Linux 5.5 released, Bootlin contributions inside

Linux 5.5 was recently released, as usual bringing a large number of new features and improvements, which are nicely detailed in the LWN articles on merge window part 1 and merge window part 2, but also on the Kernelnewbies wiki.

According to the statistics, a total of 14350 changes were made to this kernel release, to which Bootlin contributed 124 patches, making us the 19th contributing company by number of commits. Here are the highlights of our contributions:

  • By far and large our most important achievement in Linux 5.5 is the merge of the H265 decoding support in the Allwinner VPU driver, developed by Paul Kocialkowski. This was the last missing feature to complete the effort funded by the Kickstarter campaign we launched in February 2018. See our blog post wrapping up the Allwinner VPU work.
  • Alexandre Belloni as the RTC subsystem maintainer, as usual contributed a large number of RTC driver improvements and fixes.
  • Antoine Ténart contributed some improvements to the Cadence MACB driver, most notably used as the Ethernet controller driver on Microchip/Atmel platforms. The main improvement is the conversion to the phylink subsystem for the interaction with the Ethernet PHY.
  • Grégory Clement contributed numerous enhancements to the Microchip/Atmel SPI controller driver, mainly aimed at fixing and improving the support for Chip Select, both native Chip Selects and GPIO-based Chip Selects.
  • Kamel Bouhara contributed a few additional Device Tree files to describe home automation hardware platforms from Overkiz, based on the Microchip SAMA5D2 processor, as well as an improvement to a Microchip SoC driver that allows to expose the platform serial number to user-space.
  • Miquèl Raynal added support for a new Marvell system-on-chip called Marvell CN9130. Despite the name, this chip is from a hardware point of view in the same family as the Marvell Armada 7K and 8K, which were already supported upstream.
  • Miquèl Raynal contributed a number of fixes and improvements to the Macronix SPI controller driver.
  • Miquèl Raynal added support for the ADC converters over SPI MAX1227, MAX1229 and MAX1231 to the existing max1027 IIO driver in the kernel. These ADCs have a 12-bit resolution.
  • Miquèl Raynal improved the SPI controller driver for the Zynq system-on-chips to correctly support multiple Chip Selects.

In addition to these direct contributions, some of the Bootlin engineers are also Linux kernel maintainers and therefore review and merge patches from other contributors: Alexandre Belloni as the RTC subsystem maintainer and Microchip platform co-maintainer reviewed and merged 45 patches from other contributors, Miquèl Raynal as the MTD subsystem co-maintainer reviewed and merged 39 patches from other contributors and Grégory Clement as the Marvell platform co-maintainer reviewed and merged 29 patches from other contributors.

Here is the detail of our contributions:

Bootlin at FOSDEM and Buildroot Developers Meeting

FOSDEM 2020This week-end takes place one of the biggest and most important free and open-source software conference in Europe: FOSDEM. It will once again feature a very large number of talks, organized in several main tracks and developer rooms.

Bootlin CTO Thomas Petazzoni will participate to the FOSDEM conference, of course attending many of the talks from the Embedded, Mobile and Automative Devroom, to which he participated to the talk review and selection. Do not hesitate to get in touch with Thomas if you want to discuss career or business opportunities with Bootlin.

In addition, Thomas will also participate to the 3-day Buildroot Developers meeting which takes place in Brussels right after the FOSDEM conference, kindly hosted by Google. During 3 days, some of the core Buildroot developers will work together to discuss the future of Buildroot, as well as review and discuss pending patches and proposals.

Building a Linux system for the STM32MP1: implementing factory flashing

After several months, it’s time to resume our series of blog posts about building a Linux system for the STM32MP1 platform. After showing how to build a minimal Linux system for the STM32MP157 platform, how to connect and use an I2C based pressure/temperature/humidity sensor and how to integrate Qt5 in our system, how to set up a development environment to write our own Qt5 application and how to develop a Qt5 application, we will now cover the topic of factory flashing.

