Tag: contribution

2014 Q3 newsletter

Bootlin is happy to share some news about the latest training and contribution activities of the company.

Kernel contributions

Since our last newsletter, our engineering team continued to make significant contributions to the Linux kernel, especially in the area of supporting ARM processors and platforms:

  • 218 patches from Bootlin were merged into Linux 3.15, making Bootlin the 12th contributing company for this release by number of patches. See our blog post.
  • 388 patches from Bootlin were merged into Linux 3.16, making Bootlin the 7th contributing company for this release, by number of patches. See our blog post.
  • For the upcoming 3.17 release, we already have 146 patches merged, and we have a lot more work being done for future kernel releases.

The major areas of our contributions were:

  • The addition of an ubiblk driver, which allows traditional block filesystems to be used on top of UBI devices, and therefore on NAND flash storage. Only read-only support is available, but it already allows to make use of the super efficient SquashFS filesystem on top of NAND flash in a safe way.
  • Another major addition is support for the new Marvell Armada 375 and Armada 38x processors. In just two releases (3.15 and 3.16) we almost pushed entire support for these new processors. The network driver for Armada 375 is one missing piece, coming in 3.17.
  • Our maintenance work on the Atmel AT91 and SAMA5 processors has continued, with more conversion to the Device Tree, the common clock framework, and other modern kernel mechanisms. We have also developed the DRM/KMS (graphics) driver for the SAMA5D3 SoC, which has already been posted and should hopefully be merged soon.
  • Our work to support the Marvell Berlin processor has started to be merged in 3.16. This processor is used in various TVs, set-top boxes or devices like the Google Chromecast. Basic support was merged including Device Trees, clock drivers, pin-muxing driver, GPIO and SDHCI support. AHCI support will be in 3.17, and USB and network support should be in 3.18.
  • Additional work was done on support for Allwinner ARM SoCs, especially the A31 processor: SPI and I2C support, drivers for the P2WI bus and the PRCM controller, and support for USB.

We now have broad experience in writing kernel drivers and getting code merged into the mainline tree. Do not hesitate to contact us if you need help to develop Linux kernel drivers, or to support a new board or processor.

Buildroot contributions

Our involvement into the Buildroot project, a popular embedded Linux build system, is going on. We have merged 159 patches in the 2014.05 release of the project (total of 1293 patches), and 129 patches in the 2014.08 release of the project (total of 1353 patches). Moreover, our engineer Thomas Petazzoni is regularly an interim maintainer of the project, when the official maintainer Peter Korsgaard is not available. Some of the major features we contributed: major improvements to Python 3 support, addition of EFI bootloaders, addition of support for the Musl C library.

Regular embedded Linux projects

Of course, we also conducted embedded Linux development and boot time optimization projects for various embedded system makers, with less visible impact on community projects. However, we will try to share generic technical experience from such projects through future blog posts.

New training course: Yocto Project and OpenEmbedded

A large number of embedded Linux projects use embedded Linux build systems to integrate the various software components of the system into a working root filesystem image. Among the solutions available to achieve this, the Yocto Project and OpenEmbedded are very popular.

We have therefore launched a new 3 day Yocto Project and OpenEmbedded training course to help engineers and companies who are using, or are interested in using these solutions for their embedded Linux projects. Starting from the basics of understanding the core principles of Yocto, the training course goes into the details of writing package recipes, integrating support for a board into Yocto, creating custom images, and more.

The detailed agenda of the training course is available. You can order this training course at your location, or participate to the first public session organized on November 18-20 in France.

Embedded Linux training course updated

The embedded Linux ecosystem is evolving very quickly, and therefore we are continuously updating our training courses to match the latest developments. As part of this effort, we have recently conducted a major update to our Embedded Linux course: the hardware platform used for the practical labs has been changed to the popular and very interesting Atmel Xplained SAMA5D3, and many practical labs have been improved to provide a more useful learning experience. See our blog post for more details.

