Linux kernel 2.6.29 – New features for embedded users

Tuz Linux logoThe 2.6.29 version of the Linux kernel has just been released by Linus Torvalds. Like all kernel releases, this new version offers a number of interesting new features.

For embedded users, the most important new feature is certainly the inclusion of Squashfs, a read-only compressed filesystem. This filesystem is very well-suited to store the immutable parts of an embedded system (applications, libraries, static data, etc.), and replaces the old cramfs filesystem which had some strong limitations (file size, filesystem size and limited compression).

Squashfs is a block filesystem, but since it is read-only, you can also use it on flash partitions, through the mtdblock driver. It’s fine as you just write the filesystem image once. Don’t hesitate to try it to get the best performance out of your flash partitions. Ideally, you should even use it on top of UBI, which would transparently allow the read-only parts of your filesystem to participate to wear-leveling. See sections about filesystems in our embedded Linux training materials for details.

This new release also adds Fastboot support, at least for scsi probes and libata port scan. This is a step forward to reducing boot time, which is often critical in embedded systems.

2.6.29 also allows stripping of generated symbols under CONFIG_KALLSYMS_ALL, saving up to 200 KB for kernels built with this feature. This is nice for embedded systems with very little RAM, which still need this feature during development.

Another new feature of this kernel is the support for the Samsung S3C64XX CPUs. Of course, a lot of new boards and devices are supported, such as the framebuffer of the i.MX 31 CPU, or the SMSC LAN911x and LAN912x Ethernet controllers.

The other major features of this new kernel, not necessarily interesting for embedded systems are the inclusion of the btrfs filesystem, the inclusion of the kernel modesetting code, support for WiMAX, scalability improvements (support of 4096 CPUs!), filesystem freezing capability, filesystem improvements and many new drivers.

For more details on the 2.6.29 improvements, the best resource is certainly the human-readable changelog written by the KernelNewbies.org community.

The Buildroot project begins a new life

The Buildroot project has been around for a quite a while. For those just discovering Buildroot, it is a set of Makefiles that ease and automate the process of building a cross-compilation toolchain (based on the uClibc C library, since Buildroot has been initiated by uClibc developers) and a full embedded Linux system. Buildroot can compile over 600 packages : graphical libraries (Qt Embedded, Gtk, X.org, DirectFB), network servers (the Dropbear SSH server, several HTTP servers), and more), core components such as Busybox, DBUS, Avahi and many other free software packages that make sense on embedded systems. Of course, more packages can easily be added. Buildroot is very similar to PTXdist.

I remember using to this project and contributing to it back in 2004 when I still was an intern during my studies. One of my contributions was the writing of documentation for the project, which is still the official documentation. Since 2004, the project has evolved, but there was no clear maintainer and no stable releases. The developer community around Buildroot was not completely satisfied since no one was merging the proposed fixes and improvements, since there was no official maintainer. And Buildroot was difficult to use for users because it didn’t offer any kind of stable releas : users had to pick a random SVN checkout and cross fingers to get a reasonably-working version.

In January 2009, as part of the traditionnal new year’s resolution, Peter Korsgaard, one of the most active Buildroot developers, volunteered to step up as the official maintainer and to deliver releases. And indeed, he integrated many patches that were floating around, released several release candidates before releasing Buildroot 2009.02 on February, 12th. Since then he continues to make very interesting improvements to Buildroot, replies on the mailing list, review and merge the proposed patches. A new bug tracker has been set up, and the source code will soon be moved over the Git distributed version control system.

Definitely, it’s a new life starting for the Buildroot project. As a long-time user and occasional contributor of the project, I’m glad to see such evolution.

FOSDEM 2009 videos

As previously announced, I had the chance to attend the FOSDEM conference again this year. And once again, the famous Bootlin video camera was with me, and I could record a few talks. I’m pleased to make them available today.

FOSDEM, the Free and Open Source Software Developers' European Meeting

Here are the available videos, with my personal comments. Of course, except the talk about CMake, all of them come from the embedded devroom. Thanks to the speakers for sharing their knowledge and presenting their projects !

