, scheduling, and memory management, as a prerequisite to understanding better how Linux works.
- Give a strong introduction to the most important debugging, profiling and tracing tools in Linux, which are often not easy to get started with. We cover a very large spectrum of tools: strace, gdb, perf, ftrace, LTTng, kgdb, kmemleak, and many more. All these tools are illustrated through practical examples.
See the complete agenda for this course: debugging-online-agenda.pdf. The complete training materials will be freely available after the first session has been delivered, end of November 2022.
This course is currently being prepared by Bootlin engineer Clément Léger, who will also be teaching this course. Clément has a deep knowledge of how CPUs work and how Linux runs on a given CPU architecture, by having ported the Linux kernel to a brand new CPU architecture.
While the first session of this course will be delivered to a private customer, we have already scheduled a first public session which will take place on January 30, 31, Feb 1, 2, 2023, plus an extra session on Feb 3, 2023 if needed to cover all topics/questions. This session will take place each day from 14:00 to 18:00 UTC+1 (Paris time). Registration takes place directly online: the pricing is 569 EUR per seat at the discounted rate, or at 669 EUR per seat at the normal rate.
We can also organize a private session of this course for your team/company, either on-line or on-site: contact us to request a quote if you’re interested.
Linux 6.0 has been released two weeks ago, and Linux 6.1-rc1 is already out of the door, but we didn’t get the chance to look at the contributions made by Bootlin to the Linux 6.0 release. Before we do that, let’s provide our usual must-read articles on Linux 6.0: the Linux 6.0 merge window part 1 and Linux 6.0 merge window part 2 LWN.net articles and the KernelNewbies.org article.
On Bootlin side, our significant contributions to this release have been:
- Clément Léger contributed a new driver for the Ethernet switch found in the Renesas RZ/N1 processor, as well as a PCS driver for the MII converter of the same processor. Obviously, this came with the related Device Tree bindings and Device Tree changes, but also with a few small changes in the DSA subsystem.
- Hervé Codina enabled support for the PCIe controller found in the same Renesas RZ/N1 processor, which in fact does not allow to use PCIe devices, but USB devices: this PCIe controller is only used to connect to an internal USB controller in the chip, which therefore allows to use USB devices.
- Köry Maincent extended the existing mpc4922 DAC IIO driver to also support the mpc4921 variant, which has only one output channel instead of two.
- Luca Ceresoli contributed several improvements to the I2C subsystem documentation.
- Paul Kocialkowski contributed a new DRM driver for the logiCVC-ML display controller IP
- Paul Kocialkowski contributed two new V4L drivers for the MIPI CSI-2 camera interfaces available in the Allwinner A31 family of processors (sun6i) and the Allwinner A83T family of processors (sun8i).
Here is the full details of our contributions, commit by commit:
- Alexandre Belloni (2):
- Clément Léger (30):
- Herve Codina (6):
- Kory Maincent (2):
- Luca Ceresoli (11):
- Miquel Raynal (3):
- Paul Kocialkowski (7):
Here are the quickest instructions (I hope) for having the Yocto Project build an embedded Linux image for BeagleBone boards based on the TI AM335x CPU:
git clone -b kirkstone https://git.yoctoproject.org/git/poky
This gets you in a new
build directory. You can then generate your image:
MACHINE="beaglebone-yocto" bitbake core-image-minimal
Once the build is over, you can flash the image on a microSD card (assuming it’s mapped to
dd if=core-image-minimal-beaglebone-yocto.wic of=/dev/mmcblk0 bs=4M
More details for customizing images and supporting other boards in the Yocto Project manual.