Mailing list for training participants

We have launched a new service for the participants to our training sessions: a mailing list dedicated to them, and through which they can ask additional questions after the course, share their experience, get in touch with other training participants and Bootlin engineers. Of course, all Bootlin engineers are on the mailing list and participate to the discussions. Another useful service offered by our training courses!

This resource is no longer available, but participants to our training sessions are still welcome to contact us by e-mail.

Conferences: ELC, ELCE, Kernel Recipes

The Bootlin engineering team will participate to the Embedded Linux Conference Europe and Linux Plumbers, next month in Düsseldorf, Germany. Several Bootlin engineers will also be giving talks during ELCE:

In addition, Thomas will participate to the Buildroot Developers Day, taking place right before the Embedded Linux Conference Europe in Düsseldorf.

See also our blog post about ELCE for more details.

Maxime Ripard and Michael Opdenacker will participate to the Kernel Recipes 2014 conference, on September 25-26 in Paris. Maxime will be giving his Allwinner kernel talk at this conference. See our blog post for more details.

Last but not least, we have recently published the videos of a number of talks from the previous Embedded Linux Conference, held earlier this year in San Jose. A lot of interesting material about embedded Linux! Check out our blog post for more details.

Upcoming training sessions

We have a number of public training sessions dates, with seats available:

Sessions and dates

Linux 3.16 released, Bootlin 7th contributing company

Linus Torvalds has released the 3.16 kernel a few weeks ago. Unfortunately, the KernelNewbies LinuxChanges page has not been updated, but LWN.net summaries of the merge window (part 1, part 2 and final part) give a good summary of the important changes available in Linux 3.16.

On Bootlin’sside, 3.16 has been our most active kernel cycle ever: we have merged 388 patches in this cycle, making Bootlin the 7th company contributing to the Linux kernel by number of patches according to the statistics. Bootlin is ranked right after Texas Instruments, and before Novell, Renesas or Google. (Note that the statistics rank Bootlin as 9th, but this includes the “Unknown” and “Hobbyists” categories which are not companies). This strong participation clearly shows Bootlin’sability to get code merged in the mainline Linux kernel, as we’ve progressively done since kernel 3.6 over the last two years.

We are therefore available to help companies willing to add support for their hardware (processor, system-on-chip, module, or board) to the mainline Linux kernel. Do not hesitate to contact to get the discussion started.

Our major contributions have again been focused on the support of various ARM processor families:

  • On the Atmel SoC family
    • Conversion of the SAM9RL processor to the Device Tree. Done by Alexandre Belloni.
    • Huge cleanup of ADC/touchscreen handling: improvements in the IIO at91_adc driver to support more SoC families, and conversions of several Atmel platforms to use this driver, and then finally removal of the old atmel_tsadcc driver. Done by Alexandre Belloni.
    • Numerous fixes to the clock handling on various SoCs, following their conversion to the Common Clock Framework. Done by Alexandre Belloni.
    • Conversion of the SAM9RL, SAM9x5 and SAM9n12 SoCs to the Common Clock Framework. Done by Boris Brezillon.
    • Boris Brezillon is now one of the official maintainers for AT91 clock support.
  • On the Allwinner SoC family
    • Addition of PWM support to sun4i and sun7i. Done by Alexandre Belloni.
    • Addition of SMBus support to the regmap subsystem. This was needed to support the P2WI bus of Allwinner A31. Done by Boris Brezillon.
    • New I2C driver for the P2WI bus of Allwinner A31, used to communicate with the PMIC. Done by Boris Brezillon.
    • Improvements to the Allwinner pinctrl driver needed to support the P2WI bus. Done by Boris Brezillon.
    • Addition of a driver for the PRCM (Power, Reset and Clock Management) unit of the Allwinner A31. Done by Boris Brezillon.
    • Numerous cleanups of the pinctrl driver for Allwinner. Done by Maxime Ripard.
    • Addition of the ARM PMU description in the Device Tree of Allwinner platforms. Done by Maxime Ripard.
    • Add USB support for Allwinner A31. Done by Maxime Ripard, with some help from Boris Brezillon.
    • Various improvements to Allwinner clock drivers. Done by Maxime Ripard.
  • On the Marvell Berlin SoC family
    • Addition of basic Device Tree descriptions for several Marvell Berlin processors and boards. Done by Antoine Ténart.
    • Addition of clock drivers and DT clock descriptions of the Marvell Berlin processors. Done by Alexandre Belloni.
    • Addition of the pinctrl drivers for the Marvell Berlin processors. Done by Antoine Ténart.
    • Enabling of SDHCI and GPIO support on Marvell Berlin. Done by Antoine Ténart.
  • On the Marvell EBU SoC family
    • Addition of watchdog support for Armada 375 and Armada 38x, which required some changes to the existing watchdog driver. Done by Ezequiel Garcia.
    • Addition of thermal support for Armada 375 and Armada 38x, which required some changes in the existing armada_thermal driver. Done by Ezequiel Garcia.
    • Improvements of the pxa3xx_nand driver used for NAND support on Armada 370/375/38x/XP to use the newly introduced ECC strength and step size Device Tree bindings, which allows from the Device Tree to override the ECC constraints described by ONFI, when needed to match the bootloader constraints. Done by Ezequiel Garcia.
    • Addition of a generic software TSO (TCP Segmentation Offload) layer, and the corresponding changes to enable this feature in the mv643xx_eth and mvneta network drivers. This gives a huge performance boost in transmit operations! Done by Ezequiel Garcia.
    • SMP support for Armada 375 and Armada 38x has been added. Done by Grégory Clement.
    • cpuidle support for Armada XP has been added. Done by Grégory Clement.
    • USB support (USB2 and USB3) for Armada 375 and Armada 38x has been added. Done by Grégory Clement.
    • Hardware I/O coherency support for Armada 375 and Armada 38x. Done by Thomas Petazzoni.
    • Enabling of the SDHCI and AHCI interfaces on Armada 38x. Done by Thomas Petazzoni.
    • Major clean-up of Marvell Orion5x support. This is an older ARMv5 family of processors from Marvell, having a lot of similarities with Kirkwood and more recent Armada. This cleanup include many Device Tree conversions, up to the point where a few Marvell Orion5x platforms can now be fully described using a Device Tree, with no board file. Done by Thomas Petazzoni.
    • Addition of a new Device Tree binding for fixed network links, i.e links that do not use a MDIO-controlled PHY. This involved both some generic PHY layer improvements, and corresponding changes in the Marvell-specific mvneta network driver. Done by Thomas Petazzoni.
    • Addition of a work-around for a relatively complex PCIe/L2 errata affecting Armada 375/38x, which fixes heavy PCIe traffic when the system is running with hardware I/O coherency enabled. Done by Thomas Petazzoni.

Here is the complete list of patches from Bootlin merged into the 3.16 kernel:

Linux 3.15 released, an overview of Bootlin contributions

The 3.15 of the Linux kernel was released just a few days ago by Linus Torvalds. As explained by LWN.net, the headline features in 3.15 include some significant memory management improvements, the renameat2() system call, file-private POSIX locks, a new device mapper target called dm-era, faster resume from suspend, and more. One can also read the coverage by LWN.net of the first part and the second part of the merge window to get more details about the major new features in this release.

As usual, Bootlin contributed to the Linux kernel during this 3.15 cycle, and with a total of 218 patches contributed, it’s a new record for Bootlin. According to the KPS statistics, Bootlin ranked #12 in the list of companies contributing to the Linux kernel for the 3.15 kernel (if you exclude the “Unknown” and “Hobbyists” categories, which aren’t really companies).

