nixos-chromebook

A method of setting up audio, keyd, etc on NixOS.

I am not affiliated with Chrultrabook. Please don’t ask them for help regarding NixOS.

The self-built package may break due to compatibility for NixOS, issues may occur and this isn’t all perfect.

Prerequisites

Step 1: Create Configuration file(s)

Note that the configurations are applied to configuration.nix located in /etc/nixos.

Running the command sudo nixos-rebuild switch will rebuild your installation and apply the changes made.

First things first, for Chromebook-related configuration, we will create chrome-device.nix.

sudo touch /etc/nixos/chrome-device.nix

Then at the top of our configuration.nix we import chrome-device.nix.

# configuration.nix
# Edit this configuration file to define what should be installed on
# your system.  Help is available in the configuration.nix(5) man page
# and in the NixOS manual (accessible by running ‘nixos-help’).

{ config, pkgs, ... }:

{
  imports =
    [
      # Include the results of the hardware scan.
      ./hardware-configuration.nix
      ./chrome-device.nix
    ];

    # the rest of your configuration...
}

Step 2: ALSA UCM configuration

Build the package in chrome-device.nix and setup Keyd

# chrome-device.nix
{ config, pkgs, lib, ... }:

let
  cb-ucm-conf = with pkgs; alsa-ucm-conf.overrideAttrs {
    wttsrc = fetchFromGitHub {
      owner = "WeirdTreeThing";
      repo = "alsa-ucm-conf-cros";
      rev = "6b395ae73ac63407d8a9892fe1290f191eb0315b";
      hash = "sha256-GHrK85DmiYF6FhEJlYJWy6aP9wtHFKkTohqt114TluI=";
    };
    unpackPhase = ''
      runHook preUnpack
      tar xf "$src"
      runHook postUnpack
    '';

    installPhase = ''
      runHook preInstall
      mkdir -p $out/share/alsa
      cp -r alsa-ucm*/ucm2 $out/share/alsa
      runHook postInstall
    '';
  }; 
in
{
    services.keyd = {
    enable = true;
    keyboards.internal = {
      ids = [
        "k:0001:0001"
        "k:18d1:5044"
        "k:18d1:5052"
        "k:0000:0000"
        "k:18d1:5050"
        "k:18d1:504c"
        "k:18d1:503c"
        "k:18d1:5030"
        "k:18d1:503d"
        "k:18d1:505b"
        "k:18d1:5057"
        "k:18d1:502b"
        "k:18d1:5061"
      ];
      settings = {
        main = {
          f1 = "back";
          f2 = "forward";
          f3 = "refresh";
          f4 = "f11";
          f5 = "scale";
          f6 = "brightnessdown";
          f7 = "brightnessup";
          f8 = "mute";
          f9 = "volumedown";
          f10 = "volumeup";
          back = "back";
          forward = "forward";
          refresh = "refresh";
          zoom = "f11";
          scale = "scale";
          brightnessdown = "brightnessdown";
          brightnessup = "brightnessup";
          mute = "mute";
          volumedown = "volumedown";
          volumeup = "volumeup";
          sleep = "coffee";
        };
        meta = {
          f1 = "f1";
          f2 = "f2";
          f3 = "f3";
          f4 = "f4";
          f5 = "f5";
          f6 = "f6";
          f7 = "f7";
          f8 = "f8";
          f9 = "f9";
          f10 = "f10";
          back = "f1";
          forward = "f2";
          refresh = "f3";
          zoom = "f4";
          scale = "f5";
          brightnessdown = "f6";
          brightnessup = "f7";
          mute = "f8";
          volumedown = "f9";
          volumeup = "f10";
          sleep = "f12";
        };
        alt = {
          backspace = "delete";
          meta = "capslock";
          brightnessdown = "kbdillumdown";
          brightnessup = "kbdillumup";
          f6 = "kbdillumdown";
          f7 = "kbdillumup";
        };
        control = {
          f5 = "print";
          scale = "print";
        };
        controlalt = {
          backspace = "C-A-delete";
        };
      };
    };
  };

  # add your audio setup modprobes here

  environment = {
    systemPackages = [ pkgs.sof-firmware ];
    sessionVariables.ALSA_CONFIG_UCM2 = "${cb-ucm-conf}/share/alsa/ucm2";
    # AUDIO SETUP FOR < 23.11 AND UNSTABLE
  };

  # AUDIO SETUP FOR > 24.05

  system.replaceRuntimeDependencies = [
    ({
      original = pkgs.alsa-ucm-conf;
      replacement = cb-ucm-conf;
    })
  ];
}

The rest of this process varies between AVS and SOF. Pay attention to the # AUDIO SETUP FOR... comment(for your NixOS version), this will be replaced later in configuration.