List of articles in this series:

  1. Building a Linux system for the STM32MP1: basic system
  2. Building a Linux system for the STM32MP1: connecting an I2C sensor
  3. Building a Linux system for the STM32MP1: enabling Qt5 for graphical applications
  4. Building a Linux system for the STM32MP1: setting up a Qt5 application development environment
  5. Building a Linux system for the STM32MP1: developing a Qt5 graphical application
  6. Building a Linux system for the STM32MP1: implementing factory flashing
  7. Building a Linux system for the STM32MP1: remote firmware updates

What is factory flashing ?

So far, we have used a microSD card as storage for the Linux system running on the STM32MP1 platform. Since this media is removable, we can easily switch the microSD card back and forth between the STM32MP1 platform and our development workstation, which is nice during development and debugging.

However, an actual product will most likely use some form of non-removable persistent storage, typically an eMMC or a NAND flash. While not available on the STM32MP1-DK1 board probably for cost reasons, these storage devices are very common in most embedded systems. For example, the STM32MP157A-EV1 board provides three non-removable persistent storage devices: a 4 GB eMMC, a 1 GB NAND flash, and a 64 MB QSPI NOR flash.

When such storage devices are shipped by their manufacturer, they are typically empty. Therefore, as part of the manufacturing process of your embedded systems, you will have to load the relevant storage device with your Linux system, applications and data, so that the embedded system is fully operational: this is the process referred to as factory flashing in this blog post.

If you are doing a very high volume product, you can ask your eMMC or NAND flash vendor to pre-load a system image on the storage before it is shipped to you and assembled on your board. However, many companies do products with volumes that are not large enough to make such a strategy possible: in this case, you really receive an empty storage device, and have to flash it.

A first possibility to flash the non-removable storage is to use a removable storage device, boot a Linux system on the device, and use it to flash the non-removable storage. This can definitely be a possible option in some situations, but it is not always possible (if there’s no removable storage device interface at all) or not always practical.

However, most system-on-chips, including the STM32MP1 include some ROM code that the processor executes at boot time, even before it loads the first stage bootloader. This ROM code is primarly responsible for loading the first stage bootloader into memory, but it also very often offers a communication channel with the outside world, which can be used to gain control of a platform that has nothing at all on its storage. This communication channel is typically over USB or UART, and most often uses a custom, vendor-specific protocol, which is understood by vendor-specific tools. This protocol generally allows to send some code to the target and get it executed, which is sufficient to be able to reflash the target device.

Here are a few examples with system-on-chips from various vendors:

  • The ROM code of the NXP i.MX processors implements a USB-based protocol, which can be interfaced either using the NXP-provided mfgtools, or using the community-developed imx_usb_loader. The latter was presented in one of our earlier blog posts about i.MX6 factory flashing.
  • The ROM code of Microchip SAMA5 processors implements a USB-based protocol, which can be interfaced using a tool called SAM-BA
  • The ROM code of Rockchip processors implements a USB-based protocol, which can be interfaced either using a Rockchip-specific tool called rkdeveloptool
  • The ROM code of the ST STM32MP15 processors also implement a USB-based protocol, which can be interfaced using the STM32 Cube Programmer

Obviously, in this blog post, we are going to use the latter, STM32 Cube Programmer, to flash our STM32MP1 platform. Since the DK2 board only has a removable device, we will use the tool to flash the SD card, but the process and logic would be the same for any other (non-removable) storage device.

Getting and installing STM32 Cube Programmer

While ST generally has very good upstream and open-source support for its products, the STM32 Cube Programmer unfortunately doesn’t follow this strategy: you need to be registered on the ST web site to download it, and its source code is not available. Due to this registration process, we for example cannot create a Buildroot package that would automatically download and install this tool for you.

