This week, Paul worked on preparing a new version of the patch series introducing support for the Sunxi-Cedrus VPU kernel driver, based upon the latest version of the Request API as submitted for review by Hans Verkuil on Monday. In order to make it easier to test the kernel driver, a standalone tool was written to decode a single frame (that was dumped beforehand). Support for displaying the decoded frame directly into a DRM plane was also added later this week, providing direct visual feedback. Finally, significant work was put into our libVA backend, that saw a significant rewrite of the memory-management logic related to video buffers.
We plan to prepare and release this new standalone tool as well as the libVA improvements when the kernel driver patch series is ready for submission, sometime next week. Specific instructions to get this up and running will also be made available on the Sunxi-Cedrus page of the linux-sunxi wiki, for one of the supported platforms. So far, we have tested the series on A33 and A20, but it is very likely that A10 and A13 will work just as well.
On his side, Maxime continued his effort on the H264 decoding. He first looked at the Chrome OS kernel and userspace code to drive the Rockchip SoCs VPU. This code is of interest because it’s basically the only stack so far that is functional, used and based on the Request API since Google is especially involved in the development of that API. He then went on with mapping the request API controls for H264 to the code for H264 decoding in the libvdpau-sunxi code that already provides an implementation for the Allwinner VPU. He then started to write some kernel code to add support for the kernel part of the API.
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.
This week has seen progress on the GStreamer front: the segmentation fault that was a blocker when interfacing our libva backend with gstreamer-vaapi was investigated and understood. An associated bug was reported to the GNOME bug tracker, with all the gory details attached. Since the issue was in fact due to the assembly routine imported from libvdpau-sunxi smashing the malloc heap metadata, the bug report was closed. Using valgrind proved very useful for diagnosing the issue. Since we are not going to keep using the software-based untiling method through this assembly code, no time was spent on investigating and fixing the issue there.
The integration of changes in GStreamer for our case is also moving forward, with the submission of newer iterations of the related patches when requested. There are still issues left to fix with GStreamer, although things are looking better and better. Plenty of small bugs and mistakes have been identified and resolved in both our kernel driver and VAAPI backend in the process.
A new version of the request API has also been submitted for review and comments by Hans Verkuil. We have started rebasing our VPU driver on top of this new version and hope to send out this new version sometime next week.
We also started to look into H264, mostly by setting up a good test scenario for H264 (using the libvdpau-sunxi and an Allwinner kernel), making sure that it can actually decode H264 videos (which it does), and building similar setup with the mainline kernel and our libva implementation.
Stay tuned for more development updates related to Allwinner VPU support in mainline Linux!
According to LWN statistics, Bootlin stands at the 13th place in the company ranking in terms of number of lines changed and we even have one of our engineers, Miquèl Raynal, appearing in the top 20 contributors with regards to number of lines changed thanks to his complete rework of the Marvell NAND controller driver and his addition of the exec_op() API to the NAND framework.
The main highlights of our contributions are:
For Marvell platforms,
Antoine Ténart improved the inside-secure crypto accelerator driver to support the EIP97 variant of the hardware block, which is used on the Marvell Armada 3700. This driver was already supporting the EIP197 variant, used on Marvell Armada 7K/8K. This new EIP97 support allows to enable the use of the crypto accelerator on the popular EspressoBin platform, a $49 board based on the Marvell Armada 3700,
Antoine Ténart also contributed a number of fixes to the inside-secure crypto accelerator driver,
Antoine Ténart also contributed a few fixes to the mvpp2 network driver, used for the Ethernet controller on the Marvell Armada 7K/8K.
