nix-config/modules/nixos/hardware/raspberry-pi/config.nix

# This file is a modified version of config.txt generator
# Licensed under the terms of MIT License
# https://raw.githubusercontent.com/nix-community/raspberry-pi-nix/refs/heads/master/rpi/config.nix
# with modifications
# https://raw.githubusercontent.com/nvmd/raspberry-pi-nix/refs/heads/master/rpi/config.nix

{ lib, config, pkgs, namespace, ... }:
let
  cfg = config.${namespace}.hardware.raspberry-pi;

  render-raspberrypi-config = let

    render-kvs = kvs: let
      render-kv = k: v:
        if isNull v.value then k
        else "${k}=${toString v.value}";
    in lib.attrsets.mapAttrsToList render-kv
        (lib.filterAttrs (k: v: v.enable) kvs);

    render-dt-param = x: "dtparam=" + x;
    render-dt-params = params:
      lib.strings.concatMapStringsSep "\n" render-dt-param (render-kvs params);

    render-dt-overlay = { overlay, params }:
      lib.concatStringsSep "\n" (lib.filter (x: x != "") [
        ("dtoverlay=" + overlay)
        (render-dt-params params)
        "dtoverlay="
      ]);

    render-options = opts:
      lib.strings.concatStringsSep "\n" (render-kvs opts);

    render-base-dt-params = render-dt-params;

    render-dt-overlays = overlays:
      lib.strings.concatMapStringsSep "\n" render-dt-overlay
        (lib.attrsets.mapAttrsToList
          (overlay: params: {
            inherit overlay;
            inherit (params) params;
          })
          (lib.filterAttrs (k: v: v.enable) overlays));

    render-config-section = conditionalFilter:
      { options, base-dt-params, dt-overlays }:
      let all-config = lib.concatStringsSep "\n" (lib.filter (x: x != "") [
          (render-options options)
          (render-base-dt-params base-dt-params)
          (render-dt-overlays dt-overlays)
        ]);
      in ''
        [${conditionalFilter}]
        ${all-config}
      '';
  in conf: lib.strings.concatStringsSep "\n"
      ((lib.attrsets.mapAttrsToList render-config-section conf)
      ++ [ cfg.extra-config ]);
in {
  options.${namespace}.hardware.raspberry-pi = {
    config = let
      rpi-config-param = {
        options = {
          enable = lib.mkEnableOption "attr";
          value = lib.mkOption {
            type = with lib.types; oneOf [ int str bool ];
          };
        };
      };
      dt-param = {
        options = {
          enable = lib.mkEnableOption "attr";
          value = lib.mkOption {
            type = with lib.types; nullOr (oneOf [ int str bool ]);
            default = null;
          };
        };
      };
      dt-overlay = {
        options = {
          enable = lib.mkEnableOption "overlay";
          params = lib.mkOption {
            type = with lib.types; attrsOf (submodule dt-param);
            default = {};
          };
        };
      };
      raspberry-pi-config-options = {
        options = {
          options = lib.mkOption {
            type = with lib.types; attrsOf (submodule rpi-config-param);
            default = { };
            description = ''
              Common hardware configuration options, translates to
              `<option>=<value>` in the `config.txt`.
              <https://www.raspberrypi.com/documentation/computers/config_txt.html#common-hardware-configuration-options>
            '';
            example = {
              arm_boost = { # arm_boost=1
                enable = true;
                value = true;
              };
            };
          };
          base-dt-params = lib.mkOption {
            type = with lib.types; attrsOf (submodule dt-param);
            default = { };
            description = ''
              Parameters to pass to the base DTB, translates to
              `dtparam=<param>=<value>` in the `config.txt`.
              <https://www.raspberrypi.com/documentation/computers/configuration.html#part3.2>
            '';
            example = {
              i2c = { # dtparam=i2c=on
                enable = true;
                value = "on";
              };
              ant2 = {  # dtparam=ant2
                enable = true;
              };
            };
          };
          dt-overlays = lib.mkOption {
            type = with lib.types; attrsOf (submodule dt-overlay);
            default = { };
            description = ''
              DTB overlays to enable and configure with parameters, translates to
              ```
               dtoverlay=<overlay>
               dtparam=<param>=<value>
               dtoverlay=
              ```, which is an equivalent to a more popular format of
              `dtoverlay=<overlay>,<param>=<value>`.
              <https://www.raspberrypi.com/documentation/computers/configuration.html#part3.1>
            '';
            example = {
              vc4-kms-v3d = { # dtoverlay=vc4-kms-v3d,cma-256
                enable = true;
                params = {
                  cma-256 = {
                    enable = true;
                    # value = "";
                  };
                };
              };
              disable-bt = {  # dtoverlay=disable-bt
                enable = true;
              };
            };
          };
        };
      };
    in lib.mkOption {
      type = with lib.types; attrsOf (submodule raspberry-pi-config-options);
      description = ''
        Configures `config.txt` file for Raspberry Pi devices.
        The file is located on a firmware partition, usually mounted at
        `/boot/firmware`.
        <https://www.raspberrypi.com/documentation/computers/config_txt.html>
      '';
    };

    extra-config = lib.mkOption {
      type = lib.types.lines;
      default = "";
      description = ''
        Extra options that will be appended to `/boot/firmware/config.txt` file.
        For possible values, see: https://www.raspberrypi.com/documentation/computers/config_txt.html
      '';
    };

    config-generated = lib.mkOption {
      type = lib.types.str;
      description = ''
        The config file text generated by hardware.raspberry-pi.config
      '';
      readOnly = true;
    };
  };

  config = {
    hardware.raspberry-pi.config-generated = render-raspberrypi-config cfg.config;
  };
}