So, follow the process to create an account on the ST web site, and then go to the STM32 Cube Programmer page. At the time of this writing, the latest version is 2.2.1, but according this Wiki page, this version doesn’t work for the STM32MP1 platform. Instead, select to download the 2.2.0 version, which is known to work. You will then download a file called (it doesn’t have the version in its name, which isn’t great) weighting 187 MB, and which has the SHA256 hash 91107b4d605d126f5c32977247d7419d42abb2655848d2d1a16d52f5f7633d2d.

Extract this ZIP file somewhere in your system, and then run the SetupSTM32CubeProgrammer-2.2.0.linux executable:

$ ./SetupSTM32CubeProgrammer-2.2.0.linux

Got through the installation steps. On our system, we customized the installation path to be just $HOME/stm32cube, and the remainder of this blog post will assume this is where you installed the STM32 Cube Programmer.

In this blog post, we are only going to use the command line interface (CLI) of STM32 Cube Programmer, so just make sure you can run the corresponding tool:

$ ~/stm32cube/bin/STM32_Programmer_CLI
                        STM32CubeProgrammer v2.2.0

Usage :
STM32_Programmer_CLI.exe [command_1] [Arguments_1][[command_2] [Arguments_2]...]

Testing the communication with the board

On the back of the board, there is a two-way DIP switch labeled SW1, which is used to configure the boot mode. When both are “ON”, the board boots from the SD card. When both are “OFF”, the board enters the “USB boot for flashing mode”, which is what we are going to use. So switch both switches to OFF, and reset the board.

Plug an additional USB-C cable from the board CN7 connector (which is located between the HDMI port and the 4 USB host ports).

USB-C connection for factory flashing

Then, reset the board. If you run lsusb on your Linux workstation, you should see a new device:

Bus 003 Device 011: ID 0483:df11 STMicroelectronics STM Device in DFU Mode

Then, you can ask STM32_Programmer_CLI to list the devices it sees over USB. This needs root permissions (unless appropriate udev rules are created):

$ sudo ~/stm32cube/bin/STM32_Programmer_CLI -l usb
                        STM32CubeProgrammer v2.2.0

=====  DFU Interface   =====

Total number of available STM32 device in DFU mode: 1

  Device Index           : USB1
  USB Bus Number         : 003
  USB Address Number     : 003
  Product ID             : DFU in HS Mode @Device ID /0x500, @Revision ID /0x0000
  Serial number          : 004200343338510534383330
  Firmware version       : 0x0110
  Device ID              : 0x0500

Good, the STM32CubeProgrammer tool is seeing our board, and we see that the Device Index is USB1. Keep that in mind for the next steps.

Change the Linux system boot chain

STM32CubeProgrammer works by sending a U-Boot bootloader over USB, and then talking to this U-Boot to make it erase the MMC or NAND flash, and make it write some data to those storage devices. However, for some reason, STM32CubeProgrammer doesn’t work with the boot flow we have used so far, which uses the U-Boot SPL as the first-stage bootloader, and U-Boot itself as the second stage bootloader. It only works when the first stage bootloader is the Arm Trusted Firmware, also called TF-A. You can get more details about the different possible boot chains on STM32MP1 on this Wiki page.

Due to this constraint, we are going to switch our Buildroot configuration to use TF-A instead of U-Boot SPL as the first stage bootloader.

First of all, we need to backport two Buildroot commits, which did not exist in the Buildroot 2019.02 we are using, but have been integrated later. The first commit, 9dbc934217e170578d4cbfdf524bc1b3988d0b9e allows to build TF-A for ARM 32-bit platforms, while the second commit, e4d276c357fdf9f19f99f826cab63f373687f902 allows to provide a custom name for the TF-A image name.

