From 15dc4c195a9a488c03b826ab612881906791076e Mon Sep 17 00:00:00 2001
From: Daniel Langbein <daniel@systemli.org>
Date: Thu, 23 Nov 2023 13:04:07 +0100
Subject: [PATCH] spin-down-hdd

---
 examples/case-esac.sh     | 13 +++++++++++++
 modules/spin-down-hdd.nix | 33 ++++++++++++++++++++++-----------
 2 files changed, 35 insertions(+), 11 deletions(-)
 create mode 100644 examples/case-esac.sh

diff --git a/examples/case-esac.sh b/examples/case-esac.sh
new file mode 100644
index 0000000..2b8fa5a
--- /dev/null
+++ b/examples/case-esac.sh
@@ -0,0 +1,13 @@
+#!/usr/bin/env bash
+set -eu -o pipefail
+
+x='some-test'
+
+case "${x}" in
+  *'_'*|*'-'*)
+    echo "The string contains _ or -"
+    ;;
+  *)
+    echo 'No pattern matched'
+    ;;
+esac
diff --git a/modules/spin-down-hdd.nix b/modules/spin-down-hdd.nix
index 9bc0b45..f4117f6 100644
--- a/modules/spin-down-hdd.nix
+++ b/modules/spin-down-hdd.nix
@@ -54,11 +54,6 @@
 #   # -i 120: Spin down after 2 minutes (120 seconds) of inactivity.
 #   ExecStart = "${pkgs.hd-idle}/bin/hd-idle -a /dev/disk/by-id/XXX-XXX-XXX -i 120";
 
-# Note about the `script` settings below.
-# If the disk is spun-down (in standby mode):
-# - The standby timeout has been set before already, otherwise it would be spinning.
-# - Don't set the standby timeout again, as this will spin up the disk.
-
 { lib, config, options, pkgs, modulesPath, ... }:
 with lib;
 let
@@ -77,11 +72,6 @@ in
   };
 
   config = mkIf (length cfg > 0) {
-    # TODO: Is this required or is it enough to use `${pkgs.hdparm}` in the systemd service script?
-    environment.systemPackages = with pkgs; [
-      hdparm
-    ];
-
     # For each element (e.g. "ata-WDC_WD40EFRX-68N32N0_WD-WCC7K0CPF0N1") in `cfg` create this config:
     #   systemd.services."hdparm-ata-WDC_WD40EFRX-68N32N0_WD-WCC7K0CPF0N1" = {
     #     description = ...;
@@ -95,7 +85,28 @@ in
         wantedBy = [ "multi-user.target" ];
         serviceConfig.Type = "oneshot";
         script = ''
-          ${pkgs.hdparm}/bin/hdparm -C /dev/disk/by-id/${id} | ${pkgs.busybox}/bin/grep 'standby' || ${pkgs.hdparm}/bin/hdparm -S 24 /dev/disk/by-id/${id}
+          set -eu -o pipefail
+          # Get IDE power mode status and remove any whitespace characters for easier pattern matching.
+          result="$(${pkgs.hdparm}/bin/hdparm -C /dev/disk/by-id/${id} | ${pkgs.coreutils}/bin/tr -d '[:space:]')"
+          case "''${result}" in
+            *'/dev/disk/by-id/${id}:drivestateis:standby'*|*'/dev/disk/by-id/${id}:drivestateis:sleeping'*)
+              printf '%s\n' 'Disk is in standby or sleeping.'
+              # Don't set idle timeout as this would spin up the disk.
+              # It has already been set before, otherwise the disk would be spinning.
+              ;;
+            *'/dev/disk/by-id/${id}:drivestateis:active/idle'*)
+              printf '%s\n' 'Disk is active. Set idle timeout to 10 minutes.'
+              ${pkgs.hdparm}/bin/hdparm -S 24 /dev/disk/by-id/${id}
+              ;;
+            *'/dev/disk/by-id/${id}:drivestateis:unknown'*)
+              printf '%s\n' 'Disk is not supported by hdparm.'
+              exit 1
+              ;;
+            *)
+              printf '%s%s\n' 'Unknown hdparm output: ' "''${result}"
+              exit 1
+              ;;
+          esac
         '';
       };
     }) cfg);