Bootlin at the Embedded Linux Conference 2018

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).

Embedded Linux Conference 2018

We will also be giving a number of talks, tutorials or moderating Bird of a Feather sessions:

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.

Crowdfunding campaign for upstream Linux kernel driver for Allwinner VPU

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!

Back from ELCE: participation to the Device Tree workshop

After publishing our slides and videos from the Embedded Linux Conference Europe (ELCE), reporting on talks selected by Free Electrons engineers, and mentioning the award given to Michael Opdenacker, here comes the last blog post giving feedback from our participation to the 2017 edition of this conference.

On Thursday after ELCE, Free Electrons engineers Maxime Ripard and Thomas Petazzoni participated to the Device Tree workshop, a day-long meeting to discuss the status and future of Device Tree support, especially in the context of the Linux kernel.

Device Tree Workshoup group photo 2017

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.

MIPI I3C specification published, and new iteration of Linux I3C subsystem

MIPI I3C specification publishedBack 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.

Free Electrons contributes Linux support for Microsemi MIPS SoC

VSC7513 Block Diagram
Microsemi VSC7513 Block Diagram
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.

Back from ELCE: award to Free Electrons CEO Michael Opdenacker

The Embedded Linux Conference Europe 2017 took place at the end of October in Prague. We already posted about this event by sharing the slides and videos of Free Electrons talks and later by sharing our selection of talks given by other speakers.

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.

Michael Opdenacker receives an award at the Embedded Linux Conference Europe

Free Electrons is proud to see its continuous commitment to knowledge sharing and community participation be recognized by this award!

Linux 4.14 released, Free Electrons contributions

Penguin from Mylène Josserand
Drawing from Mylène Josserand,
based on a picture from Samuel Blanc under CC-BY-SA
Linux 4.14, which is going to become the next Long Term Supported version, has been released a week ago by Linus Torvalds. As usual, LWN.net did an interesting coverage of this release cycle merge window, highlighting the most important changes: The first half of the 4.14 merge window and The rest of the 4.14 merge window.

According to Linux Kernel Patch statistics, Free Electrons contributed 111 patches to this release, making it the 24th contributing company by number of commits: a somewhat lower than usual contribution level from our side. At least, Free Electrons cannot be blamed for trying to push more code into 4.14 because of its Long Term Support nature! 🙂

The main highlights of our contributions are:

  • On the RTC subsystem, Alexandre Belloni made as usual a number of fixes and improvements to various drivers, especially the ds1307 driver.
  • On the NAND subsystem, Boris Brezillon did a number of small improvements in various areas.
  • On the support for Marvell platforms
    • Antoine Ténart improved the ppv2 network driver used by the Marvell Armada 7K/8K SoCs: support for 10G speed and TSO support are the main highlights. In order to support 10G speed, Antoine added a driver in drivers/phy/ to configure the common PHYs in the Armada 7K/8K SoCs.
    • Thomas Petazzoni also improved the ppv2 network driver by adding support for TX interrupts and per-CPU RX interrupts.
    • Grégory Clement contributed some patches to enable NAND support on Armada 7K/8K, as well as a number of fixes in different areas (GPIO fix, clock handling fixes, etc.)
    • Miquèl Raynal contributed a fix for the Armada 3700 SPI controller driver.
  • On the support for Allwinner platforms
    • Maxime Ripard contributed the support for a new board, the BananaPI M2-Magic. Maxime also contributed a few fixes to the Allwinner DRM driver, and a few other misc fixes (clock, MMC, RTC, etc.).
    • Quentin Schulz contributed the support for the power button functionality of the AXP221 (PMIC used in several Allwinner platforms)
  • On the support for Atmel platforms, Quentin Schulz improved the clock drivers for this platform to properly support the Audio PLL, which allowed to fix the Atmel audio drivers. He also fixed suspend/resume support in the Atmel MMC driver to support the deep sleep mode of the SAMA5D2 processor.

In addition to making direct contributions, Free Electrons is also involved in the Linux kernel development by having a number of its engineers act as Linux kernel maintainers. As part of this effort, Free Electrons engineers have reviewed, merged and sent pull requests for a large number of contributions from other developers:

  • Boris Brezillon, as the NAND subsystem maintainer and MTD subsystem co-maintainer, merged 68 patches from other developers.
  • Alexandre Belloni, as the RTC subsystem maintainer and Atmel ARM platform co-maintainer, merged 32 patches from other developers.
  • Grégory Clement, as the Marvell ARM platform co-maintainer, merged 29 patches from other developers.
  • Maxime Ripard, as the Allwinner ARM platform co-maintainer, merged 18 patches from other developers.

