1 files changed, 54 insertions, 0 deletions
diff --git a/nixos/modules/tasks/scsi-link-power-management.nix b/nixos/modules/tasks/scsi-link-power-management.nix
new file mode 100644
index 00000000000..a9d987780ee
--- /dev/null
+++ b/nixos/modules/tasks/scsi-link-power-management.nix
@@ -0,0 +1,54 @@
+{ config, lib, ... }:
+
+with lib;
+
+let
+
+  cfg = config.powerManagement.scsiLinkPolicy;
+
+  kernel = config.boot.kernelPackages.kernel;
+
+  allowedValues = [
+    "min_power"
+    "max_performance"
+    "medium_power"
+    "med_power_with_dipm"
+  ];
+
+in
+
+{
+  ###### interface
+
+  options = {
+
+    powerManagement.scsiLinkPolicy = mkOption {
+      default = null;
+      type = types.nullOr (types.enum allowedValues);
+      description = ''
+        SCSI link power management policy. The kernel default is
+        "max_performance".
+        </para><para>
+        "med_power_with_dipm" is supported by kernel versions
+        4.15 and newer.
+      '';
+    };
+
+  };
+
+
+  ###### implementation
+
+  config = mkIf (cfg != null) {
+
+    assertions = singleton {
+      assertion = (cfg == "med_power_with_dipm") -> versionAtLeast kernel.version "4.15";
+      message = "med_power_with_dipm is not supported for kernels older than 4.15";
+    };
+
+    services.udev.extraRules = ''
+      SUBSYSTEM=="scsi_host", ACTION=="add", KERNEL=="host*", ATTR{link_power_management_policy}="${cfg}"
+    '';
+  };
+
+}