Marcus Folkesson

Embedded Linux Artist

Test packages in Buildroot

Test packages in Buildroot When writing packages for Buildroot there are several conditions that you have to test your package against. This includes different toolchains, architectures, C-libraries, thread-implementations and more. To help you with that, Buildroot provides the utils/test-pkg script. Nothing describes the script better than its own help text [1]: test-pkg: test-build a package against various toolchains and architectures The supplied config snippet is appended to each toolchain config, the resulting configuration is checked to ensure it still contains all options specified in the snippet; if any is missing, the build is skipped, on the assumption that the package under test requires a toolchain or architecture feature that is missing.

Posted by Marcus Folkesson on Tuesday, November 28, 2023

Git version in cmake

Git version in CMake All applications have versions. The version should somehow be exposed in the application to make it possible to determine which application we are actually running. I've seen a plenty of variants on how this is achieved, some are good and some are really bad. Since it's such a common thing, I thought I'd show how I usually do it. I use to let CMake determine the version based on git describe and tags, the benefit's that it is part of the build process (i.

Posted by Marcus Folkesson on Tuesday, November 14, 2023

Burn eFuses for MAC address on iMX8MP

Burn eFuses for MAC address on iMX8MP The iMX (iMX6, iMX7, iMX8) has a similiar OCOTP (On-Chip One Time Programmable) module that store, for example the MAC addresses for the internal ethernet controllers. The reference manual is not clear either on the byte order or which bytes belong to which MAC address when there are several. In fact, I had to look at the U-boot implementation [1] to know for sure how these fuses is used:

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Posted by Marcus Folkesson on Saturday, October 28, 2023

Loopback with two (physical) ethernet interfaces

Loopback with two (physical) ethernet interfaces Imagine that you have an embedded device with two physical ethernet ports. You want to verify the functionality of both these ports in the manufacturing process, so you connect an ethernet cable between the ports, setup IP addresses and now what? As Linux (actually the default network namespace) is aware of the both adapters and their IP/MAC-addresses, the system see no reason to send any traffic out.

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Posted by Marcus Folkesson on Saturday, October 21, 2023

kas-container and QEMU

kas-container and QEMU KAS KAS [1] is a setup tool for bitbake based projects such as Yocto. There are many similiar alternatives out there and I've tried most of them, but my absolute favorite is KAS. In order to use KAS, you have to setup a YAML file to contain information about your machine, distribution, meta layers and local configuration. Here is a small example configuration copied from the KAS documentation:

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Posted by Marcus Folkesson on Wednesday, October 18, 2023

Support for CRIU in Buildroot

Support for CRIU in Buildroot A couple of months ago I started to evaluate [1] CRIU [2] for a project I'm working on. The project itself is using Buildroot to build and generate the root filesystem. Unfortunately, Buildroot lacks support for CRIU so there were some work to do. To write the package was not straight forward. The package is only supported on certain architectures and the utils/test-pkg script failed for a few toolchains.

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Posted by Marcus Folkesson on Sunday, October 1, 2023

Use b4 for kernel contributions

Use b4 for kernel contributions There is a little tool called b4 [1] that has been part of my workflow with the Linux kernel for a while. It's developed to be a tool used to simplify the work of the maintainers, but my main use of the tool has been to fetch patch series from the mailing list and apply them to my local git repository during reviews. I recently noticed that it got a lot of handy features (experimental though) for the contributors as well, which I now want to test!

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Posted by Marcus Folkesson on Wednesday, August 23, 2023

Linux wireless regulatory domains

Linux wireless regulatory domains I had a case where I had an embedded system that should act as a WiFi Access Point on the 5GHz band. The HW was capable and the system managed to act as a client to 5GHz networks, so everything looked good. However, the system could not create an access point on some frequencies. How is it that? It's all about regulatory domains! Regulatory domains Radio regulations is something that applies to all devices that make transmissions in the radio spectrum.

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Posted by Marcus Folkesson on Monday, August 14, 2023

Add support for MCP39XX in Linux kernel

Add support for MCP39XX in Linux kernel I've maintained the MCP3911 driver in the Linux kernel for some time and continuously add support for new features [1] upon requests from people and companies. Microchip has several IC:s in this series of ADC:s that works similar to MCP3911. Actually, all other IC:s are register compatible but MCP3911. The IC:s I've extended support for is MCP3910, MCP3912, MCP3913, MCP3914, MCP3918 and MCP3919.

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Posted by Marcus Folkesson on Friday, August 4, 2023

Checkpoint-restore in Linux

Checkpoint-restore in Linux I'm working on power saving features for a project based on a Raspberry Pi Zero. Unfortunately, the RPi does not support features as hibernation to disk or suspend to RAM because how the processor is constructed (the GPU is actually the main processor). So I was looking for alternatives. That's when I stumpled upon CRIU ( [1], [2] ), Checkpoint-Restore In Userspace. (I actually started to read about PTRACE_SEIZE [4] and ptrace parasite code [3] and found out that CRIU is one of their users.

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Posted by Marcus Folkesson on Sunday, July 23, 2023