Use systemd unit to create AMD uprof device

m/module/amd-uprof.nix

@@ -22,23 +22,28 @@
     # Make the userspace tools available in $PATH.
     environment.systemPackages = with pkgs; [ amd-uprof ];
 
-    # Add extra udev rules to setup the /dev/AMDPowerProfiler device. They
+    # The AMDPowerProfiler module doesn't create the /dev device nor it emits
-    # forgot to add these.
+    # any uevents, so we cannot use udev rules to automatically create the
-    services.udev.extraRules = let
+    # device. Instead, we run a systemd unit that does it after loading the
-      # To create the device node we need to read the device number from the
+    # modules.
-      # /proc directory, so the module must have been loaded first.
+    systemd.services.amd-uprof-device = {
-      addDevice = pkgs.writeShellScript "add-amd-uprof-dev.sh" ''
+      description = "Create /dev/AMDPowerProfiler device";
-        set -x
+      after = [ "systemd-modules-load.service" ];
-        echo date > /tmp/uprof.log
+      wantedBy = [ "multi-user.target" ];
-        mknod /dev/AMDPowerProfiler -m 666 c $(< /proc/AMDPowerProfiler/device) 0
+      unitConfig.ConditionPathExists = [
-      '';
+          "/proc/AMDPowerProfiler/device"
-      removeDevice = pkgs.writeShellScript "remove-amd-uprof-dev.sh" ''
+          "!/dev/AMDPowerProfiler"
-        rm /dev/AMDPowerProfiler
+      ];
-      '';
+      serviceConfig = {
-    in
+        Type = "oneshot";
-      ''
+        RemainAfterExit = true;
-        KERNEL=="AMDPowerProfiler", SUBSYSTEM=="module", ACTION=="add", RUN+="${addDevice}"
+        ExecStart = pkgs.writeShellScript "add-amd-uprof-dev.sh" ''
-        KERNEL=="AMDPowerProfiler", SUBSYSTEM=="module", ACTION=="remove", RUN+="${removeDevice}"
+          mknod /dev/AMDPowerProfiler -m 666 c $(< /proc/AMDPowerProfiler/device) 0
-      '';
+        '';
+        ExecStop = pkgs.writeShellScript "remove-amd-uprof-dev.sh" ''
+          rm -f /dev/AMDPowerProfiler
+        '';
+      };
+    };
   };
 }