Quirk with new nixos integration

[umbrageodotus]

Hey!

Somehow, removing "KBUILD_OUTPUT=${kernel.dev}/lib/modules/${kernel.modDirVersion}/build" from kernelModuleMakeFlags when kernel packages already has it (https://github.com/NixOS/nixpkgs/blob/master/pkgs/top-level/linux-kernels.nix#L356) makes it not build...? Is it because i'm using chaotic-nyx's cachyos kernel?

Thanks,
Alex <3

[AndyFilter]

Hey, like I said in the last Nix related PR (#42), I don't know anything about Nix, thus I don't feel comfortable involving myself in this. All I can do is forward this issue to @kitten, so maybe they can look into this at their earliest convenience.

[kitten]

I mean, I don't think this sounds like an issue? More like a question that's ... just floating around 😅 I don't quite know why KBUILD_OUTPUT is still needed. It used to be part of the regular boilerplate of creating a kernel module in Nix. I still see it often referenced. It's unclear to me what the build scripts are like and why the output needs to be defined in this target in this way.

That said, what's the problem here if the Nix code's build for Yeetmouse works? 😅

[umbrageodotus]

No problem, just a weird quirk. Especially since upstream drivers don't need KBUILD_OUTPUT anymore (I believe).

[AndyFilter]

So... I'm not gonna pretend like I know what's going on in the NixOs's kernel development space, but can this issue be closed?
I don't know if there were any updates to this from the NixOs maintainers or something, so I don't want to close this issue, but please consider closing it if nothing more can be added to this conversation.
Thanks!

[umbrageodotus]

The root cause wasn't yet found...

[delet-this]

It seems like that the package gets kernelModuleMakeFlags from the default value pkgs.linuxPackages.kernelModuleMakeFlags and not the actual system kernel, so KBUILD_OUTPUT is set to a path that matches that specific package set. The kernel the package gets does match the actual kernel though, not quite sure why. While concatenating the correct KBUILD_OUTPUT value does work, I don't think it's ideal and I feel like other mismatching flags in kernelModuleMakeFlags could also cause problems. I could try to take a better look at this later.

edit: Seems like we'd want to import the package using config.boot.kernelPackages.callPackage within a nixos module in order to get kernelModuleMakeFlags, but yeah I'll try to take a look later.