During a 3-day week-end, between March 31 and April 2, the Buildroot project organized a hackathon in Paris with six core/active developers of the project. The goal of this meeting was to make progress on outstanding patch series and reduce the backlog of contributions waiting in the project patchwork. Thomas Petazzoni, CTO and embedded Linux engineer at Bootlin participated to the event, joining Arnout Vandecappelle, Peter Korsgaard, Yann E. Morin, Romain Naour and Maxime Hadjinlian in the fantastic location provided by Scaleway.
Thomas summarized the progress day by day in three separate e-mails sent on the mailing list:
Merge of a patch series from Yann E. Morin that reworks how filesystem images are generated, to make this process compatible with top-level parallel build.
Merge of a patch series from Maxime Hadjinlian (with significant contributions from Yann E. Morin) that implements caching of Git downloads, significantly reducing the time needed to clone different versions of the same project through Git, especially big projects like the Linux kernel. An extensive summary of the changes was posted by Thomas on the mailing list.
Merge of a golang-package infrastructure, contributed by Angelo Compagnucci, to help building packages written in Go, and using the standardized Go build system.
The check-package tool was extended to validate the coding style of files outside the package/ folder, thanks to a contribution from Ricardo Martincoski.
Arnout worked on a significant number of pending Qt5 patches, and specifically merged the bump to Qt 5.10.
The LLVM patch series from Valentin Korenblit was reviewed, and thanks to this work, the initial LLVM package was merged a few days after the hackathon.
Last but not least, a large number of patches sitting in patchwork have been discussed, and either applied (after some rework) or reviewed (with comments made on the mailing list).
In total, 222 commits have been pushed to the master branch during this meeting, and the backlog of patches has reduced from ~350 patches to ~175 patches.
Once again, the Buildroot community would like to thank Scaleway for hosting this event! The next Buildroot meeting will most likely take place right before the Embedded Linux Conference in Edinburgh, on October 20-21.
Early February, we announced the launch of our first Kickstarter campaign, whose goal was to add support for the video decoding unit found in most Allwinner processors to the official Linux kernel.
We were very pleased to see that in just one day, enough companies and individuals participated to fund the main goal of the campaign, collecting more than 17,600 EUR. And now that the campaign is over since March 18, we are even more pleased, as we have reached a funding level sufficient to cover not only our main goal, but also our two first stretch goals.
Thanks to the participation of all those companies and individuals, we will be able to:
Deliver our main goal, which we expect to deliver by the end of June 2018, which includes:
Making sure that the codec works on the older Allwinner SoCs that are still widely used: A10 (Cubieboard), A13 (A13-Olinuxino), A20 (Cubieboard 2, A20-Olinuxino), A33 (A33-Olinuxino, BananaPi M2-Magic), R8 (CHIP) and R16 (NES and Super NES classic). Support for the newer SoCs (H3, H5 and A64) requires more work, and is part of our first stretch goal below.
Polishing the existing MPEG2 decoding support to make it fully production ready.
Implementing H264 video decoding, since H264 is by far one of the most popular video codec.
Modifying the Allwinner display driver in order to be able to directly display the decoded frames instead of converting and copying those frames, which is very inefficient from a CPU consumption point of view
Providing a user-space library easy to integrate in the popular open-source video players
Upstreaming those changes to the official Linux kernel
Deliver our two first stretch goals, which we expect to deliver by the end of 2018, which includes:
Supporting the newer Allwinner SoCs, such as the H3 (Most of the Orange Pis, Nano Pi M1, ..), H5 (Orange Pi PC2, NanoPi NEO2, …) and A64 (Pine64, BananaPi M64, …).
H265 video decoding support
Unfortunately, our third stretch goal, which consisted in adding support for H264 encoding was not reached, so we don’t know yet if we will have enough time to look into this topic.
However, the work on the other topics has already started, with our intern Paul Kocialkowski has started to work since March 1st on this Allwinner VPU effort, and Maxime Ripard has started this week. We have already published, will continue to publish a report every week: week 10, week 11 and week 12. You can follow the progress of this project by reading our blog, our Twitter feed or the Kickstarter updates. You can also read the Sunxi-cedrus Wiki page to get all the details about this project and its progress.
Beyond the specific topic of the Allwinner VPU support, we are very happy to see that the model of funding upstream Linux kernel work through crowd-funding has worked. Most Kickstarter projects, in exchange for the participants contribution, provide to the participant a specific product (a book, a device) that only benefits to the contributor. Here, the result of this campaign will be shared freely with everybody, both Kickstarter contributors and non-contributors, and we’re proud to see that our experience has convinced numerous companies and individuals to support our project. Of course, we will be organizing in the near future the shipment of the t-shirts as well as the beer drinking sessions with Bootlin engineer Maxime Ripard.
