alien: enable and use i2c and ddcutil

home/tiling/niri/scripts/brightness.sh

@@ -1,5 +1,4 @@
 #!/usr/bin/env bash
-
 WAYBAR_SIGNAL=8   # SIGRTMIN+8
 
 if [ "$#" -ne 1 ]; then
@@ -15,15 +14,33 @@ if ! [[ "$value" =~ ^-?[0-9]+$ ]] || [ "$value" -lt -100 ] || [ "$value" -gt 100
     exit 1
 fi
 
-# Apply brightness change with correct syntax
+# Determine which brightness control tool to use
-if [ "$value" -gt 0 ]; then
+if command -v ddcutil >/dev/null 2>&1; then
-    brightnessctl s "+${value}%" >/dev/null
+    # Get current brightness
-elif [ "$value" -lt 0 ]; then
+    current=$(ddcutil getvcp 10 | grep -oP 'current value =\s+\K\d+')
-    brightnessctl s "${value#-}%-" >/dev/null
+
+    if [ -z "$current" ]; then
+        echo "Error: failed to read current brightness from ddcutil" >&2
+        exit 1
+    fi
+
+    # Calculate new brightness (ddcutil uses absolute 0-100 scale)
+    new=$((current + value))
+
+    # Clamp to valid range
+    [ "$new" -lt 0 ] && new=0
+    [ "$new" -gt 100 ] && new=100
+
+    # Set new brightness
+    ddcutil setvcp 10 "$new" >/dev/null 2>&1
 else
-    : # no-op for 0
+    # Fallback to brightnessctl
+    if [ "$value" -gt 0 ]; then
+        brightnessctl s "+${value}%" >/dev/null
+    elif [ "$value" -lt 0 ]; then
+        brightnessctl s "${value#-}%-" >/dev/null
+    fi
 fi
 
 # Notify Waybar to refresh
 pkill -RTMIN+"$WAYBAR_SIGNAL" waybar
-

system/hosts/alien/default.nix

@@ -10,6 +10,18 @@
 {
   networking.hostName = "alien";
 
+  environment.systemPackages = with pkgs; [
+    pkgs.ddcutil
+    pkgs.mangohud
+  ];
+
+  # enable ddcutil
+  users.users.sckova.extraGroups = [ "i2c" ];
+  boot.initrd.kernelModules = [ "i2c-dev" ];
+  services.udev.extraRules = ''
+    KERNEL=="i2c-[0-9]*", GROUP="i2c", MODE="0660"
+  '';
+
   boot.binfmt.emulatedSystems = [
     "aarch64-linux"
     "riscv64-linux"
@@ -62,7 +74,6 @@
   };
 
   environment = {
-    systemPackages = [ pkgs.mangohud ];
     loginShellInit = ''
       [[ "$(tty)" = "/dev/tty1" ]] && ./gs.sh
     '';