In Buildroot, do:

$ git cherry-pick 9dbc934217e170578d4cbfdf524bc1b3988d0b9e
$ git cherry-pick e4d276c357fdf9f19f99f826cab63f373687f902

The second one will cause some minor conflict in boot/arm-trusted-firmware/ Resolve the conflict by removing the BR2_TARGET_ARM_TRUSTED_FIRMWARE_DEBUG option from this file, remove the conflict markers, then run:

git add boot/arm-trusted-firmware/
git commit

If you’re not sure about this, you can check our 2019.02/stm32mp157-dk-blog-6 branch on Github, which has these changes already integrated.

Once done, we can run make menuconfig and start modifying the Buildroot configuration. Here are the changes that we need:

  • In the Bootloaders menu, enable ARM Trusted Firmware (ATF), and then:
    • Set ATF Version to Custom Git repository
    • Set URL of custom repository to
    • Set Custom repository version to v2.0-stm32mp-r2
    • Set ATF platform to stm32mp1
    • Set Additional ATF build variables to DTB_FILE_NAME=stm32mp157c-dk2.dtb AARCH32_SP=sp_min. The DTB_FILE_NAME selects the correct Device Tree file for the DK2 board, while the AARCH32_SP indicates that we are using the “minimal” secure payload, and not a complete Trusted Execution Environment such as OP-TEE.
    • Set Binary boot images to *.stm32. This makes sure the final image gets copied to output/images.
  • Still in the Bootloaders menu, inside the U-Boot option, make the following changes:
    • Change Board defconfig to stm32mp15_trusted. This is the most important change, which makes U-Boot build only the second stage, and in a format that gets loaded by TF-A as the first stage.
    • In U-Boot binary format, disable u-boot.img, and instead enable Custom (specify below) and indicate u-boot.stm32 as the value for U-Boot binary format: custom names.
    • Disable the Install U-Boot SPL binary image option.

Overall, the diff of the changes in the configuration looks like this:

@@ -30,16 +30,22 @@ BR2_TARGET_ROOTFS_EXT2=y
 # BR2_TARGET_ROOTFS_TAR is not set

Before we can restart the build, we need to adjust the genimage.cfg file that describes the layout of the SD card. Indeed, the file name of the first stage bootloader is now tf-a-stm32mp157c-dk2.stm32 instead of u-boot-spl.stm32 and the file name of the second stage bootloader is now u-boot.stm32 instead of u-boot.img. All in all, your genimage.cfg file in board/stmicroelectronics/stm32mp157-dk/genimage.cfg should now look like this:

image sdcard.img {
	hdimage {
		gpt = "true"

	partition fsbl1 {
		image = "tf-a-stm32mp157c-dk2.stm32"

	partition fsbl2 {
		image = "tf-a-stm32mp157c-dk2.stm32"

	partition ssbl {
		image = "u-boot.stm32"

	partition rootfs {
		image = "rootfs.ext4"
		partition-type = 0x83
		bootable = "yes"
		size = 256M

With this in place, it’s time to restart the build. You can do a complete rebuild with make clean all, or you can just clean up U-Boot, and restart the build:

$ make uboot-dirclean
$ make

You should now have in output/images the new TF-A image tf-a-stm32mp157c-dk2.stm32 and the new U-Boot image u-boot.stm32. Of course the sdcard.img file has been updated.

Rather than updating our SD card on our workstation, we’ll directly use the STM32CubeProgrammer tool to do that, in the next section.

Flashing the board

The STM32CubeProgrammer tool takes as input a flash layout file, which has a .tsv extension. The format of this file is extensively documented on this Wiki page. It is essentially a text file that says what should be flashed in each partition.

In our case, we are going to simply flash the entire sdcard.img instead of flashing partition by partition. To achieve this, we are going to use the RawImage image type, also described on the Wiki page.

