nixos support for nvidia optimus

currently, only support for fully disabling nvidia is provided, which
is helpful for saving power/heat.

In the future, this should be extended so we can choose:

- nvidia only  (choose between nouveau/nvidia driver)
- IGP only
- Hybrid (choose between nouveau/nvidia driver, use the "bumblebee" package/daemon)

svn path=/nixos/trunk/; revision=32085

modules/module-list.nix

@@ -70,6 +70,7 @@
   ./services/hardware/acpid.nix
   ./services/hardware/bluetooth.nix
   ./services/hardware/hal.nix
+  ./services/hardware/nvidia-optimus.nix
   ./services/hardware/pcscd.nix
   ./services/hardware/sane.nix
   ./services/hardware/udev.nix

modules/services/hardware/nvidia-optimus.nix

@@ -0,0 +1,40 @@
+{pkgs, config, ...}:
+
+let kernel = config.boot.kernelPackages;
+in
+
+{
+
+  ###### interface
+
+  options = {
+
+    hardware.nvidiaOptimus.disable = pkgs.lib.mkOption {
+      default = false;
+      type = pkgs.lib.types.bool;
+      description = ''
+        completely disable the nvidia gfx chip (saves power / heat) and just use IGP
+      '';
+    };
+
+  };
+
+
+  ###### implementation
+
+  config = pkgs.lib.mkIf config.hardware.nvidiaOptimus.disable {
+    boot.blacklistedKernelModules = ["nouveau" "nvidia" "nvidiafb"];
+    boot.kernelModules = [ "bbswitch" ];
+    boot.extraModulePackages = [ kernel.bbswitch ];
+
+    jobs.bbswitch = {
+      name = "bbswitch";
+      description = "turn off nvidia card";
+      startOn = "stopped udevtrigger";
+      exec = "discrete_vga_poweroff";
+      path = [kernel.bbswitch];
+      task = true;
+    };
+  };
+
+}