Support reloading btusb module after resuming

dell/xps/sleep-resume/bluetooth/default.nix

@@ -0,0 +1,40 @@
+{config, lib, pkgs, ...}:
+
+let
+  inherit (lib) mkIf mkOption types;
+
+  reloadBtusb = pkgs.writeShellApplication {
+    name = "reload-btusb.sh";
+    runtimeInputs = [
+      pkgs.coreutils
+      pkgs.kmod
+    ];
+    text = ''
+      # Reload Bluetooth after resuming from sleep.
+
+      # Wait up-to 0.5 second for the module to be unloaded:
+      # (It should never take this long)
+      modprobe -r --wait 500 btusb
+
+      # "btusb" sometimes seems to need a little bit of time to settle after unloading:
+      sleep 0.2
+      modprobe btusb
+    '';
+  };
+
+  cfg = config.services.sleep-resume.bluetooth;
+in {
+  options = {
+    services.sleep-resume.bluetooth = {
+      enable = mkOption {
+        default = false;
+        type = types.bool;
+        description = "Reload Bluetooth after resuming from sleep";
+      };
+    };
+  };
+
+  config = mkIf cfg.enable {
+    powerManagement.resumeCommands = "${reloadBtusb}/bin/reload-btusb.sh";
+  };
+}