Step 2A: Determine versions

You can check your NixOS channel with:

nix-channel --list

CPU generations to determine AVS or SOF for your Chromebook

AVS SOF
Skylake Alderlake
Kabylake Jasperlake
Apollolake Tigerlake
  Cometlake
  Geminilake
  Braswell
  Baytrail

If your CPU generation isn’t listed, please make a pull request!

Step 2B: Configuration based on Step 2A

SOF Configuration:

Depending on your NixOS verion, replace one of the comments in chrome-device.nix.

Replace # AUDIO SETUP FOR < 23.11 AND UNSTABLE with this if this comment applies to your NixOS version!

# chrome-device.nix
# for 23.11 and unstable
etc = {
  "wireplumber/main.lua.d/51-increase-headroom.lua".text = ''
      rule = {
        matches = {
          {
            { "node.name", "matches", "alsa_output.*" },
          },
        },
        apply_properties = {
          ["api.alsa.headroom"] = 4096,
        },
      }

    table.insert(alsa_monitor.rules,rule)
  '';
};

Replace # AUDIO SETUP FOR > 24.05 with this if this comment applies to your NixOS version!

# chrome-device.nix
in 
{
  # additonal configuration...

  # for 24.05
  services.pipewire.wireplumber.configPackages = [
    (pkgs.writeTextDir "share/wireplumber/main.lua.d/51-increase-headroom.lua" ''
      rule = {
        matches = {
          {
            { "node.name", "matches", "alsa_output.*" },
          },
        },
        apply_properties = {
          ["api.alsa.headroom"] = 4096,
        },
      }

      table.insert(alsa_monitor.rules,rule)
    '')
  ];

  # additonal configuration...
}

AVS Configuration:

Depending on your NixOS verion, replace one of the comments in chrome-device.nix.

Replace # AUDIO SETUP FOR < 23.11 AND UNSTABLE with this if this comment applies to your NixOS version!

# chrome-device.nix
# for 23.11 and unstable
etc = {
  "wireplumber/main.lua.d/51-avs-dmic.lua".text = ''
    rule = {
      matches = {
        {
          { "node.nick", "equals", "Internal Microphone" },
        },
      },
      apply_properties = {
        ["audio.format"] = "S16LE",
      },
    }

    table.insert(alsa_monitor.rules, rule)
  '';
};

Replace # AUDIO SETUP FOR > 24.05 with this if this comment applies to your NixOS version!

# chrome-device.nix
in 
{
  # additonal configuration...

  # for 24.05
  services.pipewire.wireplumber.configPackages = [
    (pkgs.writeTextDir "share/wireplumber/main.lua.d/51-avs-dmic.lua" ''
      rule = {
        matches = {
          {
            { "node.nick", "equals", "Internal Microphone" },
          },
        },
        apply_properties = {
          ["audio.format"] = "S16LE",
        },
      }

      table.insert(alsa_monitor.rules, rule)
    '')
  ];

  # additonal configuration...
}

Step 2C: Modprobes

This directly relies on what CPU generation you have

SOF modprobe config for Alderlake, Jasperlake, Tigerlake, Cometlake, and Geminilake

# chrome-device.nix
in
{
  boot = {
    extraModprobeConfig = ''
      options snd-intel-dspcfg dsp_driver=3
    '';
  };

  # additonal configuration...
}

SOF modprobe config for Braswell and Baytrail

# chrome-device.nix
in
{
  boot = {
    extraModprobeConfig = ''
      options snd-intel-dspcfg dsp_driver=3
      options snd-sof sof_debug=1
    '';
  };

  # additonal configuration...
}

AVS modprobe config for Skylake, Kabylake, and Apollolake

# chrome-device.nix
in
{
  boot = {
    extraModprobeConfig = ''
      options snd-intel-dspcfg dsp_driver=4
    '';
  };

  # additonal configuration...
}

Step 3: Post-Install

From here, you’ll need to rebuild your configuration

sudo nixos-rebuild switch

Changes should apply, you can reboot if necessary.

Feel free to see my configuration to see how I did all this!

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