To conclude, we would like to thank all our participants (we’re naming only the ones who baked at a level above 16 EUR, as above this level contributors are going to be mentioned in the CREDITS file, which clarifies their intent to be publicly named). First a number of companies supported our work: OrangePi, Libre Computer, neutis.io, FriendlyArm, Pine64, Olimex and of course a huge number of individuals: Abe Lacker, Adam Morris, Adam Oberbeck, Alerino Reis, Alex, Alexander A. Istomin, Alexander Kamm, Alexandru Nedel, Alex Kaplan, Amarpreet Minhas, André, Andreas, Andreas Färber, Andreas Rozek, Andre Przywara, Andrew Langley, Angel Rua Amo, Anssi Kolehmainen, Antony, Appreciation of Efforts, Aron Somodi, Artur Huhtaniemi, Atsushi Sasaki, Bastien Nocera, Bavay, Benjamin Glass, Benjamin Larsson, Ben Young, Bernard D’Havé, Bert Lindner, Bert Vermeulen, BESSIERES MARC, Biji-san, Bob Black, brot, Bruce Shipman, Butterkeks, Carla Sella, Carl Wall, Carsten Tolkmit, cbrocas, chae, Charlie Bruce, Christian Gnägi, Christian Pellegrin, Christian Stalp, Christophe Vaillot, Christoph Kröppl, Conan Kudo (ニール・ゴンパ), D1don, Dale Cousins, Daniel, Daniel Hrynczenko, Daniel Kulesz, Daniel Mühlbachler, David Pottage, David Willmore, defsy, Denis Bodor, DESSARD Guy, Dimitrios Bogiatzoules, Dominique Dumont, Doyle Young, Dubouil, Eelco Wesemann, eineki, Emil Karlson, Emmanuel Fusté, Erdem MEYDANLI, Eric des Courtis, Eric Jensen, Eric Koorn, Éric Périé, Erik, erikf, Evaryont, Fabian Korak, Felix Eickeler, Flo, Florian Beier, Florian Kempf, Frank, Frank van Kesteren, Frederir, G40, Gabor, Gabriel Ortiz, Garrett Gee, Georg Ottinger, Gerald Hochegger, Geralt, ghostpatch, Gianpaolo Macario, Giulio Benetti, Guenther Gassner, Guilhem, Guilhem Saurel, hackman, Hamish, Hanno Helge, Hans-Frieder Vogt, Heinz Thölecke, Henrik Kuhn, hook, Hugh Reynolds, Ian Daniher, iav, Inapplicable, Ingo Strauch, Ioan Rogers, Irvel Nduva, James, James Cloos, James Valleroy, jan koopmanschap, Jared Smith, Jari-Matti, Jarkko Pöyry, Jasper Horn, jean, Jean-Pierre Rivière, Jeffrey Sites, Jernej, Jerome Hanoteau, JK, John Kelley, Johnny Sorocil, Juanjo Marin, Jussi Pakkanen, Justin Ross, Karl Palsson, Kazım Rıfat Özyılmaz, Kean, Kevin Fowlks, Kevin Read, kicklix, Kiesel, Koen Kooi, Korbinian Probst, kratz00, Laurent GUERBY, Lee Donaghy, liushuyu, Logicite, luigi, Lukas Schauer, lzrmzz, Maksims Matjakubovs, Manuel, Marcel Sarge, Marcus Cooper, Mario Villarreal, Mark Dietzer, Markus Härer, Martijn Bosgraaf, mateuszkj, Mathias Brossard, mathieu, Matsumoto Kenichi, Matthew Zhang, Matthias, Matthias Lamm, Matt Mets, Maxime Brousse, Me, MESNIL Mikaël, Michael Gregorowicz, Michael Thalmeier, Michal Zatloukal, Mirko Vogt, mouren, N/A, naguirre, Neil Davenport, Nick Crasci, Nick Richards, Oleksij Rempel, oliver, Oliver Heyme, OSAKANA TARO, othiman, ozcoder, Pablo, Patrick, Paul Philippov, Paul Sykes, Per Larsson, Peter Gnodde, Peter Robinson, Philip-Dylan Gleonec, Phipli, Phoenix Chen, Pierce Lopez, Priit Laes, Prisma, Rainer Stober, Reignier, René Kliment, Reto Haeberli, Ricardo Salveti de Araujo, Richard Cote, Richard Ferlazzo, Riku Voipio, Robert Lukierski, Robert McQueen, roens, Rui Gu, Ryan Casey, Salvatore Bognanni, Samuel Frederick, Scott Devaney, Sebastian Krzyszkowiak, Sébastien DA ROCHA, Sergey Kopalkin, Sertac Tulluk, Shelby Cruver, Shervin Emami, SIMANCAS, Simon Josefsson, Spas Kyuchukov, ssam, Stan, Stanislav Bogatyrev, Stas, Stefan Bethke, Stefan Monnier, Steffen Elste, Stephan, Stephan Bärwolf, Stephen Kelly, Steven Seifried, Stokes Gresh, Sven Kasemann, SvOlli, Tarjei Solvang Tjønn, Tetsuyuki Kobayashi, Texier Pierre-jean, Thomas Monjalon, Thomas Samson, Tim Symossek, Todd Zebert, Tomas Virgl, tpc010, Tyler Style, Valentin Hăloiu, valhalla, Vasily Evseenko, Vitaly Shukela, Xavier Duret, Yannick Allard, Yves Serrano, Zoltan Herpai, ZotoPatate, zym060050.
