This is a continuation of my previous post about upgrading the old 2.6.28 Linux kernel that came with my Chumby 8. In that post, I got a modern U-Boot working with SD card support, which is what I needed in order to boot Linux.
After I finished getting U-Boot working, I began work on the kernel. I based my work on the stable kernel version 5.15.33. I started by compiling a kernel using the bundled pxa168_defconfig file. I created a device tree file called pxa168-chumby8.dts based on pxa168-aspenite.dts. It needed a few tweaks. I specified the correct amount of RAM for the Chumby 8 (128 MB) and changed the model and compatible strings. I also disabled “twsi1” which is an I2C host. I wasn’t ready to deal with I2C yet. Here’s a small snippet of the relevant changed parts of my new device tree file.
As I mentioned in my last post, I spent a good chunk of my spare time over the past 6 months working on a project I’ve been thinking about for over a decade. I bought a Chumby 8 in 2011. It’s an 8″ touchscreen device powered by the Marvell PXA166 processor. It is essentially a souped-up digital picture frame with extra capabilities like speakers, a microphone, and Wi-Fi. There are a bunch of little Flash-based “apps” you can install for stuff like pictures, music, sports scores, weather, games, etc. I have no idea how many of the apps still work these days. Chumby actually went out of business a few months after I bought mine, although one of the founders stepped up to keep the service running. A variant of this device was also created for Insignia, which was called the Infocast 8″ Internet Media Display.
I was never really interested in using it for any of the stock functionality. I thought it would be a fun development platform. It would be exciting to make some custom apps in Qt or something. One thing that was a little frustrating was that it came with a Linux 2.6.28 “Erotic Pickled Herring” kernel circa Christmas 2008, which was ancient even at the time I bought it. This is a pretty common issue with Linux-based devices. I will even admit I’ve been responsible for some old kernels out in the field in Internet-connected devices. I don’t blame Chumby. It’s tough when the SoC vendor doesn’t submit their kernel modifications upstream or at least keep their fork up to date. I’ve been there.
I’ve been doing some Linux kernel development in my spare time over the past 6 months or so. The goal has been to get my old Chumby 8 (stock kernel 2.6.28) running on a modern kernel with custom firmware. It has been going really well and there have been lots of fun problems I’ve needed to solve along the way. I may write some posts about that process if there is any interest. It’s been a blast.
Anyway, I thought it would also be fun to jump into the current craze of OpenAI’s ChatGPT free research preview and apply it to Linux kernel development. Let’s see just how well this AI can write a basic kernel module that I describe. Can it improve the module as I ask it to make tweaks?
I started out by asking:
Write a Linux kernel module that prints “Hello world” to the console every 5 seconds. Also provide a Makefile for compiling it.