Let’s create a file board/stmicroelectronics/stm32mp157-dk/flash.tsv, with the following contents:

#Opt	Id	Name	Type	IP	Offset	Binary
-	0x01	fsbl1-boot	Binary	none	0x0	tf-a-stm32mp157c-dk2.stm32
-	0x03	ssbl-boot	Binary	none	0x0	u-boot.stm32
P	0x10	sdcard	RawImage	mmc0		0x0	sdcard.img

The first line is a comment, just to help remember what each field is about. The second and third lines tell STM32CubeProgrammer which bootloader images should be used as part of the flashing process. Finally, the last line says we want to flash sdcard.img as a raw image on the mmc0 device.

Then, go do output/images, and run STM32CubeProgrammer. We use the -c port=usb1 argument, because our board was detected as device USB1 when we enumerated all detected devices using the -l usb previously.

$ cd output/images/
$ sudo ~/stm32cube/bin/STM32_Programmer_CLI -c port=usb1 -w ../../board/stmicroelectronics/stm32mp157-dk/flash.tsv

The output will look like this:

                        STM32CubeProgrammer v2.2.0                  

USB speed   : High Speed (480MBit/s)
Manuf. ID   : STMicroelectronics
Product ID  : DFU in HS Mode @Device ID /0x500, @Revision ID /0x0000
SN          : 004200343338510534383330
FW version  : 0x0110
Device ID   : 0x0500
Device name : STM32MPxxx
Device type : MPU
Device CPU  : Cortex-A7

Start Embedded Flashing service

Memory Programming ...
Opening and parsing file: tf-a-stm32mp157c-dk2.stm32
  File          : tf-a-stm32mp157c-dk2.stm32
  Size          : 237161 Bytes
  Partition ID  : 0x01 

Download in Progress:
[==================================================] 100% 

File download complete
Time elapsed during download operation: 00:00:00.444

RUNNING Program ... 
  PartID:      :0x01 
Start operation done successfully at partition 0x01

Flashlayout Programming ...
[==================================================] 100% 
Running Flashlayout Partition ...
Flashlayout partition started successfully

Memory Programming ...
Opening and parsing file: u-boot.stm32
  File          : u-boot.stm32
  Size          : 748042 Bytes
  Partition ID  : 0x03 

Download in Progress:
[==================================================] 100% 

File download complete
Time elapsed during download operation: 00:00:00.791

RUNNING Program ... 
  PartID:      :0x03 

reconnecting the device ...

USB speed   : High Speed (480MBit/s)
Manuf. ID   : STMicroelectronics
Product ID  : USB download gadget@Device ID /0x500, @Revision ID /0x0000
SN          : 004200343338510534383330
FW version  : 0x0110
Device ID   : 0x0500
Start operation done successfully at partition 0x03

Memory Programming ...
Opening and parsing file: sdcard.img
  File          : sdcard.img
  Size          : 539002368 Bytes
  Partition ID  : 0x10 

Download in Progress:
[==================================================] 100% 

File download complete
Time elapsed during download operation: 00:04:31.583

RUNNING Program ... 
  PartID:      :0x10 
Start operation done successfully at partition 0x10
Flashing service completed successfully

Finally, we can toggle back the SW1 DIP switches to their ON position, to boot again from SD card, and hit the reset button. The board should boot, but this time with our new image, which uses TF-A instead of U-Boot SPL, so the first lines of the boot process should look like this:

NOTICE:  Model: STMicroelectronics STM32MP157C-DK2 Discovery Board
NOTICE:  Board: MB1272 Var2 Rev.C-01
NOTICE:  BL2: v2.0-r2.0(release):
NOTICE:  BL2: Built : 16:10:53, Jan  7 2020
NOTICE:  BL2: Booting BL32
NOTICE:  SP_MIN: v2.0-r2.0(release):
NOTICE:  SP_MIN: Built : 16:10:53, Jan  7 2020

U-Boot 2018.11-stm32mp-r2.1 (Jan 07 2020 - 16:13:55 +0100)


In this article, we have discussed the concept of factory flashing, understood better the different boot chains available for the STM32MP1, switched to a boot chain using TF-A, and presented how to use STM32CubeProgrammer to reflash the entire SD card.