The main features contributed by Bootlin again centered around the support for ARM processors:

  • By far, the largest contribution this cycle was the initial support for the new Armada 375 and Armada 38x processors from Marvell. Gregory Clement, Ezequiel Garcia and Thomas Petazzoni have been working on the code to support these processors since a few months ago, and started pushing the patches to the public in February this year. For the Marvell Armada 38x processor, it means that the code was pushed in mainline even before the processor was announced publicly! The features supported in 3.15 for these processors are: interrupts, GPIO, clocks, pin-muxing, serial, I2C, SPI, timer, L2 cache, SDIO (only for 375), SATA (only 375), XOR, PCIe, MBus, networking (only for 38x), NOR and NAND support. Many other features such as SMP, I/O coherency and various other peripherals will be supported in 3.16.
  • Convert support for the Atmel AT91SAM9RL processor to the Device Tree, done by Alexandre Belloni.
  • Addition of iio-hwmon to the Freescale i.MX23 and i.MX28 processors, which allows to use the internal temperature sensor of the processor. Done by Alexandre Belloni.
  • Multiple fixes and improvements to the AT91 ADC support. Done by Alexandre Belloni.
  • Support for the watchdog in Armada 370 and Armada XP was added, done by Ezequiel Garcia.
  • A driver for the SPI controller found in Allwinner A31 SoC was added, as well as all the Device Tree information to describe this controller and related clocks. Done by Maxime Ripard.
  • Support for the I2C controller found in the Allwinner A31 SoC was added into the existing mv64xxx-i2c driver, as well as the necessary Device Tree information to use I2C on this SoC. Done by Maxime Ripard.
  • Audio support was enabled on the Armada 370 SoC, re-using existing code for Kirkwood, and therefore making audio work on the Armada 370 DB platform. Done by Thomas Petazzoni.
  • A number of issues in the PCIe support for Marvell processors have been fixed, thanks to the reports from a number of users. Done by Thomas Petazzoni, with help from these users.

We also contributed other things than just support for ARM processors:

  • The main contribution in this area is the addition of UBI block, a driver that allows to use read-only block filesystems such as squashfs on top of a UBI volume. The code was originally written by David Wagner who was an intern at Bootlin, and later taken by Ezequiel Garcia who did a lot of additional cleanup work and community discussion to get the driver merged. Some details about this feature can be found in the Linux-MTD documentation.
  • A generic Device Tree binding to express NAND ECC related information in the Device Tree was contributed by Ezequiel Garcia.
  • The quest to remove IRQF_DISABLED continued, by Michael Opdenacker.

In details, all our contributions are:

Marvell publishes the datasheet of the Armada 370 processor

thumb-armada-xpOver the last two years, Bootlin has contributed support for the Marvell Armada 370 and Marvell Armada XP processors to the mainline Linux kernel. These ARM processors are used mainly in Network Attached Storage devices but also in other devices such as printers. Until now the datasheet for these processors was only available for Marvell customers and partners under NDA, but last week, Marvell finally released the datasheet of the Armada 370 publicly, with no restriction, no registration, no NDA. The Armada 370 processor can already be found in several consumer grade products:

From now on, on the Marvell page (broken link removed) related to the Armada 3xx family, the Armada 370 Functional Specification (broken link removed) as well as the Armada 370 Hardware Specifications (broken link removed) can be found. While the Armada XP datasheet is not available at this time, it is worth mentioning that the vast majority of the peripherals are exactly the same between Armada 370 and Armada XP, so even Armada XP users will find useful information in this datasheet.

Bootlin is happy to see that Marvell is making more and more progress towards mainlining their kernel support and opening their datasheets publicly. We strongly believe that the openness of these datasheets will allow hobbyists and developers to improve the support for Armada 370 in the open-source ecosystem, be it in the Linux kernel, in bootloaders like U-Boot or Barebox or even in other projects.

2014 Q2 newsletter

Bootlin is happy to share some news about the latest training and contribution activities of the company.

Linux 3.14 released, Bootlin contributions inside!

