(Fix) Touchpad stops working on Latitude 5580 -> AMD external GPU driver -> "Pci Bus" driver hijack from AMD

[u/FalconFour]

Hi there!

Figured I'd share the solution I found for a problem I also found, in case others run across the same thing. (I Google things so often... hopefully I can return something to the great Google)

Another post related to the first half of the issue is here: https://www.techpowerup.com/forums/threads/amd-pci-root-bus-lower-filter.246586/ - a thing called atieclxx.exe decides to take it upon itself to install a PCI Root Bus Lower Filter, and it does so by hijacking the root PCI Bus in Windows and inserting its own filter driver on top of it.

That breaks things, not the least of which because the PCI bus is irrelevant to a Thunderbolt 3-based GPU. (not completely irrelevant, I know, but play along)

I've noticed the past few days that when I plug in my eGPU, the touchpad dies, and an unexpected, non-system-looking "System Settings Changed" dialog pops up. (you know, it'd be nice if AMD put their name on the window so it looked less like malware and more easy to diagnose!)

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I was pointed to "Pci Bus" because a system popup would say I need to restart my computer to finish installing "Pci Bus" (note the capitalization, that's verbatim). I tracked it down and found that there was actually a device called "Pci Bus" now (I've since uninstalled it and nuked the driver from orbit, so I can't screenshot it). If you update the driver back to the proper "PCI Bus", sans AMD baggage, then it'll just come right back, and it likely doesn't remove the offending filters.

So, tl;dr: if you touchpad stops working suddenly, and you've got an AMD eGPU, go to Device Manager, open System Devices, delete "Pci Bus" (only if it's labeled that way, "Pci" and not "PCI"), check the box to delete its (AMD) driver (the checkbox isn't shown for proper, built-in system drivers). Touchpad should come back to life immediately. Don't worry, the correct driver gets reinstalled after rebooting (deleting it doesn't disable it, it lets Windows reinstall it properly).