As usual, we have a branch on Github with the Buildroot changes corresponding to this blog post, see the branch 2019.02/stm32mp157-dk-blog-6.

Stay tuned for the next article in this series of blog post, in which we will cover the topic of Over-The-Air firmware update.

2019 at Bootlin, a year in review

First of all, the entire team at Bootlin wishes you a Happy New Year, and best wishes for 2020 in your personal and professional life. The beginning of the new year is a good time to look back and see the achievements of the past year, which is why we review the 2019 year in terms of Bootlin news and activity.

Linux kernel contributions

In 2019, we made contributions to Linux 5.0, Linux 5.1, Linux 5.2, Linux 5.3 and Linux 5.4. We contributed a total of 1078 patches to these releases.

Some of the highlights were:

  • The brand new subsystem to support the MIPI I3C bus that we developed from scratch was merged in Linux 5.0. This paved the way to support both I3C controllers and I3C devices in Linux. See our blog post.
  • The Marvell Ethernet controller driver was extended to support packet classification offloading in hardware.
  • A brand new driver in the IIO subsystem for the TI ADS8344 ADC chip.
  • Support for HW-accelerated H264 video decoding was added to the Allwinner VPU driver, as part of our crowd-funded project, see our recent blog post.
  • Numerous improvements in the support of Allwinner, Microchip and Marvell platforms, see our blog posts for each kernel release for more details.

Other contributions

  • We contributed 52 patches to the U-Boot project in 2019: a new network driver the Microsemi Ocelot platform, improvements to the MTD subsystem, fixes to the NXP LPC3250 and Rockchip PX30 platform support.
  • We contributed 314 patches to the Buildroot project, our most significant contribution is support for top-level parallel build, which will land in the upcoming Buildroot 2020.02 release. In addition, Bootlin engineer Thomas Petazzoni remains an active Buildroot co-maintainer: in 2019 he reviewed and merged 2924 patches from other contributors, out of the total of 5503 patches merged throughout the year.
  • We improved our Web-based Elixir code browser. Elixir now indexes the sources of 16 projects, allows to browse various types of include files, has support for project specific HTML post-processing filters, has a new REST API (thanks to Carmeli Tamir), and has many fixed bugs. All this activity corresponds to a round number of commits: 128.

Engineering projects

Of course, most of the contributions described above are driven by the engineering projects we have with our customers worldwide. Here are some of the significant engineering projects we worked on in 2019:

  • Implemented support for MACsec hardware offloading, and support for this functionality for the Microchip VSC8584 Ethernet PHY. We presented this work in detail in a blog post, and submitted 4 iterations in 2019 and hope to see this merged in early 2020.
  • Improved the Intel GMA500 display driver to support page flipping, so that one of our customers can use the Weston Wayland compositor on hardware platforms that use this display controller.
  • Started a project to support the Microchip VSC8572 Ethernet PHY in Linux, used as a pass-through to SFP cages. As part of this project, we already contributed patches to convert the cpsw network driver to phylink, and we will contribute VSC8572 patches once the project has made enough progress.
  • Migrated a complete Buildroot-based BSP for a Danish customer in the healthcare industry: migration to a newer Linux kernel version and a newer Buildroot version for a Microchip AT91SAM9G45 platform and a TI AM335x platform.
  • Migrated a complete Yocto-based BSP for a Belgian customer to a newer mainline version of the Linux kernel for an i.MX6 platform, implemented secure boot and optimized the boot time.
  • For a major US customer, implemented a complete Linux BSP for a custom Xilinx Zynq 7000 platform: upstream U-Boot, upstream Linux and Yocto-based build system. As part of this project, we did a number of kernel contributions and we still have a major kernel contribution pending: a complete DRM driver for the logiCVC display controller.
  • For a German customer in the healthcare industry, continued to support additional hardware features of an i.MX6 platform, and built a complete new BSP for an SAMA5D3-based hardware platform.
  • For a Canadian customer, completely upgraded the Linux BSP for a NXP LPC3250 platform: update to U-Boot upstream, to Linux upstream, and migration to Buildroot as a build system.
  • For an Italian customer, started a brand new BSP for a Rockchip PX30 based platform, which will require a number of improvements and additions to the Linux kernel support for this platform, which we will work on in 2020.
  • For a Belgian customer, migrated a Linux BSP for an OMAP44xx platform with complex audio interfaces to a recent upstream Linux kernel version.
  • For a French customer, implemented and delivered a complete Yocto-based Linux BSP for an i.MX6 platform.
  • For the French company Overkiz, updated, cleaned-up and upstreamed to the Linux kernel the Device Tree files for their Microchip SAMA5 home automation platforms.
  • Implemented support for software-based ECC and external hardware ECC engines in the SPI flash subsystem of the Linux kernel, for one of our customers that manufactures flash chips. This patch series is still under review, but we expect to get it merged in early 2020.
  • Implemented support for dm-verity and SELinux in OpenWRT, for one of our customers. See our blog post.
  • Continued to work on implementing top-level parallel build in Buildroot, which finally got merged at the end of 2019 in upstream Buildroot.
  • Continued to work on improving the support for Microchip ARM processors and Marvell Armada ARM processors in the Linux kernel, in many areas.
  • For a customer building a complex audio product based on an Allwinner system-on-chip, we implemented support for TDM in the Allwinner audio interface driver and used it in conjunction with PDM microphones.
  • Published a long series of blog posts on how to create a Linux system with Buildroot for the STM32MP1 platform: part 1, part 2, part 3, part 4 and part 5. This series will continue in 2020.
  • Completed the work on the Allwinner VPU that was funded by the Kickstarter campaign of early 2018: the Allwinner VPU driver was merged, with MPEG2, H264 and H265 decoding support, see our blog post.
  • Continued to work on the support for the RaspberryPi platforms, making a number of enhancements to the display support and its testing, as we reported in a blog post.


Our training business has seen quite a bit of activity in 2019:

  • We created and published a new training course: Displaying and rendering graphics with Linux. This 2-day course, created by Bootlin engineer Paul Kocialkowski provides a detailed walk-through of Linux graphics: graphics hardware and theory, low-level support in the Linux kernel, support in user-space in Wayland or, OpenGL acceleration, etc. This course is available on-site and we already delivered it to customers in Spain, Portugal and France.
  • Our Embedded Linux and Yocto/OpenEmbedded training courses have been ported to use the STM32MP1 platform for practical labs, and we became a member of the STMicroelectronics Partner Program. The support for STM32MP1 in our training courses is proposed as an alternative to the Microchip SAMA5D3 platform (for the Embedded Linux training) and the BeagleBone Black (for the Yocto training) that we continue to support as well.
  • Thanks to funding from Zuehlke Engineering in Serbia, we expanded our Linux boot time optimization training course to 3 days, adding much more lecture and lab content, and collecting useful benchmarks that we later shared in the Embedded Linux Conference Europe.
  • Overall our publicly available training materials have received 376 commits during the course of 2019, all visible in their GitHub repository.
  • We delivered many of our on-site training courses in France, India, Spain, Serbia, Poland, Finland, Portugal, Nederlands and Austria, and continued to offer our training courses in public sessions in Avignon, France.