Linus Torvalds has just released the 3.14 version of the Linux kernel. As usual, it incorporates a large number of changes, for which a good summary is available on the KernelNewbies site.

This time around, Bootlin is the 19th company contributing to this kernel release, by number of patches, right between Cisco and Renesas. Six of our engineers have contributed to this release: Maxime Ripard, Alexandre Belloni, Ezequiel Garcia, Grégory Clement, Michael Opdenacker and Thomas Petazzoni. In total, they have contributed 121 patches to this kernel release.

  • By far, the largest number of patches are related to the addition of NAND support for the Armada 370 and Armada XP processors. This required a significant effort, done by Ezequiel Garcia, to re-use the existing pxa3xx_nand driver and extend it to cover the specificities of the Armada 370/XP NAND controller. And these specificities were quite complicated, involving a large number of changes to the driver, which all had to also be validated on existing PXA3xx hardware to not introduce any regression.
  • Support for high speed timers on various Allwinner SOCs has been added by Maxime Ripard.
  • Support for the Allwinner reset controller has been implemented by Maxime Ripard.
  • SMP support for the Allwinner A31 SOC was added by Maxime Ripard.
  • A number of small fixes and improvements were made to the AT91 pinctrl driver and the pinctrl subsystem by Alexandre Belloni.
  • Michael Opdenacker continued his quest to finally get rid of the IRQF_DISABLED flag.
  • A number of fixes and improvements were made by Grégory Clement and Thomas Petazzoni on various Armada 370/XP drivers: fix for the I2C controller on certain early Armada XP revisions, fixes to make the Armada 370/XP network driver usable as a module, etc.

In detail, our contributions were:

Bootlin contributions to Linux 3.13

Version 3.13 of the Linux kernel was released by Linus Torvalds on January, 19th 2014. The kernelnewbies.org site has an excellent page that covers the most important improvements and feature additions that this new kernel release brings.

As usual Bootlin contributed to this kernel: with 121 patches merged in 3.13 on a total of 12127 patches contributed, Bootlin is ranked 17th in the list of companies contributing to the Linux kernel. We also appeared on Jonathan Corbet kernel contribution statistics at LWN.net, as a company having contributed 1% of the kernel changes, right between Renesas Electronics and Huawei Technologies.

Amongst the contributions we made for 3.13:

  • Standby support added to the Marvell Kirkwood processors, done by Ezequiel Garcia.
  • Various fixes and improvements to the PXA3xx NAND driver, as well as to the Marvell Armada 370/XP clocks, in preparation to the introduction of NAND support for Armada 370/XP, which will arrive in 3.14. Work done by Ezequiel Garcia.
  • Added support for the Performance Monitoring Unit in the AM33xx Device Tree files, which allows to use perf and oprofile on platforms such as the BeagleBone. Work done by Alexandre Belloni.
  • Support added for the I2C controllers on certain Allwinner SOCs, as well as several other cleanups and minor improvements for these SoCs. Work done by Maxime Ripard.
  • Continued the work to get rid of IRQF_DISABLED, as well as other janitorial tasks such as removing unused Kconfig symbols. Work done by Michael Opdenacker.
  • Added support for MSI (Message Signaled Interrupts) for the Armada 370 and XP SoCs. Work done by Thomas Petazzoni.
  • Added support for the Marvell Matrix board (an Armada XP based platform) and the OpenBlocks A7 (a Kirkwood based platform manufactured by PlatHome). Work done by Thomas Petazzoni.

In detail, the patches contributed by Bootlin are:

Bootlin New Year – 2014

A French version also exists.

The Bootlin team wishes you a Happy New Year for 2014, with plenty of optimism and energy!

We are taking this opportunity to give some news about Bootlin.

In 2013, Bootlin significantly increased its contribution to open-source projects, especially at the Linux kernel level.

