Allow using deckbd for password entry during boot

modules/devices/steamdeck/default.nix

@@ -16,6 +16,7 @@ in
   imports = [
     ./controller.nix
     ./fan-control.nix
+    ./fde.nix
     ./firmware.nix
     ./graphical.nix
     ./hw-support.nix

modules/devices/steamdeck/fde.nix

@@ -0,0 +1,105 @@
+{ config, lib, pkgs, utils, ... }:
+
+let
+  cfg = config.jovian.devices.steamdeck;
+in
+{
+  options = {
+    jovian.devices.steamdeck = {
+      fde = {
+        deckbd = {
+          enable = lib.mkOption {
+            default = cfg.enable;
+            defaultText = lib.literalExpression "config.jovian.devices.steamdeck.enable";
+            type = lib.types.bool;
+            description = ''
+              Whether to enable deckbd for initrd password entry.
+
+              You may need hold the option key for a second before entering your
+              password.
+            '';
+          };
+          bindsTo = lib.mkOption {
+            inherit (utils.systemdUtils.unitOptions.commonUnitOptions.options.bindsTo) type;
+            description = ''
+              systemd units that require deckbd.
+
+              For example, if you want controller input in unl0kr, add `config.boot.initrd.systemd.services.unl0kr-ask-password.name`.
+
+              Plymouth and the console work by default.
+            '';
+          };
+          debug = lib.mkOption {
+            default = false;
+            type = lib.types.bool;
+            description = ''
+              Enable debug output for deckbd.
+
+              This will log keycodes to the journal.
+            '';
+          };
+        };
+      };
+    };
+  };
+
+  config = lib.mkMerge [
+    (lib.mkIf cfg.fde.deckbd.enable {
+      assertions = [
+        {
+          assertion = cfg.enableDefaultStage1Modules;
+          message = ''
+            deckbd cannot be used without the required kernel modules.
+
+            jovian.devices.steamdeck.enableDefaultStage1Modules must be enabled.
+          '';
+        }
+        {
+          assertion = config.boot.initrd.systemd.enable;
+          message = ''
+            deckbd requires systemd-in-initrd.
+
+            boot.initrd.systemd.enable must be set to true. Note that this may impact other NixOS features.
+          '';
+        }
+      ];
+
+      jovian.devices.steamdeck.fde.deckbd.bindsTo = [
+        "systemd-ask-password-console.service"
+        (lib.mkIf config.boot.plymouth.enable config.systemd.services.systemd-ask-password-plymouth.name)
+        # Note: Agents that have optional keyboard input, such as unl0kr, should not be added here. The user may not want it.
+      ];
+
+      boot.initrd = {
+        kernelModules = [ "uinput" ];
+
+        services.udev.packages = [
+          (pkgs.writeTextDir "lib/udev/rules.d/70-steam-deck-controller.rules" ''
+            ACTION=="add", SUBSYSTEM=="input", ENV{ID_VENDOR_ID}=="28de", ENV{ID_MODEL_ID}=="1205", ENV{PRODUCT}=="?*", ENV{ID_INPUT_JOYSTICK}=="1", TAG+="systemd", ENV{SYSTEMD_ALIAS}+="/sys/class/input/input_steam_deck_controller"
+          '')
+        ];
+
+        systemd = {
+          storePaths = with pkgs; [ deckbd ]; # https://github.com/NixOS/nixpkgs/issues/309316
+          services.deckbd = {
+            description = "Steam Deck controller keymapper";
+            unitConfig.DefaultDependencies = false;
+            wantedBy = cfg.fde.deckbd.bindsTo;
+            before = cfg.fde.deckbd.bindsTo;
+            inherit (cfg.fde.deckbd) bindsTo;
+            requires = [ "sys-class-input-input_steam_deck_controller.device" ];
+            after = [ "sys-class-input-input_steam_deck_controller.device" ];
+            path = with pkgs; [ deckbd ];
+            environment.G_MESSAGES_DEBUG = lib.mkIf cfg.fde.deckbd.debug "all";
+            # Note: The lizard_mode parameter does not work as intended. The
+            # Steam Deck must also be manually put into gamepad mode by holding
+            # the option key for a second.
+            preStart = "echo 0 > /sys/module/hid_steam/parameters/lizard_mode";
+            script = "deckbd";
+            postStop = "echo 1 > /sys/module/hid_steam/parameters/lizard_mode";
+          };
+        };
+      };
+    })
+  ];
+}

modules/devices/steamdeck/hw-support.nix

@@ -46,6 +46,7 @@ in
 
         # Gamepad
         "usbhid"
+        "hid-steam"
       ];
       boot.initrd.availableKernelModules = [
         "nvme"

overlay.nix

@@ -93,4 +93,6 @@ rec {
 
   decky-loader = final.callPackage ./pkgs/decky-loader { };
   decky-loader-prerelease = final.callPackage ./pkgs/decky-loader/prerelease.nix { };
+
+  deckbd = final.callPackage ./pkgs/deckbd { };
 }

pkgs/deckbd/default.nix

@@ -0,0 +1,33 @@
+{ lib
+, stdenv
+, fetchFromGitHub
+, pkg-config
+, glib
+, libevdev
+}:
+
+stdenv.mkDerivation {
+  pname = "deckbd";
+  version = "0-unstable-2024-07-01";
+
+  src = fetchFromGitHub {
+    owner = "Ninlives";
+    repo = "deckbd";
+    rev = "1d2c71f2c096fbfa42624dd820a9d11a35c64826";
+    hash = "sha256-Svp/5Mo/XkiptbTM3E4QhSRxC6rMeF0t3eTq9BUjLbs=";
+  };
+
+  nativeBuildInputs = [ pkg-config ];
+
+  buildInputs = [ glib libevdev ];
+
+  makeFlags = [ "PREFIX=$(out)" ];
+
+  meta = {
+    description = "Steam Deck controller keymapper";
+    homepage = "https://github.com/Ninlives/deckbd";
+    license = lib.licenses.gpl3Only;
+    mainProgram = "deckbd";
+    platforms = lib.platforms.linux;
+  };
+}