As usual in 2019, we attended and participated to a number of conferences:

  • Our networking experts Antoine Ténart and Maxime Chevallier attended the Netdev 0x13 conference in Prague.
  • Bootlin engineer Alexandre Belloni attended the SiFive Tech Symposium about the RISC-V architecture, in Grenoble.
  • A significant part of our engineering team attended the Linux Plumbers conference in Lisbon.
  • Bootlin engineer Grégory Clement attended the Kernel Recipes conference in Paris.
  • Our display/video expert Paul Kocialkowski attended the Developers Conference, in Montreal.
  • And of course, we attended the Embedded Linux Conference Europe 2019. We gave 5 talks and 2 tutorials at this event (see our blog post) and shared our selection of talks.
  • We participated to the Capitole du Libre conference in Toulouse, where Michael Opdenacker gave a talk on Embedded Linux from scratch in 40 minutes (on RISC-V).
  • Participated to the Buildroot Developers Meeting throughout the year: after FOSDEM 2019 and before ELCE 2019. See our report from the FOSDEM meeting.
  • Recruiting

    • An additional engineer joined our team in Lyon: Kamel Bouhara. Kamel is now working with our senior engineers Grégory Clement and Alexandre Belloni in this office.
    • During the summer 2019, Victor Huesca joined Bootlin as an intern in Toulouse, and worked on improving the tooling used for the maintenance of the Buildroot project. All the work done by Victor is now used by the Buildroot community, see our blog post for more details.
    • An additional engineer will join our Toulouse office at the end of January 2020, and 3 interns will also join Bootlin during the first half of 2020, working on improving the Elixir Cross Referencer, and contributing to Linux and U-Boot.
    • We still have positions opened for Embedded Linux and kernel engineers, see job offer.

Wrapping up the Allwinner VPU crowdfunded Linux driver work

Back in early 2018, Bootlin started a crowd-funding campaign to fund the development of an upstream Linux kernel driver for the VPU found in Allwinner processors. Thanks to the support from over 400 contributors, companies and individuals, we have been able to bring support for hardware-accelerated video decoding in the mainline Linux kernel for Allwinner platforms.

From April 2018 to end of 2019, Paul Kocialkowski and Maxime Ripard at Bootlin worked hard on developing the driver and getting it accepted upstream, as well as developing the corresponding user-space components. We regularly published the progress of our work on this blog.

As of the end of 2019, we can say that all the goals defined in the Kickstarter have been completed:

  • We have an upstream Linux kernel for the Allwinner VPU, in drivers/staging/media/sunxi/cedrus, which supports MPEG2 decoding (since Linux 4.19), H264 decoding (since Linux 5.2) and H265 decoding (will be in the upcoming Linux 5.5)
  • We have a user-space VA-API implementation called libva-v4l2-request, and which allows to use any Linux kernel video codec based on the request API.
  • We have enabled the Linux kernel driver on all platforms we listed in our Kickstarter campaign: A13/A10S/A20/A33/H3 (since Linux 4.19), A64/H5 (since Linux 4.20), A10 (since Linux 5.0) and H6 (since Linux 5.1, contributed by Jernej Skrabec)

This means that the effort that was funded by the Kickstarter campaign is now over, and from now on, we are operating in maintenance mode regarding the cedrus driver: we are currently not actively working on developing new features for the driver anymore.

The Cedrus Linux driver in action

Of course, there are plenty of additional features that can be added to the driver: support for H264 encoding, support for high-profile H264 decoding, support for other video codecs. Bootlin is obviously available to develop those additional features for customers, do not hesitate to contact us if you are interested.

Overall, we found this experience of funding upstream Linux kernel development through crowd-funding very interesting and we’re happy to have been successful at delivering what was promised in our campaign. Looking at the bigger picture, the Linux userspace API for video decoding with stateless hardware codecs in V4L2 has been maturing for a while and is getting closer and closer to being finalized and declared a stable kernel API: this project has been key in the introduction of this API, as cedrus was the first driver merged to require and use it. Additional drivers are appearing for other stateless decoding engines, such as the Hantro G1 (found in Rockchip, i.MX and Microchip platforms) or the rkvdec engine. We are of course also interested in working on support for these VPUs, as we have gained significant familiarity with all things related to hardware video decoding during the cedrus adventure.