Author: Thomas Petazzoni

Thomas Petazzoni is Bootlin's co-owner and CEO. Thomas joined Bootlin in 2008 as a kernel and embedded Linux engineer, became CTO in 2013, and co-owner/CEO in 2021. More details...

Linux 4.9 released, Bootlin contributions

Linus Torvalds has released the 4.9 Linux kernel yesterday, as was expected. With 16214 non-merge commits, this is by far the busiest kernel development cycle ever, but in large part due to the merging of thousands of commits to add support for Greybus. LWN has very well summarized what’s new in this kernel release: 4.9 Merge window part 1, 4.9 Merge window part 2, The end of the 4.9 merge window.

As usual, we take this opportunity to look at the contributions Bootlin made to this kernel release. In total, we contributed 116 non-merge commits. Our most significant contributions this time have been:

  • Bootlin engineer Boris Brezillon, already a maintainer of the Linux kernel NAND subsystem, becomes a co-maintainer of the overall MTD subsystem.
  • Contribution of an input ADC resistor ladder driver, written by Alexandre Belloni. As explained in the commit log: common way of multiplexing buttons on a single input in cheap devices is to use a resistor ladder on an ADC. This driver supports that configuration by polling an ADC channel provided by IIO.
  • On Atmel platforms, improvements to clock handling, bug fix in the Atmel HLCDC display controller driver.
  • On Marvell EBU platforms
    • Addition of clock drivers for the Marvell Armada 3700 (Cortex-A53 based), by Grégory Clement
    • Several bug fixes and improvements to the Marvell CESA driver, for the crypto engine founds in most Marvell EBU processors. By Romain Perier and Thomas Petazzoni
    • Support for the PIC interrupt controller, used on the Marvell Armada 7K/8K SoCs, currently used for the PMU (Performance Monitoring Unit). By Thomas Petazzoni.
    • Enabling of Armada 8K devices, with support for the slave CP110 and the first Armada 8040 development board. By Thomas Petazzoni.
  • On Allwinner platforms
    • Addition of GPIO support to the AXP209 driver, which is used to control the PMIC used on most Allwinner designs. Done by Maxime Ripard.
    • Initial support for the Nextthing GR8 SoC. By Mylène Josserand and Maxime Ripard (pinctrl driver and Device Tree)
    • The improved sunxi-ng clock code, introduced in Linux 4.8, is now used for Allwinner A23 and A33. Done by Maxime Ripard.
    • Add support for the Allwinner A33 display controller, by re-using and extending the existing sun4i DRM/KMS driver. Done by Maxime Ripard.
    • Addition of bridge support in the sun4i DRM/KMS driver, as well as the code for a RGB to VGA bridge, used by the C.H.I.P VGA expansion board. By Maxime Ripard.
  • Numerous cleanups and improvements commits in the UBI subsystem, in preparation for merging the support for Multi-Level Cells NAND, from Boris Brezillon.
  • Improvements in the MTD subsystem, by Boris Brezillon:
    • Addition of mtd_pairing_scheme, a mechanism which allows to express the pairing of NAND pages in Multi-Level Cells NANDs.
    • Improvements in the selection of NAND timings.

In addition, a number of Bootlin engineers are also maintainers in the Linux kernel, so they review and merge patches from other developers, and send pull requests to other maintainers to get those patches integrated. This lead to the following activity:

  • Maxime Ripard, as the Allwinner co-maintainer, merged 78 patches from other developers.
  • Grégory Clement, as the Marvell EBU co-maintainer, merged 43 patches from other developers.
  • Alexandre Belloni, as the RTC maintainer and Atmel co-maintainer, merged 26 patches from other developers.
  • Boris Brezillon, as the MTD NAND maintainer, merged 24 patches from other developers.

The complete list of our contributions to this kernel release:

Buildroot 2016.11 released, Bootlin contributions

Buildroot LogoThe 2016.11 release of Buildroot has been published on November, 30th. The release announcement, by Buildroot maintainer Peter Korsgaard, gives numerous details about the new features and updates brought by this release. This new release provides support for using multiple BR2_EXTERNAL directories, gives some important updates to the toolchain support, adds default configurations for 9 new hardware platforms, and 38 new packages were added.