639 patches integrated in the Linux kernel, mainly to improve support for Marvell ARM processors and Allwinner ARM processors. For all kernel releases published in 2013, Bootlin has been in the top 30 contributing companies. We now have a significant experience in integrating support for ARM processors in the Linux kernel, and we expect to work more in this area in 2014.

595 patches integrated in the Buildroot embedded Linux build system, in a large number of areas, making Bootlin the second most important contributor after Buildroot’s maintainer. This effort allows Bootlin to keep an up-to-date expertise in cross-compilation and build systems.

26 patches integrated in the Barebox bootloader:

22 patches to the Yocto Freescale layer, mainly adding support for the Crystalfontz boards. In the process, a new image type was developed and significant improvements were made to the Barebox recipe.

Several of these contributions, and many other activities, were driven by development and consulting activities in 2013, with mainly:

  • Linux kernel code development, adding and maintaining support for customer ARM processors or boards in the mainline Linux kernel. Especially on Marvell and Freescale processors.
  • Linux kernel, driver development and build system integration for an Atmel SAMA5 based medical device.
  • Development of Linux kernel drivers for radio-frequency transceivers, on an Atmel SAMA5 based home automation platform.
  • Boot time optimization audits.
  • Buildroot consulting and audit.

We have also significantly improved and updated our training courses:

  • Our embedded Linux and kernel driver development course was updated to use the BeagleBone Black platform, to cover the usage of the Device Tree on ARM platform, and to use a fun I2C device to illustrate the development of a device driver in our labs.
  • Our Android system development course was updated to use Android 4.x, and use the BeagleBone Black as the development platform for the practical labs.
  • Our embedded Linux system development course was updated to use more recent versions of the Linux kernel, in order to cover the usage of the Device Tree on ARM platforms.

Our training materials remain freely available under a Creative Commons license, including their source code, available from a public Git repository.

Bootlin continues to believe that participating to conferences is critical to keep its engineers up to date with the latest Linux developments and create connections with the developers of the Linux community which are essential to make our projects progress faster. For this purpose, we participated to a large number of conferences in 2013:

  • FOSDEM 2013, in Brussels, Belgium. Our CTO and engineer Thomas Petazzoni gave a talk about ARM kernel development
  • Buildroot Developers Meeting, Brussels, Belgium. Our engineer Thomas Petazzoni organized and participated to this 2-days meeting, sponsored by Google, to work on Buildroot developments.
  • Embedded Linux Conference 2013 and Android Builders Summit 2013, in San Francisco, United States. Our engineer Gregory Clement gave a talk about the Linux kernel clock framework. Our engineer Thomas Petazzoni gave a talk about ARM kernel development. See also our videos.
  • Linaro Connect Europe 2013, Dublin Ireland. Our engineer Thomas Petazzoni participated to numerous discussions related to support for ARM processors in the Linux kernel.
  • Linux Plumbers 2013, New Orleans, United States. Our engineer Maxime Ripard attended the conference, and participated to discussions around Android and Linux kernel development.
  • Kernel Recipes, Paris, France. Both Bootlin CEO Michael Opdenacker and CTO Thomas Petazzoni participated to this Linux kernel conference, and Thomas gave two talks: one about ARM kernel development and one about Buildroot.
  • ARM kernel mini-summit 2013, Edinburgh, UK. Our engineers Gregory Clement, Thomas Petazzoni and Maxime Ripard participated to the invitation-only ARM kernel mini-summit. This summit is the key place to discuss and define the next directions for support for ARM processors in the Linux kernel.
  • Embedded Linux Conference Europe, Edinburgh, UK. Gregory Clement gave a talk about about the Linux kernel clock framework and Thomas Petazzoni gave a talk about the Device Tree.
  • Buildroot Developers Meeting, Edinburgh, UK. Our engineer Thomas Petazzoni organized and participated to this 2-days meeting, sponsored by Imagination Technologies, to work on Buildroot development.