This flow of patches from kernel maintainers to other kernel maintainers is also nicely described for the 4.14 release by the Patch flow into the mainline for 4.14 LWN.net article.

The detailed list of our contributions:

Back from ELCE: selection of talks from the Free Electrons team

As discussed in our previous blog post, Free Electrons had a strong presence at the Embedded Linux Conference Europe, with 7 attendees, 4 talks, one BoF and one poster during the technical show case.

In this blog post, we would like to highlight a number of talks from the conference that we found interesting. Each Free Electrons engineer who attended the conference has selected one talk, and gives his/her feedback about this talk.

uClibc Today: Still Makes Sense – Alexey Brodkin

Talk selected by Michael Opdenacker

uClibc Today: Still Makes Sense – Alexey BrodkinAlexey Brodkin, an active contributor to the uClibc library, shared recent updates about this C library, trying to show people that the project was still active and making progress, after a few years during which it appeared to be stalled. Alexey works for Synopsys, the makers of the ARC architecture, which uClibc supports.

If you look at the repository for uClibc releases, you will see that since version 1.0.0 released in 2015, the project has made 26 releases according to a predictable schedule. The project also runs runtime regression tests on all its releases, which weren’t done before. The developers have also added support for 4 new architectures (arm64 in particular), and uClibc remains the default C library that Buildroot proposes.

Alexey highlighted that in spite of the competition from the musl library, which causes several projects to switch from uClibc to musl, uClibc still makes a lot of sense today. As a matter of fact, it supports more hardware architectures than glibc and musl do, as it’s the only one to support platforms without an MMU (such as noMMU ARM, Blackfin, m68k, Xtensa) and as the library size is still smaller that what you get with musl (though a static hello_world program is much smaller with musl if you have a close look at the library comparison tests he mentioned).

Alexey noted that the uClibc++ project is still alive too, and used in OpenWRT/Lede by default.

Read the slides and watch the video of his talk.

Identifying and Supporting “X-Compatible” hardware blocks – Chen-Yu Tsai

Talk selected by Quentin Schulz

Identifying and Supporting “X-Compatible” hardware blocks – Chen-Yu TsaiAn SoC is made of multiple IP blocks from different vendors. In some cases the source or model of the hardware blocks are neither documented nor marketed by the SoC vendor. However, since there are only very few vendors of a given IP block, stakes are high that your SoC vendor’s undocumented IP block is compatible with a known one.

With his experience in developing drivers for multiple IP blocks present in Allwinner SoCs and as a maintainer of those same SoCs, Chen-Yu first explained that SoC vendors often either embed some vendors’ licensed IP blocks in their SoCs and add the glue around it for platform- or SoC-specific hardware (clocks, resets and control signals), or they clone IP blocks with the same logic but some twists (missing, obfuscated or rearranged registers).

To identify the IP block, we can dig into the datasheet or the vendor BSP and compare those with well documented datasheets such as the one for NXP i.MX6, TI KeyStone II or the Zynq UltraScale+ MPSoC, or with mainline drivers. Asking the community is also a good idea as someone might have encountered an IP with the same behaviour before and can help us identify it quicker.

Some good identifiers for IPs could be register layouts or names along with DMA logic and descriptor format. For the unlucky ones that have been provided only a blob, they can look for the symbols in it and that may slightly help in the process.

He also mentioned that identifying an IP block is often the result of the developer’s experience in identifying IPs and other time just pure luck. Unfortunately, there are times when someone couldn’t identify the IP and wrote a complete driver just to be told by someone else in the community that this IP reminds him of that IP in which case the work done can be just thrown away. That’s where the community plays a strong role, to help us in our quest to identify an IP.

Chen-Yu then went on with the presentation of the different ways to handle the multiple variants of an IP blocks in drivers. He said that the core logic of all IP drivers is usually presented as a library and that the different variants have a driver with their own resources, extra setup and use this library. Also, a good practice is to use booleans to select features of IP blocks instead of using the ID of each variant.
For IPs whose registers have been altered, the way to go is usually to write a table for the register offsets, or use regmaps when bitfields are also modified. When the IP block differs a bit too much, custom callbacks should be used.