Back in June last year, we launched a new service that provides pre-compiled and ready-to-use cross compilation toolchains for a large number of CPU architectures and C library configurations. They are available from toolchains.bootlin.com.
We have recently updated those toolchains, with the following improvements:
Our stable family of toolchains has been updated in terms of components versions: we’re using gcc 6.3.0, binutils 2.29.1, gdb 7.11.1, kernel headers 4.1, glibc 2.26, musl 1.1.18 and uClibc 1.0.28
Our bleeding-edge family of toolchains has also been updated in terms of components versions: we’re using gcc 7.3.0, binutils 2.30, gdb 8.0.1, kernel headers 4.9.80, glibc 2.27, musl 1.1.8 and uClibc 1.0.28
The tarballs now have a more nice-looking version number, and the version number is also included in the directory after extracting the tarball
Qemu testing of the PowerPC64 little-endian configuration was added
Mid-March of this year, 8 engineers from Bootlin attended the Embedded Linux Conference North-America in Portland, Oregon. We had a strong presence at this conference with 5 talks, one BoF and two E-ALE tutorial sessions.
In this first blog post about ELC 2018, we want to share the slides and videos of the talks we gave during the conference.
Buildroot: What’s new? – Thomas Petazzoni
Buildroot is a popular and easy to use embedded Linux build system. Within minutes, it is capable of generating lightweight and customized Linux systems, including the cross-compilation toolchain, kernel and bootloader images, as well as a wide variety of userspace libraries and programs.
After a short introduction about Buildroot, this talk will go through the numerous new features and improvements that have appeared in the last few years, and show how they can be useful for developers, users and contributors.
This talk is an updated version of the one given at ELCE 2017.
NAND flash chips are almost everywhere, sometimes hidden in eMMCs, sometimes they are just parallel NAND chips under the orders of your favorite NAND controller. Each NAND vendor follows its own rules. Each SoC vendor creates his preferred abstraction for interacting with these chips.
Handling all of that requires some abstraction, and that is currently being enhanced in Linux! A new interface, called exec_op is showing up. It has been designed to match the most diverse situations. It should ease the support of advanced controllers as well as the implementation of vendor-specific NAND flash features.
This talk will start with some basics about NAND memories, especially their weaknesses and how we get rid of them. It will also show how the interaction between NAND chips and controllers has been standardized over the years and how it is planned to drive NAND controllers within Linux.
Secure Boot from A to Z – Quentin Schulz & Mylène Josserand
Based on our complementary experience on building a secure system on an i.MX6 custom board, we’ll present how to build a complete chain-of-trust for a platform.
This talk will introduce each and every link of the chain-of-trust from the boot ROM to filesystem, as well as the bootloader and kernel with real life examples.
We’ll go through everything needed from the signing of binaries (U-Boot and kernel) to the secured automation of kernel booting within the bootloader, the use of dm-verity and switchroot for securing the filesystem, and more.
I + I2C = I3C: What’s in this Additional ‘I’? – Boris Brezillon
The MIPI Alliance recently released version 1 of the I3C (pronounce ‘eye-three-see’) bus specification, which is supposed to be an improvement over the long-standing I2C and SPI protocols. Compared to I2C/SPI, I3C provides a higher data rate, lower power consumption and additional features such as dynamic address assignment, host join, in-band interrupts. For the last year or so, Free Electrons has been working with Cadence Design Systems on supporting this new kind of bus in Linux.
With this talk we would like to introduce this new bus and the concepts it brings to the table. We will also detail how we plan to expose the new features exposed by the I3C protocol in Linux and go through future possible improvements of the I3C framework that has already been submitted for review on the Linux kernel mailing list.