Both Boris Brezillon and Miquèl Raynal contributed numerous fixes,
Miquèl Raynal contributed the exec_op API to simplify how NAND controllers interact with the core with regards to sending NAND operations. For more details about Miquèl’s work, see the video and slides of his talk at the latest ELC,
For Microsemi Ocelot platforms:
Alexandre Belloni added support for Microsemi Ocelot SoC’s pinctrl. This is the very first piece of the support for the Microsemi VSC7513/7514 MIPS processors, with the rest of the basic platform support expected to appear in 4.17,
Maxime Ripard added support for LVDS for the A83T in the DRM subsystem and contributed a few fixes along the way,
Mylène Josserand added ADC support for the audio codec present on the sun8i family,
Alexandre Belloni fixed a few race conditions in the AC100 RTC driver,
Maxime Ripard also contributed a fix for gpiolib failing to defer its probing until a GPIO controller is registered,
Bootlin engineers are not only contributors, but also maintainers of various subsystems in the Linux kernel, which means they are involved in the process of reviewing, discussing and merging patches contributed to those subsystems:
Maxime Ripard, as the Allwinner platform co-maintainer, merged 66 patches from other contributors
Boris Brezillon, as the MTD/NAND maintainer, merged 73 patches from other contributors
Alexandre Belloni, as the RTC maintainer and Atmel platform co-maintainer, merged 23 patches from other contributors
Grégory Clement, as the Marvell EBU co-maintainer, merged 16 patches from other contributors
Here is the commit by commit detail of our contributons to 4.16:
As discussed in our previous blog post, Bootlin had again a strong presence at the Embedded Linux Conference North-America, with 8 attendees, 5 talks, one BoF and two E-ALE tutorial sessions.
In this blog post, we would like to highlight a number of talks from the conference that we found interesting. Each Bootlin engineer who attended the conference has selected one talk, and gives his/her feedback about this talk.
Device Tree BoF – Frank Rowand
Talk selected by Michael Opdenacker
The Device Tree BoF (Birds of a Feather session, which means an informal session about a technical topic, allowing participants to openly share questions and information) has been part of Embedded Linux Conferences for at least 2 or 3 years. For me, it has always been a good source of updates about the topic.
Frank started by sharing details about the Device Tree Workshop held in October in Prague, a one day meet-up and workshop for Device Tree contributors (like Maxime Ripard and Thomas Petazzoni from Bootlin who were invited), to address issues and plan for the next months. Slides and notes can be found on elinux.org.
Frank then went on by mentioning utilities, such as:
scripts/dtc/dt_to_config. It is not very new in the mainline kernel, but useful to generate a kernel configuration suitable for the devices present on your platform, in case you didn’t know this tool exists.
There’s an upcoming patch adding options to dtc (--annotate --full) to keep track of the line numbers in the device tree sources. This helps to locate in which DT source file a given property value comes from. The patch was idle for some time but Julia Lawall volunteered to take care of it. Thanks to her updates, this feature should be accepted in mainline soon.
The device tree compiler in mainline has also been augmented with further build checks. You can now use them by adding W=1 to make dtb. Here is an example for the Beagle Bone Black dtb:
make W=1 am335x-boneblack.dtb
arch/arm/boot/dts/am335x-boneblack.dtb: Warning (unit_address_vs_reg): Node /ocp/i2c@44e0b000/tda19988 has a reg or ranges property, but no unit name
arch/arm/boot/dts/am335x-boneblack.dtb: Warning (unit_address_vs_reg): Node /ocp/i2c@44e0b000/tda19988/ports/port@0 has a unit name, but no reg property
arch/arm/boot/dts/am335x-boneblack.dtb: Warning (unit_address_vs_reg): Node /ocp/i2c@44e0b000/tda19988/ports/port@0/endpoint@0 has a unit name, but no reg property
arch/arm/boot/dts/am335x-boneblack.dtb: Warning (unit_address_vs_reg): Node /ocp/ethernet@4a100000/slave@4a100200 has a unit name, but no reg property
arch/arm/boot/dts/am335x-boneblack.dtb: Warning (unit_address_vs_reg): Node /ocp/ethernet@4a100000/slave@4a100300 has a unit name, but no reg property
arch/arm/boot/dts/am335x-boneblack.dtb: Warning (unit_address_vs_reg): Node /ocp/lcdc@4830e000/port/endpoint@0 has a unit name, but no reg property
arch/arm/boot/dts/am335x-boneblack.dtb: Warning (simple_bus_reg): Node /ocp/l4_wkup@44c00000/prcm@200000/clocks missing or empty reg/ranges property
arch/arm/boot/dts/am335x-boneblack.dtb: Warning (simple_bus_reg): Node /ocp/l4_wkup@44c00000/prcm@200000/clockdomains missing or empty reg/ranges property
arch/arm/boot/dts/am335x-boneblack.dtb: Warning (simple_bus_reg): Node /ocp/l4_wkup@44c00000/scm@210000/scm_conf@0/clocks missing or empty reg/ranges property
arch/arm/boot/dts/am335x-boneblack.dtb: Warning (simple_bus_reg): Node /ocp/l4_wkup@44c00000/scm@210000/clockdomains missing or empty reg/ranges property
As far as I am concerned, the most interesting news remained the one that since Linux 4.15, device tree overlays are now easier to code. You no longer have to define weird “fragment” elements. You can now directly write normal nodes and use labels. The syntax is now exactly the same as for regular device tree sources!