On a total of 1423 commits made for this release, Bootlin contributed a total of 253 commits:

$ git shortlog -sn --author=free-electrons 2016.08..2016.11
   142  Gustavo Zacarias
   104  Thomas Petazzoni
     7  Romain Perier

Here are the most important contributions we did:

  • Romain Perier contributed a package for the AMD Catalyst proprietary driver. Such drivers are usually not trivial to integrate, so having a ready-to-use package in Buildroot will really make it easier for Buildroot users who use hardware with an AMD/ATI graphics controller. This package provides both the X.org driver and the OpenGL implementation. This work was sponsored by one of Bootlin customer.
  • Gustavo Zacarias mainly contributed a large set of patches that do a small update to numerous packages, to make sure the proper environment variables are passed. This is a preparation change to bring top-level parallel build in Buildroot. This work was also sponsored by another Bootlin customer.
  • Thomas Petazzoni did contributions in various areas:
    • Added a DEVELOPERS file to the tree, to reference which developers are interested by which architectures and packages. Not only it allows the developers to be Cc’ed when patches are sent on the mailing list (like the get_maintainers script does), but it also used by Buildroot autobuilder infrastructure: if a package fails to build, the corresponding developer is notified by e-mail.
    • Misc updates to the toolchain support: switch to gcc 5.x by default, addition of gcc patches needed to fix various issues, etc.
    • Numerous fixes for build issues detected by Buildroot autobuilders

In addition to contributing 104 commits, Thomas Petazzoni also merged 1095 patches from other developers during this cycle, in order to help Buildroot maintainer Peter Korsgaard.

Finally, Bootlin also sponsored the Buildroot project, by funding the meeting location for the previous Buildroot Developers meeting, which took place in October in Berlin, after the Embedded Linux Conference. See the Buildroot sponsors page, and also the report from this meeting. The next Buildroot meeting will take place after the FOSDEM conference in Brussels.

Bootlin at Linux.conf.au, January 2017

Linux.conf.au, which takes place every year in January in Australia or New Zealand, is a major event of the Linux community. Bootlin already participated to this event three years ago, and will participate again to this year’s edition, which will take place from January 16 to January 20 2017 in Hobart, Tasmania.

Linux Conf Australia 2017

This time, Bootlin CTO Thomas Petazzoni will give a talk titled A tour of the ARM architecture and its Linux support, in which he will share with LCA attendees what is the ARM architecture, how its Linux support is working, what the numerous variants of ARM processors and boards mean, what is the Device Tree, the ARM specific bootloaders, and more.

Linux.conf.au also features a number of other kernel related talks, such as the Kernel Report from Jonathan Corbet, Linux Kernel memory ordering: help arrives at last from Paul E. McKenney. The list of conferences is very impressive, and the event also features a number of miniconfs, including one on the Linux kernel.

If some of our readers located in Australia, New Zealand or neighboring countries plan on attending the conference, do not hesitate to drop us a mail so that we can meet during the event!

Slides and videos from the Embedded Linux Conference Europe 2016

Last month, the entire Bootlin engineering team attended the Embedded Linux Conference Europe in Berlin. The slides and videos of the talks have been posted, including the ones from the seven talks given by Bootlin engineers:

  • Alexandre Belloni presented on ASoC: Supporting Audio on an Embedded Board, slides and video.
  • Boris Brezillon presented on Modernizing the NAND framework, the big picture, slides and video.
  • Boris Brezillon, together with Richard Weinberger from sigma star, presented on Running UBI/UBIFS on MLC NAND, slides and video.
  • Grégory Clement presented on Your newer ARM64 SoC Linux check list, slides and video.
  • Thomas Petazzoni presented on Anatomy of cross-compilation toolchains, slides and video.
  • Maxime Ripard presented on Supporting the camera interface on the C.H.I.P, slides and video.
  • Quentin Schulz and Antoine Ténart presented on Building a board farm: continuous integration and remote control, slides and video.

Bootlin at the Kernel Recipes conference

Kernel RecipesThe 2016 edition of the Kernel Recipes conference will take place from September 28th to 30th in Paris. With talks from kernel developers Jonathan Corbet, Greg Kroah-Hartmann, Daniel Vetter, Laurent Pinchart, Tejun Heo, Steven Rosdedt, Kevin Hilman, Hans Verkuil and many others, the schedule looks definitely very appealing, and indeed the event is now full.

Thomas Petazzoni, Bootlin CTO, will be attending this event. If you’re interested in discussing business or career opportunities with Bootlin, this event will be a great place to meet together.

Bootlin at the X Developer Conference

The next X.org Developer Conference will take place on September 21 to September 23 in Helsinki, Finland. This is a major event for Linux developers working in the graphics/display areas, not only at the X.org level, but also at the kernel level, in Mesa, and other related projects.

Bootlin engineer Maxime Ripard will be attending this conference, with 80+ other engineers from Intel, Google, NVidia, Texas Instruments, AMD, RedHat, etc.

Maxime is the author of the DRM/KMS driver in the upstream Linux kernel for the Allwinner SoCs, which provides display support for numerous Allwinner platforms, especially Nextthing’s CHIP (with parallel LCD support, HDMI support, VGA support and composite video support). Maxime has also worked on making the 3D acceleration work on this platform with a mainline kernel, by adapting the Mali kernel driver. Most recently, Maxime has been involved in Video4Linux development, writing a driver for the camera interface of Allwinner SoCs, and supervising Florent Revest work on the Allwinner VPU that we published a few days ago.