He ended his talk with his return from experience on multiple IP blocks (UART, USB OTG, GMAC, EMAC and HDMI) present in Allwinner SoCs and the differences developers had to handle when adding support for them.

Read the slides and watch the video of his talk.

printk(): The Most Useful Tool is Now Showing its Age – Steven Rostedt & Sergey Senozhatsky

Talks selected by Boris Brezillon. Boris also covered the related talk “printk: It’s Old, What Can We Do to Make It Young Again?” from the same speakers.

printk(): The Most Useful Tool is Now Showing its Age – Steven Rostedt & Sergey SenozhatskyMaybe I should be ashamed of saying that but printk() is one of the basic tool I’m using to debug kernel code, and I must say it did the job so far, so when I saw these presentations talking about how to improve printk() I was a bit curious. What could be wrong in printk() implementation?
Before attending the talks, I never digged into printk()’s code, because it just worked for me, but what I thought was a simple piece of code appeared to be a complex infrastructure with locking scheme that makes you realize how hard it is when several CPUs are involved.

At its core, printk() is supposed to store logs into a circular buffer and push new entries to one or several consoles. In his first talk Steven Rostedt walked through the history of printk() and explained why it became more complex when support for multi CPU appeared. He also detailed why printk() is not re-entrant and the problem it causes when called from an NMI handler. He finally went through some fixes that made the situation a bit better and advertised the 2nd half of the talk driven by Sergey Senozhatsky.

Note that between these two presentations, the printk() rework has been discussed at Kernel Summit, so Sergey already had some feedback on his proposals. While Steven presentation focused mainly on the main printk() function, Sergey gave a bit more details on why printk() can deadlock, and one of the reasons why preventing deadlocks is so complicated is that printk() delegates the ‘print to console’ aspect to console drivers which have their own locking scheme. To address that, it is proposed to move away from the callback approach and let console drivers poll for new entries in the console buffer instead, which would remove part of the locking issues. The problem with this approach is that it brings even more uncertainty on when the logs are printed on the consoles, and one of the nice things about printk() in its current form is that you are likely to have the log printed on the output before printk() returns (which helps a lot when you debug things).

He also mentioned other solutions to address other possible deadlocks, but I must admit I got lost at some point, so if you’re interested in this topic I recommend that you watch the video (printk(): The Most Useful Tool is Now Showing its Age, sadly no video is available for the second talk) and read the slides (printk(): The Most Useful Tool is Now Showing its Age and printk: It’s Old, What Can We Do to Make It Young Again?).

More robust I2C designs with a new fault-injection driver – Wolfram Sang

Talk selected by Miquèl Raynal

More robust I2C designs with a new fault-injection driver – Wolfram SangAlthough Wolfram had a lot of troubles starting its presentation lacking a proper HDMI adaptater, he gave an illuminating talk about how, as an I2C subsystem maintainer, he would like to strengthen the robustness of I2C drivers.

He first explained some basics of the I2C bus like START and STOP conditions and introduced us to a few errors he regularly spots in drivers. For instance, some badly written drivers used a START and STOP sequence while a “repeated START” was needed. This is very bad because another master on the bus could, in this little spare idle delay, decide to grab the medium and send its message. Then the message right after the repeated START would not have the expected effect. Of course plenty other errors can happen: stalled bus (SDA or SCL stuck low), lost arbitration, faulty bits… All these situations are usually due to incorrect sequences sent by the driver.

To avoid so much pain debugging obscure situations where this happens, he decided to use an extended I2C-gpio interface to access SDA and SCL from two external GPIOs and this way forces faulty situations by simply pinning high or low one line (or both) and see how the driver reacts. The I2C specification and framework provide everything to get out of a faulty situation, it is just a matter of using it (sending a STOP condition, clocking 9 times, operate a reset, etc).

Wolfram is aware of his quite conservative approach but he is really scared about breaking users by using random quirks so he tried with this talk to explain his point of view and the solutions he wants to promote.

Two questions that you might have a hard time hearing were also interesting. The first person asked if he ever considered using a “default faulty chip” designed to do by itself this kind of fault injection and see how the host reacts and behaves. Wolfram said buying hardware is too much effort for debugging, so he was more motivated to get something very easy and straightforward to use. Someone else asked if he thought about multiple clients situation, but from Wolfram’s point of view, all clients are in the same state whether the bus is busy or free and should not badly behave if we clock 9 times.