For more details, grab the slides and if you event want to follow the discussions that happened that day, watch the video.
Tutorial: Introduction to Reverse Engineering – Mike Anderson
Talk selected by Quentin Schulz
Mike presented in an unusual 2-hour-long slot the different techniques to reverse-engineer things and the different reasons why you’d do so. After a mandatory disclaimer that reverse engineering may be illegal in some regions of the world, he introduced the different tools that anyone aspiring to reverse engineer should possess: from the obvious logic analyzer, multimeter, screwdrivers to the surprising heat gun. He then gave the first and very important step of the reverse engineering process: gathering information about the product by looking for patents, the FCC registration, manufacturer as well as carefully opening its case to examine the different components (maybe with the help of a microscope).
Later, Mike gave the multiple ways to retrieve the firmwares from the product, from the soldering of a JTAG interface to the downloading from the official website. He then offered some tools that can be used to dive into binaries and start the guessing game, and he finished his talk with an example of a reverse engineering of a protocol which required a lot of guessing and social reverse engineering.
Mike’s talk was pleasant to attend because of the high-level presentation of how to do reverse engineering while giving a quick real-life example.
Graphics Performance Analysis with FrameRetrace: A Responsive UI for ApiTrace – Mark Janes, Intel
Talk selected by Boris Brezillon
I first heard of FrameRetrace when Eric Anholt asked us to add support for the VC4 GPU to this tool, and my experience with it had been rather frustrating in that I was mainly struggling to make it work on a not yet supported architecture instead of being a simple user. So, when I saw that Mark was giving a talk on FrameRetrace usefulness and how to use it, I figured I couldn’t miss it. Well, those who looked carefuly at the schedule know I couldn’t attend it because I was giving my talk at the same time, but I did see it at FOSDEM a month before, and I’m pretty sure not much has changed since then.
Mark first described the GPU debugging/perf-anlysis tools ecosystem, saying that each GPU vendor has its own proprietary tools which most of the time are only supported on Windows. FrameRetrace is an attempt at providing a tool that exposes similar features while being open-source, cross-platform, and easily extensible to new hardware. This project is actually based on an exisiting project called ApiTrace, which it uses to capture OpenGL traces. The new feature that is interesting in FrameRetrace is that you can select the frame you want to replay, get all the hardware perf counters exposed by the GPU for this specific rendering job in order to figure out what is going wrong and then play with the OpenGL code to see how you can make things better and replay the rendering job with your local modification to see if it actually solves the problem.
I must admit I was really impressed by the demo, and now I understand why Eric (and others in the community) would like to have their GPU properly supported in FrameRetrace. It really looks like the kind of tool you don’t know you need until you’ve tested it, but once you do, you can’t do without it.
The Salmon Diet: Up-Streaming Drivers as a Form of Optimization – Gilad Ben-Yossef
Talk selected by Miquèl Raynal
Gilad was hired about a year ago to become the maintainer of the ARM® TrustZone® CryptoCell® device driver. Until now this driver was out of tree until it has been decided to upstream it. Here starts Gilad’s story.
It appeared that the right way to make it upstream was to go through the staging tree and the whole process around it. It was the first time for him to do it that way, that is why he felt it was interesting to share his experience.
At the beginning of his talk, he recalls that the driver was actually working, people already relied on it. Plus, it was released under the GPL. While all of this could make you think it was clean enough, Gilad realized that people who wrote it actually did not think about upstreaming and almost every patch to clean that driver removed more lines than it added, shrinking step by step the driver until 30% of the lines were removed!
Of course, removing the existing hardware abstraction macros was something to do, as well as running and correcting the whole checkpatch.pl output, but there are plenty of other good habits that one can adapt to his own situation, explained and well illustrated all along this talk.
Measuring and Summarizing Latencies using the Trace Event Subsystem – Tom Zanussi
Talk selected by Maxime Chevallier
Having some experience dealing with RT topics on Linux, I was looking forward to seeing Tom’s talk about these tracing features.