  • video captureWt, a C++ web toolkit, for rich web interfaces to embedded systems, by Pieter Libin (Noesis Solutions)
    Video (44 minutes, 124M)
    Presentation of a Web application generator, which generates a Web application including a web server from a C++ description. The C++ design is based on many ideas coming from Qt, which eases the creation of the graphical application. Certainly a very interesting tool for embedded systems.
  • Hacking with modular hardware: the BUG, by Ken Gilmer (Bug Labs)
    Video (43 minutes, 129M)
    The BUG is a set of hardware modules that can be combined together. A base module contains the CPU, memory and other basic components, while additional modules can provide GPS, Wifi, webcam, I/O lines and many others. Of course, it comes with a completely free software SDK. Can be an interesting starting point for prototyping or hobbyist embedded hacking, even though the hardware is quite expensive.
  • Building Embedded Linux Systems with PTXdist, by Robert Schwebel (Pengutronix)
    Video (68 minutes, 151M)
    A very good presentation on why system building tools are needed for Embedded Linux systems (cross-compiling issues, etc.), and how PTXdist fits this need. Even though I’m personally quite fan of Buildroot, PTXdist’s competitor, the presentation was very interesting.
  • video captureDevelopment on the OpenMoko with hackable:1, by Pierre Pronchery (Bearstech)
    Video (55 minutes, 189M)
    A hands-on lab on the OpenMoko, which unfortunately was too short to be really interesting, and restricted to only the 10-12 people at the front of the room. Interesting for the people who did it, probably not so interesting to watch afterwards.
  • Development and Certification of Linux-Based Fire Safety & Security Systems, by Baurzhan Ismagulov (Siemens)
    Video (47 minutes, 124M)
    The topic of the talk was really appealing, because the use of free software in environments where human life is in danger has always caused many debates and discussions. Unfortunately, the talk completely misses the point : the speaker spent the whole talk discussing Germany-specific rules and laws for the certification of fire safety and security systems, almost without saying a word on how Linux can match these rules.
  • Maemo on BeagleBoard, by Juha Kallionen (Nokia)
    Video (20 minutes, 51M)
    Good talk, but not a lot of content, outside of « Hey, we run Maemo on BeagleBoard, try it !». A kind of announcement talk, I would say.
  • video captureAdvanced power management for OMAP3, by Peter De Schrijver (Nokia)
    Video (49 minutes, 169M)
    A very interesting, in-depth, technical talk about the power management features of the OMAP3 CPU and how these features can be used by the Linux kernel.
  • Emdebian 1.0 release – small and super small Debian, by Neil Williams (Debian)
    Video (86 minutes, 257M)
    video captureAgain, another interesting talk about the status of Emdebian, which has just reached 1.0. Neil described both Emdebian Crush and Emdebian Grip, that are two different approaches for making Debian more suitable for embedded systems. Very good progress has been made, and Emdebian is certainly something that should now be considered as a distribution for embedded systems.
  • CMake – what can it do for your project, by Alexander Neundorf
    Video (45 minutes, 167M)
    A general introduction to CMake, with lots of examples and demonstrations. Very nice for those who never had the opportunity to look at CMake.

USB-Ethernet device for Linux

Useful device when you work with an embedded development board

For our Embedded Linux training sessions, I was looking for a USB to Ethernet device. Since Linux supported devices are often difficult to find, I’m glad to share my investigations here.

When you use an embedded development board, you must connect it to your computer with an Ethernet cable, for example to transfer a new kernel image to U-boot through tftp, or to make your board boot on a directory on your workstation, exported with NFS.

You could connect both the board and computer to your local network, which would still allow your computer to connect to the Internet while you work with the board. However, you may create conflicts on your local network if you don’t use DHCP to assign an IP address to your board (if your DHCP server even accepts this new device on the network). In a training environment, you are also likely to run out of Ethernet outlets in the training room if you have to connect 8 such boards. Hence, a direct connection between the board and your workstation’s Ethernet port is often the most convenient solution.

If you can’t use WIFI to keep your computer connected to the outside world, a good solution is to add an extra Ethernet port to your computer by using an USB-to-Ethernet device.

My colleague Thomas and I started looking for such devices that would be supported by Linux. Here are a few that we found:

  • D-Link DUB-E100. Supported by the USB_NET_AX8817X driver. However, this product is bulky and quite heavy (at least 100 grams).
  • TRENDnet TU2-E100. Supported by the same driver, but still bulk (August 2015 update: now replaced by a more recent version, now almost as small as the Apple one, and supported out of the box in Linux. See the comment about this device.)
  • Linksys USB 200m. Supported by the same Linux driver and has a much more acceptable size, but customer reviews complain that its connector can break easily.
  • Apple USB Ethernet Adapter. This should be working out of the box in Linux. At least the MB442Z/A or MC704ZM/A references did, but Apple now sells a new reference that might have a different chipset. It is beautiful, small and light. Support for this device (at least the references I mentioned) was added to Linux 2.6.26 through the same driver. You should be able to use it in recent distros.

Apple USB to EthernetSo, I recommend the Apple device. I event posted a comment on the Apple Store, titled “Perfect for Linux”! I hope the Apple droids won’t censor it. Don’t hesitate to buy it, so that we can confirm that the latest reference is supported too.

