Add freefall: hard drive protection on HP/Dell laptops

pkgs/os-specific/linux/freefall/default.nix

@@ -0,0 +1,42 @@
+{ stdenv, fetchurl }:
+
+stdenv.mkDerivation rec {
+  version = "3.18.3";
+  name = "freefall-${version}";
+
+  src = fetchurl {
+    url = "mirror://kernel/linux/kernel/v3.x/linux-${version}.tar.xz";
+    sha256 = "0ma2x68975xsi9kb15p0615nx9sm5ppb309kfdz7fgx9pg84q0hf";
+  };
+
+  buildPhase = ''
+    cd Documentation/laptops
+
+    # Default time-out is a little low, probably because the AC/lid status
+    # functions were never implemented. Because no-one still uses HDDs, right?
+    substituteInPlace freefall.c --replace "alarm(2)" "alarm(5)"
+
+    cc -o freefall freefall.c
+  '';
+
+  installPhase = ''
+    mkdir -p $out/bin
+    install freefall $out/bin
+  '';
+
+  meta = with stdenv.lib; {
+    description = "Free-fall protection for spinning HP/Dell laptop hard drives";
+    longDescription = ''
+      ATA/ATAPI-7 specifies the IDLE IMMEDIATE command with unload feature.
+      Issuing this command should cause the drive to switch to idle mode and
+      unload disk heads. This feature is being used in modern laptops in
+      conjunction with accelerometers and appropriate software to implement
+      a shock protection facility. The idea is to stop all I/O operations on
+      the internal hard drive and park its heads on the ramp when critical
+      situations are anticipated. This has no effect on SSD devices!
+    '';
+    license = with licenses; gpl2;
+    platforms = with platforms; linux;
+    maintainers = with maintainers; [ nckx ];
+  };
+}

pkgs/top-level/all-packages.nix

@@ -8415,6 +8415,8 @@ let
 
   firejail = callPackage ../os-specific/linux/firejail {};
 
+  freefall = callPackage ../os-specific/linux/freefall { };
+
   fuse = callPackage ../os-specific/linux/fuse { };
 
   fxload = callPackage ../os-specific/linux/fxload { };