Linux EVDI and Rolling Back Kernel Updates

I don't even know if I should be sharing this because I'm still unsure about what exactly happened, but I figured it was worth sharing, at least a little.

My main work desktop is an old Framework Laptop 13 mainboard running an 11th gen Intel i7-1165G7. I've got Debian 12 with KDE installed on it, which is not technically supported but has been chugging along just fine. Until recently.

Again, I'm not entirely sure what happened, but I think I did a kernel update from 6.1.0-22 to 6.1.0-23, and in turn, the EVDI driver wasn't able to build. Or something.

When I tried to run updates, I would get notified that the EVDI/DisplayLink drivers failed install. This wouldn't necessarily bother me, except that on reboot, my displays wouldn't work,^[1] so I needed to find a solution.

Anyway, I tried a few things, but I didn't really spend the time to understand the problem, and was tempted to just install Kubuntu (which I've got on my laptop) and be done with it, but I kept thinking if I could just change one thing it would be fine.

Basically, my system would detect that the DisplayLink drivers were out of date (or something) and would try to update the EVDI/DisplayLink drivers, but the EVDI drivers already existed in the DKMS tree, and failed to build properly.

I didn't record all the errors or logs, but here's an example of the outputs I did save:

Error: Installation has failed. If you'd like to file a bug report please include '/var/log/nala/dpkg-debug.log'
Error! Bad return status for module build on kernel: 6.1.0-23-amd64 (x86_64) 
Consult /var/lib/dkms/evdi/1.14.6/build/make.log for more information. 

Error: error processing package evdi (--configure): installed evdi package post-installation script subprocess returned error exit status 10

and some more:

...
Raw = False: [b'Error! DKMS tree already contains: evdi-1.14.6\r\nYou cannot add the same module/version combo more than once.\r\n'] Data_Split = [b'Error! DKMS tree already contains: evdi-1.14.6', b'You cannot add the same module/version combo more than once.', b'']
...

Anyway, I asked ChatGPT for help and used it as a framework^[2] to to troubleshoot. I'll summarize the steps we tried below:

1. Purge^[3] drivers
   1. sudo nala purge evdi displaylink-driver
   2. sudo nala autoremove
   3. Completed successfully
2. Remove the EVDI driver from the kernel
   1. sudo dkms remove evdi/1.14.6 --all
3. Install current linux headers
   1. sudo nala install build-essential linux-headers-$(uname -r)
   2. Failed with errors similar to above

After a while, ChatGPT recommended I roll back my kernel version. For some reason I didn't realize this was an option, and so I removed the current Kernel and installed the most recent.

I ran uname -r to find out which kernel I was running, which was linux-image-6.1.0-23-amd64. At the time of writing, this appears to be the latest image, based on this page^[4], which had linux-image-6.1.0-23-amd64 listed.

I also used the Debian Package Tracker to try to find the latest package by searching for the name, but only found unsigned and dbg versions, so I figured I would revert.

sudo nala purge linux-image-6.1.0-23-amd64 linux-headers-6.1.0-23-amd64 evdi displaylink-driver
sudo nala autoremove

This gave me a warning that uninstalling the current kernel would prevent me from booting, so I told it to continue, and installed version 22:

sudo nala install linux-image-6.1.0-22-amd64 linux-headers-6.1.0-22-amd64

Then I rebooted, confirmed I was in 22 with uname -r, and it seemed to be fine!

While I was writing this up, however, I found that update 23 was supposed to be a stable release and a security update, so I wanted to apply again and see if anything broke.

sudo nala install linux-image-6.1.0-23-amd64 linux-headers-6.1.0-23-amd64

Reboot, no issues; check for updates, also no issues. So maybe the original kernel install had a problem, and I needed to reinstall it to get working again? I dunno, still unclear. Just thought someone might find this helpful.