I can’t tell whether this could happen with Apple. This was the first Apple device I ever bought…

Program for Embedded Linux Conference 2009 announced

CELF penguinThe program for the Embedded Linux Conference 2009 has been announced a few days ago, and the registration is now open. For the record, the Embedded Linux Conference is probably the largest technical conference specifically dedicated to the use of Linux on embedded systems. Organized by the CE Linux Forum every year, this conference gathers a large audience and a wide range of very interesting talks.

The 2009 edition of ELC will take place from April 6th to April 8th, in downtown San Francisco, in the United States.

The program features :

  • Almost 50 talks, tutorials and keynotes. The topics go from multimedia, flash filesystems, system initialization, memory management, instrumentation and debugging tools, real-time, embedded distributions, system building,
  • An opening keynote by Dirk Hohndel from Intel
  • A keynote by David Woodhouse, one of the two embedded Linux maintainers
  • Other famous speakers such as Paul Mundt (maintainer of the Linux port to the SuperH architecture), Kate Alhola (from Maemo/Nokia), Dan Malek (from Embedded Alley), Mike Anderson (the PTR group, famous for his JTAG tutorial), Jake Edge (from LWN), Klaas van Gend (from Montavista), Frank Rowand (from Sony, famous for his real-time adventures talk), Jim Ready, Denis Oliver Kropp (DirectFB main developer)
  • A panel on The Linux Kernel, what’s next with Jonathan Corbet, Greg KH, Andrew Morton, Keith Packard and Ted Ts’o
  • And last but not least, a talk from Michael Opdenacker, Bootlin, on flash filesystems.

Of course, both Michael and I will attend the conference. Hope to meet you there!
Golden Gate Bridge

Public session changes

New agenda, sessions in Grenoble, and walking away with an embedded board

Did you notice? We’ve made significant changes to our next public training sessions.

First of all, partnering with CALAO Systems, we are opening new public sessions in Grenoble.

In the upcoming sessions, we also offer a new training agenda, covering embedded Linux system development in full detail. Until recently, our public trainings dedicated approximately 3 days to kernel integration and device driver development, and only 2 days to real-time and to developing the system itself. The new sessions will still cover kernel configuration, (cross)compiling and usage, but will leave Linux kernel and driver development to dedicated sessions.

The new training sessions will thus cover the below topics:

  • Introduction to embedded Linux
  • Bootloaders
  • Configuring, (cross)compiling and booting a Linux kernel
  • Block filesystems
  • Flash filesystems – Manipulating flash partitions
  • C library and cross-compiling toolchains
  • Embedded system development tools
  • BusyBox and other lightweight tools for embedded systems. Graphical toolkits
  • Debugging and profiling tools
  • Implementing realtime requirements
  • Udev and hotplugging
  • System optimizations
  • Practical lab: implementing a multimedia system

CALAO SystemsFor the first time too, each participant will walk away with an embedded board from CALAO systems. After the training sessions, you will then be able to go on practicing with the new technologies that you discovered, and to build your own system prototypes.

You will find more details in the description of our public training sessions.

If there is enough demand, we will propose other public sessions in September 2009, this time on Linux kernel and device driver development. Don’t hesitate to contact us if you are interested in such a session. We could even make it earlier if enough people are interested.

Real hardware in our training sessions

At last, real hardware in our training sessions

If you haven’t had a look at our new training agendas, you may not have noticed that we now use real hardware in our embedded Linux and kernel training sessions. For 4 years, we had been using the QEMU emulator on the x86, arm and mips platforms. While this simplified training session logistics, and avoided any trouble due to hardware failures, this was not close enough to the real world situations that our customers face.

Calao's logoWe chose the nifty boards from Calao Systems. They have great features that make them very attractive for training and prototyping purposes

  • AT91SAM9263 ARM CPU from ATMEL, running at 200 MHz
  • 64 MB of RAM and 256 MB of flash, which are more than enough for any embedded system we can think of.
  • Small and light (30 g), with a USB connector replacing power, serial and JTAG connectors, making it easy to travel with several of these devices without having to carry many heavy accessories. Carrying convenience was a key decision factor.
  • 100 Mbit Ethernet port, allowing to practice with root filesystems on NFS, and with tftp from the U-boot command line.
  • CALAO USB 92632 USB 2.0 host ports, allowing to connect any type of device. In particular, we are thinking about USB mass storage and webcam devices.
  • 1 USB device port, allowing to experiment with Linux USB gadget drivers.
  • Very affordable price (less than 160 €).