He gave really good examples on how to use the existing ‘latency histogram’ traces to get a cyclictest-like metric of wakeup latencies by measuring the time between sched_waking and sched_switch, and explaining how this could be re-used for other measurements such as network latencies.
What he presented was more than just having a trace in a buffer when a function is called. The tracing subsystem allows the use of handlers to perform actions when an event occurs. As an example, he demonstrated how to use the onmax handler to accumulate the maximum wakeup latency observed, each time saving crucial pieces of information on the execution context.
He then went on to describe the next-level features that are being merged, namely function events by Steven Rostedt, and Inter events by Tom himself. They allow the user to use any of the kernel functions as tracepoints, and build complex events and traces to pinpoint really specific sequences.
I recommend to read this LWN article on inter-event tracing, and of course have a look at Tom’s talk and slides.
Steering Xenomai into the Real-Time Linux Future – Jan Kiszka
Talk selected by Thomas Petazzoni
In this talk, long-term Xenomai developer and Siemens engineer Jan Kiszka gave a very interesting status of the Xenomai project and its roadmap. He started by refreshing the audience about what Xenomai is: an RTOS-to-Linux portability framework. It comes in two flavors: a co-kernel extension for a patched Linux kernel, and as libraries running for native Linux (including PREEMPT_RT). He then went on to compare the respective advantages and drawbacks of the two flavors, citing accurate modeling of legacy RTOS behavior and strong separation of real-time vs. non real-time code as the key advantages of the co-kernel approach.
Jan then summarized the history of Xenomai, from the early days as a sub-project of RTAI to the current status of Xenomai 3.0, released in 2015 after more than 5 years of development. However, even though Xenomai is widely used in the industry, its development relies on just a few individuals. Siemens is a heavy user of Xenomai, and in 2017, they started a discussion: should they migrate away from Xenomai or invest into it. Siemens made the decision to invest in the project. The same year, Xenomai main developer Philippe Gerum published an e-mail RTnet, Analogy and the elephant in the room also calling for help to maintain some parts of Xenomai.
Following those discussions, some changes were decided in the Xenomai project: Philippe Gerum will step back from the project lead, and Jan Kiszka will take over his role.
Regarding the I-Pipe kernel patch (which allows to support the co-kernel approach), the Xenomai project will discontinue a number of architectures (nios2, SH, Blackfin, PPC64, ARM < v7) and will only maintain patches for the latest Linux kernel LTS, in order to reduce the maintenance effort.
Jan announced that Xenomai 3.0.7 is soon to be released, that Xenomai 3.1 will introduce ARM64 support, and that Xenomai 2 is unmaintained and therefore users should migrate to Xenomai 3. He also gave a status on the driver stacks, citing that RTnet needs more love, and that Analogy is orphaned and needs a new maintainer.
Towards the end of his talk, Jan then started discussing the more distant future of Xenomai. The future version of Xenomai has the goal of improving the integration of the co-kernel approach, to simplify maintenance and possibly provide a chance to be upstreamed in Linux. This new approach will be split in two elements, called Dovetail (interrupt routing, co-kernel hooks) and Steely (co-kernel implementation). He made it clear that this is currently not production-ready at all. He noted that this new implementation allows a significant reduction of the code base, about 50% smaller than the current implementation. The code is already available in two Git repositories: Dovetail and Steely.
All in all, Jan’s talk was a very interesting one, providing a good coverage of Xenomai’s status and future. The video of his talk is definitely worth watching, and the slides are also available.
An Introduction to Asymmetric Multiprocessing: When this Architecture can be a Game Changer and How to Survive It – Nicola La Gloria & Laura Nao
Talk selected by Mylène Josserand
In this talk, Nicola La Gloria and Laura Nao from Kynetics presented how to handle communication between a micro-controller running bare metal code and a CPU with a full OS (such as GNU/Linux or Android).
They showed the different approaches for communication (supervised or not supervised: i.e. CPU and MCU can communicate using an hypervisor or directly) and presented the Inter-Processing Communication.
After this introduction, Laura told us about their use-case, running on an NXP i.MX7, which comprises a Cortex-M4 micro-controller and a Cortex-A7 processor: the MCU retrieves data from a sensor, which will be displayed by the CPU.