Introduction to Linux Kernel Driver Programming: i2c drivers – Michael Opdenacker
For people new to Linux kernel driver programming, writing a driver for an I2C device is a relatively easy way to start. This presentation will start by explaining the Device Model, the mechanism that the Linux kernel offers to bind drivers to devices. Even though the way to detect or describe devices can depend on the bus or CPU architecture, the infrastructure binding devices with drivers is universal and therefore applies to all types of device drivers in the Linux kernel. You will see how the driver uses one of the frameworks offered by the Linux kernel to expose device data to user space in a generic way. Once again, this type of mechanism is used everywhere in the Linux kernel.
Michael presented this topic as part of the E-ALE track, we’ll update this blog article once the recording is available to embed the video.
This “Birds of a Feather” session will start by a quick update on available resources, patches and recent work to reduce the size of user-space and of the Linux kernel (in particular the efforts from Nicolas Pitre).
An ARM based system running the mainline kernel with about 3 MB of RAM will also be demonstrated.
If you are interested in the size topic, please join this BoF and share your experience, the resources you have found and your ideas for further size reduction techniques! This BoF will build upon the one run at the latest Embedded Linux Conference in Europe.
We’ll update this blog article once the recording is available to embed the video.
Getting Started with Buildroot – Thomas Petazzoni
Need to create simple and optimized Linux systems for your embedded devices? Tired of complicated tools? You should try Buildroot!
In this tutorial, we will first introduce Buildroot, a popular embedded Linux build system, that allows you to build your own cross-compilation toolchain, Linux kernel and bootloader images, as well as root filesystem with your selection of user-space libraries and applications, all from an easy-to-use “menuconfig” interface.
Thomas presented this topic as part of the E-ALE track, we’ll update this blog article once the recording is available to embed the video.
Ethernet Switch Support in the Linux Kernel – Alexandre Belloni
Hardware Ethernet switches are appearing on more SoC families and can take care of many network functionalities like VLAN tagging, IGMP snooping, link aggregation,… Linux is able to offload network processing to those switches using the switchdev and the DSA APIs.
This talk will introduce the Ethernet switches and their typical features, the Linux switchdev and DSA APIs and their differences. It will also give an overview of sample implementations and how to use the features from userspace.
Like every year for more than 10 years, Bootlin engineers will participate to the next Embedded Linux Conference, which takes place in Portland on March 12-14. Of course, it will be our first ELC with our new company name! In total, eight engineers from Bootlin will participate to the event. Maxime Chevallier, who joined Bootlin last Monday, will be attending the conference, his first one with a Bootlin hat (but Maxime has already been a speaker at the last Embedded Linux Conference Europe).
We will also be giving a number of talks, tutorials or moderating Bird of a Feather sessions:
Miquèl Raynal will give a talk titled Drive your NAND with Linux, sharing his experience rewriting the NAND controller driver for Marvell platforms, significantly improving the NAND core subsystem along the way, making it more flexible to support advanced NAND controllers.
We’re really happy to again meet the embedded Linux open-source community at this event! It is worth mentioning that following this event, Bootlin CTO Thomas Petazzoni will be in the Silicon Valley on March 15-16, available for business meetings: do not hesitate to contact us if you’re interested.
Back in 2012, Bootlin (formerly Free Electrons) engineer Maxime Ripard pioneered the support for Allwinner processors in the official Linux kernel. Today, thanks to the contributions of numerous developers around the world and our involvement, there is very good support for a large number of Allwinner processors in the Linux kernel, to the point where actual Allwinner-based products are shipping with the mainline kernel.
Despite this major effort, there is one area that has remained unsupported in the mainline kernel: the video decoding and encoding engine, which allows to accelerate in hardware the decoding and encoding of popular codecs such as MPEG2, MPEG4 or H264. Last summer, we successfully implemented a prototype, supporting MPEG2 decoding and partially MPEG4 decoding.
Today, we are launching a crowdfunding campaign to fund the remainder of the development: finishing MPEG4 decoding support, implementing H264 decoding, optimizing the rendering of video frames in cooperation with the display driver, and upstreaming the driver. We also have additional goals of supporting H265, encoding support, and additional Allwinner SoCs.
In the vendor-provided kernel, this video decoding/encoding unit is supported by a kernel driver that uses a non-standard user-space API, in conjunction with a binary-only userspace blob. Fortunately, a number of people have done an enormous reverse engineering effort, which we have leveraged for our existing prototype, and which we intend to use to continue the development of this upstream driver. Both Maxime Ripard and our intern Paul Kocialkowski will be working on this crowdfunded project.