Watch the video and grab the slides.

HDMI 4k Video: Lessons Learned – Hans Verkuil

Talk selected by Maxime Ripard

HDMI 4k Video: Lessons Learned – Hans VerkuilHaving worked recently on a number of display related drivers, it was quite natural to go see what I was probably going to work on in a quite close future.

Hans started by talking about HDMI in general, and the various signals that could go through it. He then went on with what was basically a war story about all the mistakes, gotchas and misconceptions that he encountered while working on a video-conference box for Cisco. He covered the hardware itself, but also more low-level oriented aspects, such as the clocks frequencies needed to operate properly, the various signals you could look at for debugging or the issues that might come with the associated encoding and / or color spaces, especially when you want to support as many displays as you can. He also pointed out the flaws in the specifications that might lead to implementation inconsistencies. He concluded with the flaws of various HDMI adapters, the issues that might arise using them on various OSes, and how to work around them when doable.

Watch the video and the slides.

The Serial Device Bus – Johan Hovold

Talk selected by Thomas Petazzoni

The Serial Device Bus – Johan HovoldJohan started his talk at ELCE by exposing the problem with how serial ports (UARTs) are currently handled in the Linux kernel. Serial ports are handled by the TTY layer, which allows user-space applications to send and receive data with what is connected on the other side of the UART. However, the kernel doesn’t provide a good mechanism to model the device that is connected at the other side of the UART, such as a Bluetooth chip. Due to this, people have resorted to either writing user-space drivers for such devices (which falls short when those devices need additional resources such as regulators, GPIOs, etc.) or to developing specific TTY line-discipline in the kernel. The latter also doesn’t work very well because a line discipline needs to be explicitly attached to a UART to operate, which requires a user-space program such as hciattach used in Bluetooth applications.

In order to address this problem, Johan picked up the work initially started by Rob Herring (Linaro), which consisted in writing a serial device bus (serdev in short), which consists in turning UART into a proper bus, with bus controllers (UART controllers) and devices connected to this bus, very much like other busses in the Linux kernel (I2C, SPI, etc.). serdev was initially merged in Linux 4.11, with some improvements being merged in follow-up versions. Johan then described in details how serdev works. First, there is a TTY port controller, which instead of registering the traditional TTY character device will register the serdev controller and its slave devices. Thanks to this, one can described in its Device Tree child nodes of the UART controller node, which will be probed as serdev slaves. There is then a serdev API to allow the implementation of serdev slave drivers, that can send and receive data of the UART. Already a few drivers are using this API: hci_serdev, hci_bcm, hci_ll, hci_nokia (Bluetooth) and qca_uart (Ethernet).

We found this talk very interesting, as it clearly explained what is the use case for serdev and how it works, and it should become a very useful subsystem for many embedded applications that use UART-connected devices.

Watch the video and the slides.

GStreamer for Tiny Devices – Olivier Crête

Talk selected by Grégory Clement

GStreamer for Tiny Devices – Olivier CrêteThe purpose of this talk was to show how to shrink Gstreamer to make it fit in an embedded Linux device. First, Olivier Crête introduced what GStreamer is, it was very high level but well done. Then after presenting the issue, he showed step by step how he managed to reduce the footprint of a GStreamer application to fit in his device.

In a first part it was a focus on features specific to GStreamer such as how to generate only the needed plugins. Then most of the tricks showed could be used for any C or C++ application. The talk was pretty short so there was no useless or boring part Moreover, the speaker himself was good and dynamic.

To conclude it was a very pleasant talk teaching step by step how to reduce the footprint of an application being GStreamer or not.

Watch the video and the slides.

Back from Kernel Recipes: slides and videos

As we announced previously, we participated to the Embedded Recipes and Kernel Recipes conferences in September in Paris. Three people from Free Electrons attended the event: Free Electrons CEO Michael Opdenacker, and Free Electrons engineers Mylène Josserand and Maxime Ripard.

Introduction to Yocto Project / OpenEmbedded, by Mylène Josserand

Mylène Josserand gave an Introduction to the Yocto Project / OpenEmbedded-core. The slides are available in PDF or as LaTeX code.

