The UP Board family of platforms, developed by AAEON, is a series of compact, high-performance single-board computers (SBCs) widely used in the industry and embedded applications. They combine high-performance Intel processors with versatile I/O through a 40-pin Raspberry Pi-like header. At its core, an FPGA manages pin functionality, routing, and direction, enabling flexible use as I2C, UART, or GPIO. Supporting this setup in Linux is uniquely challenging and fascinating, and we were recently involved in bringing support for these I/Os upstream, successfully closing a story that had been open for seven years!
Congatec’s x86 System-on-Modules (SoM) include a Board Controller component connected to the processor via an eSPI bus, and providing various features such as I²C buses, GPIOs, a watchdog timer, and various sensors for monitoring voltage, fan speed, and more.
Conga-SA7 datasheet extract
For their x86 System-on-Modules (SoMs), Congatec provides a Yocto meta-layer: meta-congatec-x86. This meta-layer includes, among other components, a driver, a library, and tools for interfacing with the Board Controller.
The primary issue with the provided driver is its deviation from standard Linux APIs. It exposes a custom character device and relies on custom ioctl() for communication with userspace. This non-standard approach leads to compatibility and portability challenges. For example, an application using the standard Linux GPIO API would need to be adapted to access the GPIOs from Congatec’s Board Controller. Similarly, software designed specifically for the Board Controller’s GPIOs would require changes to work with GPIOs on other platforms.
Additionally, because the driver is out-of-tree, it raises concerns about long-term support and maintainability. Questions naturally arise—will the driver be regularly updated to remain compatible with future Linux kernel versions, given the instability of internal APIs? Will bugs and security vulnerabilities be addressed in a timely manner?
One of our customers, planning to use the Conga-SA7 board in a commercial product, recognized these challenges early on. As a result, they asked us to integrate support for the Congatec Board Controller directly into the mainline Linux kernel. Upstreaming the driver into the kernel would eliminate these issues by ensuring better portability, long-term maintenance, and community support.
Bootlin is happy to announce a new release of our OpenWrt feed openwrt-feed-st, which provides integration of ST’s STM32MP platforms with the OpenWrt build system. This new release openstlinux-6.1-openwrt-master-mpu-v24.06.26 updates the BSP software components and adds support for the new STM32MP2 platform.
The UP Board family of platforms, developed by AAEON, is a series of compact, high-performance single-board computers (SBCs) widely used in the industry and embedded applications. They combine high-performance Intel processors with versatile I/O through a 40-pin Raspberry Pi-like header. At its core, an FPGA manages pin functionality, routing, and direction, enabling flexible use as I2C, UART, or GPIO. Supporting this setup in Linux is uniquely challenging and fascinating, and we were recently involved in bringing support for these I/Os upstream, successfully closing a story that had been open for seven years!