Bootlin mentioned in Linux Foundation’s report

Linux Kernel Development Report 2016Lask week, the Linux Foundation announced the publication of the 2016 edition of its usual report “Linux Kernel Development – How Fast It is Going, Who is Doing It, What They are Doing, and Who is Sponsoring It”.

This report gives a nice overview of the evolution of the Linux kernel since 3.18, especially from a contribution point of view: the rate of changes, who is contributing, are there new developers joining, etc.

Bootlin is mentioned in several places in this report. First of all, even though Bootlin is a consulting company, it is shown individually rather than part of the general “consultants” category. As the report explains:

The category “consultants” represents developers who contribute to the kernel as a work-for-hire effort from different companies. Some consultant companies, such as Bootlin and Pengutronix, are shown individually as their contributions are a significant number.

Thanks to being mentioned separately from the “consultants” category, the report also shows that:

  • Bootlin is the #15 contributing company over the 3.19 to 4.7 development period, in number of commits. Bootlin contributed a total of 1453 commits, corresponding to 1.3% of the total commits
  • Bootlin is ranked #13 in the list of companies by number of Signed-off-by from developers who are not the author of patches. This happens because 6 of our engineers are maintainers or co-maintainers from various areas in the kernel: they merge patches from contributors, sign-off on them, and send them to another maintainer (either arm-soc maintainers or directly Linus Torvalds, depending on the subsystem).

We’re glad to see Bootlin mentioned in this report, which shows that we are a strong contributor to the official Linux kernel. Thanks to this contribution effort, we have tremendous experience with adding support for new hardware in the kernel, so contact us if you want your hardware supported in the official Linux kernel!

Support for the Allwinner VPU in the mainline Linux kernel

Over the last few years, and most recently with the support for the C.H.I.P platform, Bootlin has been heavily involved in initiating and improving the support in the mainline Linux kernel for the Allwinner ARM processors. As of today, a large number of hardware features of the Allwinner processors, especially the older ones such as the A10 or the A13 used in the CHIP, are usable with the mainline Linux kernel, including complex functionality such as display support and 3D acceleration. However, one feature that was still lacking is proper support for the Video Processing Unit (VPU) that allows to accelerate in hardware the decoding and encoding of popular video formats.

During the past two months, Florent Revest, a 19 year old intern at Bootlin worked on a mainline solution for this Video Processing Unit. His work followed the reverse engineering effort of the Cedrus project, and this topic was also listed as a High Priority Reverse Engineering Project by the FSF.

The internship resulted in a new sunxi-cedrus driver, a Video4Linux memory-to-memory decoder kernel driver and a corresponding VA-API backend, which allows numerous userspace applications to use the decoding capabilities. Both projects have both been published on Github:

Currently, the combination of the kernel driver and VA-API backend supports MPEG2 and MPEG4 decoding only. There is for the moment no support for encoding, and no support for H264, though we believe support for both aspects can be added within the architecture of the existing driver and VA-API backend.

A first RFC patchset of the kernel driver has been sent to the linux-media mailing list, and a complete documentation providing installation information and architecture details has been written on the linux-sunxi’s wiki.

Here is a video of VLC playing a MPEG2 demo video on top of this stack on the Next Thing’s C.H.I.P:

Bootlin at the Embedded Linux Conference Europe

The next Embedded Linux Conference Europe will take place from October 11 to October 13 in Berlin, Germany. As usual, the entire Bootlin engineering team will participate, which means this time 10 participants from Bootlin!

Embedded Linux Conference Europe 2016

The schedule for the conference has been published recently, and a number of our talk proposals have been accepted, so we will present on the following topics:

Like every year, we’re looking forward to attending this conference, and meeting all the nice folks of the Embedded Linux community!

Linux 4.7 statistics: Bootlin engineer #2 contributor

LWN.net has published yesterday an article containing statistics for the 4.7 development cycle. This article is available for LWN.net subscribers only during the coming week, and will then be available for everyone, free of charge.

It turns out that Boris Brezillon, Bootlin engineer, is the second most active contributor to the 4.7 kernel in number of commits! The top three contributors in number of commits are: H Hartley Sweeten (208 commits), Boris Brezillon (132 commits) and Al Viro (127 commits).

LWN.net 4.7 kernel statistics

In addition to being present in the most active developers by number of commits, Boris Brezillon is also in the #11 most active contributor in terms of changed lines. As we discussed in our previous blog post, most contributions from Boris were targeted at the PWM subsystem on one side (atomic update support) and the NAND subsystem on the other side.

Another Bootlin engineer shows up in the per-developer statistics: Maxime Ripard is the #17 most active contributor by lines changed. Indeed, Maxime contributed a brand new DRM/KMS driver for the Allwinner display controller.

As a company, Bootlin is ranked for the 4.7 kernel as the #12 most active company by number of commits, and #10 by number of changed lines. We are glad to continue being such a contributor to the Linux kernel development, as we have been for the last four years. If you want your hardware to be supported in the official Linux kernel, contact us!