liminix/modules/kernel.nix

## Kernel-related options
## ======================
##
##

{ lib, pkgs, config, ...}:
let
  inherit (lib) mkEnableOption mkOption types isDerivation hasAttr ;
  inherit (pkgs.pseudofile) dir symlink;
  inherit (pkgs.liminix.networking) address interface;
  inherit (pkgs.liminix.services) bundle;
  inherit (pkgs) liminix;

  type_service = pkgs.liminix.lib.types.service;

  mergeConditionals = conf : conditions :
    # for each key in conditions, if it is present in conf
    # then merge the associated value into conf
    lib.foldlAttrs
      (acc: name: value:
        if (conf ? ${name}) && (conf.${name} != "n")
        then acc // value
        else acc)
      conf
      conditions;
in {
  options = {
    kernel = {
      src = mkOption { type = types.path; } ;
      version = mkOption { type = types.str; default = "5.15.137";} ;
      modular = mkOption {
        type = types.bool;
        default = true;
        description = "support loadable kernel modules";
      };
      extraPatchPhase = mkOption {
        default = "true";
        type = types.lines;
      };
      config = mkOption {
        description = ''
          Kernel config options, as listed in Kconfig* files in the
          kernel source tree. Do not include the leading "CONFIG_"
          prefix when defining these.  Most values are "y", "n" or "m",
          but sometimes other strings are also used.
        '';
        type = types.attrsOf types.nonEmptyStr;
        example = lib.literalExpression ''
          {
            BRIDGE = "y";
            TMPFS = "y";
            FW_LOADER_USER_HELPER = "n";
          };
        '';
      };
      conditionalConfig = mkOption {
        description = ''
          Kernel config options that should only be applied when
          some other option is present.
        '';
        type = types.attrsOf (types.attrsOf types.nonEmptyStr);
        default = {};
        example = {
          USB = {
            USB_XHCI_MVEBU = "y";
            USB_XHCI_HCD = "y";
          };
        };
      };
      makeTargets = mkOption {
        type = types.listOf types.str;
      };
    };
  };
  config = {
    system.outputs =
      let
        mergedConfig = mergeConditionals
          config.kernel.config
          config.kernel.conditionalConfig;
        k = liminix.builders.kernel.override {
          config = mergedConfig;
          version = builtins.trace config.kernel.version config.kernel.version;
          inherit (config.kernel)  src extraPatchPhase;
          targets = config.kernel.makeTargets;
        };
      in {
        kernel = k.vmlinux;
        zimage = k.zImage;
      };

    kernel = rec {
      modular = true; # disabling this is not yet supported
      makeTargets = ["vmlinux"];
      config = {
        IKCONFIG = "y";
        IKCONFIG_PROC = "y";
        PROC_FS = "y";

        KEXEC = "y";
        MODULES = if modular then "y" else "n";
        MODULE_SIG = if modular then "y" else "n";
        DEBUG_FS = "y";

        # basic networking protocols
        NET = "y";
        UNIX = "y";
        INET = "y";
        IPV6 = "y";
        PACKET = "y";           # for ppp, tcpdump ...
        SYSVIPC= "y";

        NETDEVICES = "y";       # even PPP needs this

        # disabling this option causes the kernel to use an "empty"
        # initramfs instead: it has a /dev/console node and not much
        # else.  Note that pid 1 is started *before* the root
        # filesystem is mounted and it expects /dev/console to be
        # present already
        BLK_DEV_INITRD = lib.mkDefault "n"; # overriden by initramfs module

        # s6-linux-init mounts this on /dev
        DEVTMPFS = "y";
        # some or all of these may be fix for "tmpfs: Unknown parameter 'mode'" error
        TMPFS = "y";
        TMPFS_POSIX_ACL = "y";
        TMPFS_XATTR = "y";

        FW_LOADER = "y";
        FW_LOADER_COMPRESS = "y";
        # We don't have a user helper, so we get multiple 60s pauses
        # at boot time unless we disable trying to call it.
        # https://lkml.org/lkml/2013/8/5/175
        FW_LOADER_USER_HELPER = "n";
      };
    };
  };
}