An introduction to the Linux DRM subsystem, by Maxime Ripard

Maxime Ripard gave an Introduction to the Linux DRM subsystem. The slides are available in PDF or as LaTeX code.

Other videos and slides

The slides of all talks are available on the Embedded Recipes and Kernel Recipes conference websites. Youtube playlists are available for Embedded Recipes 2017 and Kernel Recipes 2017 as well.

Conclusion

With its special one track format, an attendance limited to 100 people, excellent choice of talks and nice social events, Kernel Recipes remains a very good conference that we really enjoyed. Embedded Recipes, which was in its first edition this year, followed the same principle, with the same success. We’re looking forward to attending next year editions, and hopefully contributing a few talks as well. See you all at Embedded and Kernel Recipes in 2018!

Back from ELCE 2017: slides and videos

Free Electrons participated to the Embedded Linux Conference Europe last week in Prague. With 7 engineers attending, 4 talks, one BoF and a poster at the technical showcase, we had a strong presence to this major conference of the embedded Linux ecosystem. All of us had a great time at this event, attending interesting talks and meeting numerous open-source developers.

Free Electrons team at the Embedded Linux Conference Europe 2017
Free Electrons team at the Embedded Linux Conference Europe 2017. Top, from left to right: Maxime Ripard, Grégory Clement, Boris Brezillon, Quentin Schulz. Bottom, from left to right: Miquèl Raynal, Thomas Petazzoni, Michael Opdenacker.

In this first blog post about ELCE, we want to share the slides and videos of the talks we have given during the conference.

SD/eMMC: New Speed Modes and Their Support in Linux – Gregory Clement

Grégory ClementSince the introduction of the original “default”(DS) and “high speed”(HS) modes, the SD card standard has evolved by introducing new speed modes, such as SDR12, SDR25, SDR50, SDR104, etc. The same happened to the eMMC standard, with the introduction of new high speed modes named DDR52, HS200, HS400, etc. The Linux kernel has obviously evolved to support these new speed modes, both in the MMC core and through the addition of new drivers.

This talk will start by introducing the SD and eMMC standards and how they work at the hardware level, with a specific focus on the new speed modes. With this hardware background in place, we will then detail how these standards are supported by Linux, see what is still missing, and what we can expect to see in the future.

Slides [PDF], Slides [LaTeX source]

An Overview of the Linux Kernel Crypto Subsystem – Boris Brezillon

Boris BrezillonThe Linux kernel has long provided cryptographic support for in-kernel users (like the network or storage stacks) and has been pushed to open these cryptographic capabilities to user-space along the way.

But what is exactly inside this subsystem, and how can it be used by kernel users? What is the official userspace interface exposing these features and what are non-upstream alternatives? When should we use a HW engine compared to a purely software based implementation? What’s inside a crypto engine driver and what precautions should be taken when developing one?

These are some of the questions we’ll answer throughout this talk, after having given a short introduction to cryptographic algorithms.

Slides [PDF], Slides [LaTeX source]

Buildroot: What’s New? – Thomas Petazzoni

Thomas PetazzoniBuildroot 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.

Since our last “What’s new” talk at ELC 2014, three and half years have passed, and Buildroot has continued to evolve significantly.

After a short introduction about Buildroot, this talk will go through the numerous new features and improvements that have appeared over the last years, and show how they can be useful for developers, users and contributors.

Slides [PDF], Slides [LaTeX source]

Porting U-Boot and Linux on New ARM Boards: A Step-by-Step Guide – Quentin Schulz

May it be because of a lack of documentation or because we don’t know where to look or where to start, it is not always easy to get started with U-Boot or Linux, and know how to port them to a new ARM platform.

Based on experience porting modern versions of U-Boot and Linux on a custom Freescale/NXP i.MX6 platform, this talk will offer a step-by-step guide through the porting process. From board files to Device Trees, through Kconfig, device model, defconfigs, and tips and tricks, join this talk to discover how to get U-Boot and Linux up and running on your brand new ARM platform!

Slides [PDF], Slides [LaTeX source]

BoF: Embedded Linux Size – Michael Opdenacker

This “Birds of a Feather” session will start by a quick update on available resources and recent efforts to reduce the size of the Linux kernel and the filesystem it uses.

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!

Slides [PDF], Slides [LaTeX source]