This is our first crowdfunding campaign to fund upstream Linux kernel development, and we are interested in seeing how much interest there is in such a financing model. Help us making this a success by spreading the word!
Beyond participating to the event, Maxime and Thomas also presented briefly on two topics:
Maxime Ripard brought up the topic of handling foreign DT bindings (see slides). Currently, the Device Tree bindings documentation is stored in the Linux kernel source tree, in Documentation/devicetree/bindings/. However, in theory, bindings are not operating-system specific, and indeed the same bindings are used in other projects: U-Boot, Barebox, FreeBSD, Zephyr, and probably more. Maxime raised the question of what these projects should do when they create new bindings or extend existing ones? Should they contribute a patch to Linux? Should we have a separate repository for DT bindings? A bit of discussion followed, but without getting to a real conclusion.
Thomas Petazzoni presented on the topic of avoiding duplication in Device Tree representations (see slides). Recent Marvell Armada processors have a hardware layout where a block containing multiple IPs is duplicated several times in the SoC. In the currently available Armada 8040 there are two copies of the CP110 hardware block, and the Linux kernel carries a separate description for each. While very similar, those descriptions have subtle differences that make it non-trivial to de-duplicate. However, future SoCs will not have just 2 copies of the same hardware block, 4 copies or potentially more. In such a situation, duplicating the Device Tree description is no longer reasonable. Thomas presented a solution based on the C pre-processor, and commented on other options, such as a script to generate DTs, or improvements in the DT compiler itself. A discussion around those options followed, and while tooling improvements were considered as being the long-term solution, in the short term the solution based on the C pre-processor was acceptable upstream.
For Free Electrons, participating to such events is very important, as it allows to expose to kernel developers the issue we are facing in some of our projects, and to get direct feedback from the developers on how to move forward on those topics. We definitely intend to continue participating in similar events in the future, for topics of interest to Free Electrons.
Back in August 2017, Free Electrons contributed to the Linux kernel a patch series adding support for the new MIPI I3C bus, a bus that aims at replacing busses like I2C and SPI, by offering better performance, lower power consumption, and new features like discovery, in-band interrupts and hot join.
At the time of our submission, the I3C specification was closed, but a few days ago, the MIPI Alliance announced that the I3C specification was now publicly available. This is of course very good news as it will allow a much easier and wider adoption of I3C, and it was a somewhat unexpected move since the MIPI Alliance had traditionally kept its specifications only for its members. Hopefully the I3C experience will encourage the MIPI Alliance to follow the same direction for existing or future protocols.
With this announcement from the MIPI Alliance, it was time for us to submit an updated version of our I3C support for the Linux kernel, which Free Electrons engineer Boris Brezillon did on Thursday: [PATCH v2 0/7] Add the I3C subsystem. Compared to the previous version submitted in August, this new version has interesting improvements:
A generic infrastructure to support IBIs (in-band interrupts) was added
Helpers to support hot-join were added to the core I3C subsystem
The Cadence I3C controller driver was improved to support IBIs and hot-join
And of course, many of the comments received on the first iteration have been addressed
With the specification now public, we hope to receive useful comments and feedback from the Linux kernel community to improve, and hopefully in the near future, merge the support for the MIPI I3C bus.
Earlier this month, Free Electrons engineer Alexandre Belloni posted a patch series (in its second version) adding initial support for Microsemi Ocelot SoCs, the VSC7513 and VSC7514. These SoCs are used for switches, so the biggest part of the chip is a switch fabric, built around a MIPS core and a few basic peripherals. While Free Electrons generally works on ARM platforms and has contributed support for numerous ARM processors in the Linux kernel, for this project we are contributing the support for a MIPS processor.
Alexandre’s initial patch series contains the basic support for the SoC:
All in all, this patch series only adds support to boot the platform up to a shell, with interrupts, pin-muxing, GPIOs and UARTs enabled. Additional features will be contributed later, especially support for the switch fabric in the form of a switchdev driver.
We are happy to be working on Microsemi platforms, and to bring the support for yet another hardware platform to the official Linux kernel.
During the closing session of this conference, Free Electrons CEO Michael Opdenacker has received from the hands of Tim Bird, on behalf of the ELCE committee, an award for its continuous participation to the Embedded Linux Conference Europe. Indeed, Michael has participated to all 11 editions of ELCE, with no interruption. He has been very active in promoting the event, especially through the video recording effort that Free Electrons did in the early years of the conference, as well as through the numerous talks given by Free Electrons.
Free Electrons is proud to see its continuous commitment to knowledge sharing and community participation be recognized by this award!