* If power management is enabled, set the governor to ‘ondemand’ by

default.  See
  
    http://www.codon.org.uk/~mjg59/power/good_practices.html
    
  for the reasoning.  (Basically, the ‘performance’ and ‘powersave’
  governors don't actually provide extra performance or power savings
  in most cases.)

  It used to be that desktop environments like KDE were able to set
  the governor through HAL (e.g. KDE could be configured to switch to
  the powersave governor when the user unplugs his laptop).  However,
  this is no longer the case with upower — it is now expected that
  everybody uses the ondemand governor.  See

    http://old.nabble.com/-PATCH--powerdevil-remove-cpufreq.patch-td27815354.html

* Rename ‘cpuFreqGovernor’ to ‘powerManagement.cpuFreqGovernor’.

* Include cpufreq-utils in the system path if a governor is set, since
  we depend on it anyway.

svn path=/nixos/trunk/; revision=30991

modules/config/power-management.nix

@@ -91,6 +91,8 @@ in
         "p4_clockmod"
       ];
 
+    powerManagement.cpuFreqGovernor = "ondemand";
+
   };
 
 }

modules/tasks/cpu-freq.nix

@@ -6,7 +6,8 @@ with pkgs.lib;
   ###### interface
 
   options = {
-    cpuFreqGovernor = mkOption {
+  
+    powerManagement.cpuFreqGovernor = mkOption {
       default = "";
       example = "ondemand";
       description = ''
@@ -15,13 +16,17 @@ with pkgs.lib;
         "userspace".
       '';
     };
+    
   };
 
 
   ###### implementation
 
-  config = mkIf (config.cpuFreqGovernor != "") ({
-    jobs.cpuFreq =
+  config = mkIf (config.powerManagement.cpuFreqGovernor != "") {
+
+    environment.systemPackages = [ pkgs.cpufrequtils ];
+
+    jobs.cpufreq =
       { description = "Initialize CPU frequency governor";
 
         startOn = "started udev";
@@ -30,10 +35,11 @@ with pkgs.lib;
 
         script = ''
           for i in $(seq 0 $(($(nproc) - 1))); do
-            ${pkgs.cpufrequtils}/bin/cpufreq-set -g ${config.cpuFreqGovernor} -c $i
+            ${pkgs.cpufrequtils}/bin/cpufreq-set -g ${config.powerManagement.cpuFreqGovernor} -c $i
           done
         '';
       };
-  });
+      
+  };
 
 }