She gave feedback on how they implemented this communication and the different mechanisms used (Message Unit, RPMsg, RDC, kexec/kdump, etc). The explanation of the different mechanisms was really interesting, and particularly relevant for those who had never heard about them.
They did a short tutorial and gave some tips that would definitely be appreciated by people who start this kind of project. And finally, they did a demonstration of all the work they have done.
So if you are interested in the subject or even only for your general knowledge, have a look at their talk (video and slides).
System-in-Package Technology: Making it Easier to Build Your Own Linux Computer – Erik Welsh & Jason Kridner
Talk selected by Alexandre Belloni
Eric Welsh started to talk about how software influences hardware design and why open source hardware matters. He then presented the System-in-Package technology and in particular the Octavo OSD3358. It includes a TI AAM335x SoC, DDR3 SDRAM, a PMIC and all the related power circuitry, components which are always required. This allows the hardware engineers to concentrate on the added value of the final product.
Great pictures and videos of the SiP internals and its manufacturing process were shown.
Jason then came on stage to present the OSD3358 integration on the PocketBeagle.
Eric finally explained how easy it is to assemble the OSD3358 on a PCB, even by hand with a video to prove it. He finally concluded by summing up the benefits of using a SiP: easy bring-up, lower cost of PCB, easy manufacturing and migration from SBC prototyping to custom PCB.
It was quite enlightening for software engineers as it showed the hardware internals with some great details.
Have a look at the video and slides.
In conclusion, this was again a really nice opportunity to share and acquire knowledge from other engineers deeply involved in the Open Source community, as well as meeting people that we sometimes know only by their name on a mailing list. Next year this event will happen in Monterey Bay, California (March 19 – 21, 2019). See you there!
While this week’s goal was set to supporting dmabuf in our Sunxi-Cedrus VAAPI implementation with GStreamer, progress was made on GStreamer support alone. The first milestone was displaying the video from videotestsrc, which produces a sample test output, to kmssink, which handles video output directly with DRM planes.
On the VAAPI side, things are more complicated and a number of different areas of the sunxi-cedrus VAAPI backend had to be reworked. For instance, the slices constituting MPEG2 frames are not submitted in the same way by VLC and GStreamer. Buffers management is also done slightly differently between these two users of libVA. The net result is that a segmentation fault caused by a memory management mishaps is occurring with GStreamer and is still being investigated.
This week was also the occasion to dig into the partial reference code that Allwinner published in 2015 (to grasp a better understanding of the MPEG2 decoding process with the VPU) and start updating the register documentation on the linux-sunxi wiki, where some fields documented by the reference code were still marked as unknown. The Sunxi-Cedrus page was also updated to reflect the current status and effort. These resources will get updated as development happens. More precisely, we’d like to provide instructions to deploy this work, once it has reached a decent level of usability. Stay tuned for our next update!
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.
Following up on the work started last week, I finished implementing initial support for displaying the NV12-based tiled format (that we shall call MB32-tiled NV12). The frame, that was dumped from the VPU, is now correctly displayed on the screen (after adapting scaling coefficients that needed specific tweaking for this use case).
The result can be shown in the following picture, where our Big Buck Bunny has the right coloring:
Scaling is also supported for the tiled format, so the frame can be shown in full screen without resorting to software scaling.
A series of patches supporting these features was sent for review on the dri-devel mailing list, where it already got some feedback from Maxime Ripard (who maintains the sun4i DRM driver impacted by these patches) as well as other members of the community! There is already enough material to craft a second version and send it again for review.
Significant time was spent figuring out the DRM, KMS, DRI and X11 graphics pipeline (as well as specific details of the inner workings of display hardware) and how to properly integrate the overlay DRM plane with all this. We are evaluating all our options here before spending time on a specific implementation. Of course, we are trying to keep things as generic as possible and avoid introducing platform-specific code in userspace, but there are also challenges to overcome in this regard. On the Wayland side, things are looking much brighter as compositors such as Weston have support for managing hardware planes directly, so there should be less work required.
Finally, I started working on dmabuf support, that I am testing with gstreamer‘s kmssink, that allows outputting directly in a hardware plane. Once this work is ready, we’ll be able to get an idea of the performance of the VPU when it is not limited by software-based untiling and compositing. Stay tuned for updates in this direction!