On the software side, this board is also very attractive:

  • It is supported by the mainline Linux kernel, since version 2.6.27.
  • A bricked board can be reflashed without ever needing to use Windows, thanks the Linux version of Atmel’s SAM-BA utility.
  • It will soon be supported by the mainline version of U-boot. We are contributing to this.
  • It should also be directly supported in the mainline version of Buildroot in the next months, making it easy to build complete root filesystems for it. We will also work on this.

We will also soon offer training cost options that include these boards. This way, customers can walk away with their own device and easily continue to practice with the training hardware and make prototypes, without having to go through an extra purchasing process.

Call for presentations for the LSM embedded track

The Libre Software Meeting (LSM) is an annual event on free software taking place in july in France since 2000. The LSM meeting is organized this year in Nantes, France from 7th to 11th July. Amongst several tracks, the Libre Software Meeting will feature an « Embedded Systems and Open Hardware » track, for which the call for presentations has been released recently.

The purpose of the “Embedded Systems and Open Hardware” session is to give the state of the art of free software for embedded systems and Open Hardware. Technical topics of this session include but are not limited to:

  • Embedded OS Development kernel architecture, implementation and port for embedded systems
  • Embedded Development Tools: tool chains and project cases (tool chain projects, packaging for cross compilation, portability …)
  • Embedded Linux: µClinux…
  • Real-time extensions for Linux: RTLinux, RTAI…
  • Hard real-time kernels: eCos, RTEMS, ADEOS, Xenomai…
  • Soft Real-time kernels
  • Embedded Java
  • GUI for embedded systems: Gtk, Qt, Nano/X…
  • Linux and System on Chip (SoC)
  • Open Hardware, Open design, free IP modules (Intellectual Property) and softcores: opencores, OpenRISC, NIOS, Microblaze, LEONSparc, FPGA…

The conference will last 30 minutes, questions included. Round tables will be organized. Synthetic presentations are scheduled to last 20 minutes. PDF versions of the presentation are not mandatory but they will be greatly appreciated (with an online web access just after the LSM event, they are a very useful documentation source for the entire community).

If you plan to participate and to propose a presentation, please send a message as soon as possible to the following address: embarque@rmll.info with a summary of your presentation (and if you can, a summary in English too) no later than 15th march 2009. Feel free to forward this Call For Presentation to other places or to everyone you think could be interested.

Embedded Linux Conference Europe 2008 videos

Together with the announcement of our free mainlining offer in our Linux kernel and bsp development services, we are pleased to announce the availability of new conference videos.

The CELF Embedded Linux Conference Europe (ELCE) and the NLUUG Autumn Conference on Mobile Computing took place last November in Ede, in the Netherlands.

For those who don’t know them yet, the Embedded Linux Conference (ELC) and ELCE are in our opinion the most interesting conferences for embedded Linux system developers. They cover only interesting topics, such as power management, boot time, flash storage, security, graphics, mobile applications and many more.

This time, four people shot videos: Ruud Derwig (NXP), Tim Bird (Sony), Thomas Petazzoni and Michael Opdenacker (both from Bootlin). Then, Thomas took care of reading the tapes and DVDs, and encoding them to Ogg/Theora, all this in just a few minutes of manual intervention, thanks to his super automated scripts.

Here are all the videos:

Speakers were supposed to post their slides on the CELF Wiki, but some of them haven’t done it yet.

If you don’t know which video to start with, here are the talks that Thomas Petazzoni and I preferred:

Of course, these are just our personal recommendations, from the talks we managed to attend. We are sure that many other ones are worth recommending.

Kernel and BSP development and mainlining

Offering free mainlining for Linux kernel, device driver and BSP development

Note: Due to the number of requests we get for mainlining work, we can no longer continue the offer described below.

Bootlin is best known worldwide for its kernel and embedded Linux system training sessions and its free training materials, and also perhaps for sharing videos from technical conferences.

However, did you know that Bootlin is not a training company?

We are actually embedded Linux system and kernel developers like the people we support, train and work for. This is essential to be good trainers, in addition to our passion for sharing what we learn. For example, have you ever had a look at the description of our engineering services?

In our training activity, we differentiate with other suppliers by offering custom sessions, being completely transparent with our training materials, costs and customer evaluations. Here’s how we can also make a difference in our development activity:

  • As in all our activities, by focusing only on the Linux kernel, device drivers, bootloaders, embedded and real-time system development.
  • By offering free mainlining to any customer who orders Linux board support packages or Linux device drivers from us. Having our code accepted in the official Linux and U-boot sources brings terrific benefits to our customers and can be a key contributor to the success of their products.
  • By working inside the Linux development community. Being part of it, we know this community very well: its people, its rules, its best practices and its best resources. This helps us to make the right decisions (if needed, collecting advice from the right people), and quickly obtain the expected results.