Enabling concurrent mode with rtl88x2bu

Help
1

I am trying to enable concurrent mode feature of this driver as mentioned here:
https://github.com/morrownr/88x2bu-20210702/blob/ecf5014fe0f9f0ee87f84ea2b7472da788fd8627/docs/Concurrent_Mode.md

In order to do this you have to execute a script “./cmode_on.sh” after unpacking the source, but before building.

I have successfully added the module and it works perfectly without concurrent mode, but NixOS handles all the building in the background so I am unsure how to tell NixOS to activate the feature during the install.

I have been reading through the manual, but I am new to NixOS and I cannot tell what would be the correct “Nix way” to do this.

Any help would be much appreciated.

2

So as far at I see the current NixOs package does not provide any option to turn it on https://github.com/NixOS/nixpkgs/blob/8ff7b290e6dd47d7ed24c6d156ba60fc3c83f100/pkgs/os-specific/linux/rtl88x2bu/default.nix (see also https://github.com/NixOS/nixpkgs/blob/a0bb254735ab64192ea1eb55aac524e4d4973501/pkgs/top-level/linux-kernels.nix#L389)

Or the other hand, the cmode-on script is trivial: it just updates a flag in the Makefile https://github.com/morrownr/88x2bu-20210702/blob/ecf5014fe0f9f0ee87f84ea2b7472da788fd8627/cmode-on.sh#L15

So I would say that for a quick fix the simplest is to add an overlay that replaces the rtl88x2bu package with your own, that would be a copy/paste of the above (or, cleaner, use overrideAttr to still receive updates if you want) except that you add a prePatch phase that either run the cmode-on script (but you would need to patch it first as it links to /bin/bash) or, simpler, to directly replace the flag in the Makefile by copy/pasting the sed command, or, cleaner, to use substituteInPlace offered by nix.

If you want I can try to provide you the code. Just not very handy now from my phone.

3

Actually if you use

boot.kernelModules = [ "88x2bu" ];
boot.extraModulePackages = [
  config.boot.kernelPackages.rtl88x2bu
];

To load the packages, you don’t even need overlays. You should be able to just replace it with (sorry not tested I’m on the phone):

boot.kernelModules = [ "88x2bu" ];
boot.extraModulePackages = [    
  (config.boot.kernelPackages.rtl88x2bu.overrideAttrs (old: {
    prePatch = old.prePatch + ''
      substituteInPlace Makefile --replace "CONFIG_CONCURRENT_MODE = n" "CONFIG_CONCURRENT_MODE = y"
    '';
  }))
];

Edit: added old.prePatch + …

4

Thank you so much for responding!

This was the right path.

I did have to make a slight modification. Apparently there were existing prePatch commands which needed to be in place for the driver to build so I had to append instead of replace it. Here is what ended up working.

boot.extraModulePackages = [    
  (config.boot.kernelPackages.rtl88x2bu.overrideAttrs (old: {
    prePatch = old.prePatch + ''
      substituteInPlace Makefile --replace "CONFIG_CONCURRENT_MODE = n" "CONFIG_CONCURRENT_MODE = y"
    '';
  }))
];

I rebooted after the rebuild completed and now i have two wifi devices!

Thanks so much!

1 Like
5

Oh good point, I forgot to check if prePatch was not already used ^^ I edited my answer to avoid having broken code here. If you want, you can maybe contribute to nixpkgs to add this option as a simple override (just add an optional argument in the derivation file and add the above code conditionally). I’m sure it could be helpful to others.

6

I will see about making that contribution. I have been looking to get into contributing to open source projects and this seems like a good simple first step.

1 Like