A very important development of Bootlin in 2013 is the addition of a new engineer to our team: Alexandre Belloni joined us in March 2013. Alexandre has a very significant embedded Linux and kernel experience, see his profile.

Now, let’s talk about our plans for 2014:

  • Hire several additional engineers. One of them has already been hired and will join us in April, bringing a significant Linux kernel development experience, including mainline contribution.
  • Our involvement in support for ARM processors in the Linux kernel will grow significantly.
  • Two new training courses will be released: one “Boot time reduction” training course, and an “OpenEmbedded and Yocto” training course.
  • For the first time, we will organize public training sessions (open to individual registration) outside of France.
    • Our next Android system development session in English will happen on April 14-17 in Southampton, UK
    • We are also working on embedded Linux and Kernel and driver development sessions in the USA, to be announced in the next weeks.
    • We also plan to organize embedded Linux and Kernel and driver development sessions in Germany, with German speaking trainers.
    • By the way, our Android system development courses in French will continue to run in Toulouse, but there will also be a session on April 1-4 in Lyon.

    See also the full list of public sessions.

As in 2013, we will participate to several key conferences. We have already planned our participation to: Linux Conf Australia (January 2014), FOSDEM (February 2014), Embedded Linux Conference (April 2014) and the Embedded Linux Conference Europe (October 2014).

You can follow Bootlin news by reading our blog and by following our quick news on Twitter. We now have a Google+ page too.

Again, Happy New Year!

The Bootlin team.

New training materials: boot time reduction workshop

We are happy to release new training materials that we have developed in 2013 with funding from Atmel Corporation.

The materials correspond to a 1-day embedded Linux boot time reduction workshop. In addition to boot time reduction theory, consolidating some of our experience from our embedded Linux boot time reduction projects, the workshop allows participants to practice with the most common techniques. This is done on SAMA5D3x Evaluation Kits from Atmel.

The system to optimize is a video demo from Atmel. We reduce the time to start a GStreamer based video player. During the practical labs, you will practice with techniques to:

  • Measure the various steps of the boot process
  • Analyze time spent starting system services, using bootchartd
  • Simplify your init scripts
  • Trace application startup with strace
  • Find kernel functions taking the most time during the boot process
  • Reduce kernel size and boot time
  • Replace U-Boot by the Barebox bootloader, and save a lot of time
    thanks to the activation of the data cache.

Creative commonsAs usual, our training materials are available under the terms of the Creative Commons Attribution-ShareAlike 3.0 license. This essentially means that you are free to download, distribute and even modify them, provided you mention us as the original authors and that you share these documents under the same conditions.

Special thanks to Atmel for allowing us to share these new materials under this license!

Here are the documents at last:

The first public session of this workshop will be announced in the next weeks.
Don’t hesitate to contact us if you are interested in organizing a session on your site.

Linux init failures now easier to debug

If you are an embedded Linux developer too, you have probably been frustrated by the lack of information from the Linux kernel when it failed to start the init process when you’re building a new root filesystem. The only thing you get is No init found, and this could hide many different causes:

  • No init program candidate found at all
  • Some init program candidates exist but they can’t be executed, for multiple possible causes (missing execute permissions, failed to load shared libraries, executable compiled for an unknown architecture…)

The good news is that this source of frustration will be gone in Linux 3.13. Thanks to a Bootlin commit merged on Nov. 13, 2013, whenever an attempt to execute an init program candidate fails, there is a message in the console detailing the executable path and the error code. For example:

Starting init: /sbin/init exists but couldn't execute it (error -13)

When you get such a message, all you have to do is lookup the error code in include/uapi/asm-generic/errno-base.h or maybe in uapi/asm-generic/errno.h. In the above example, the -13 code meant permission denied, typically because of missing execution rights.

This had been annoying me for a long time, and I am glad that the Linux kernel community accepted my improvement!

By the way, many more improvements to the Linux kernel from Bootlin are currently getting merged in 3.13. See all our contributions to the Linux kernel.