make kernel builder callPackage'able

default.nix

@@ -16,7 +16,9 @@ let
     ;
   };
   squashfs = (import ./make-image.nix) nixpkgs finalConfig;
-  kernel = (import ./make-kernel.nix)  nixpkgs finalConfig.kernel.config;
+  kernel = nixpkgs.pkgs.callPackage ./kernel {
+    inherit (finalConfig.kernel) config;
+  };
 in {
   outputs = {
     inherit squashfs kernel;

kernel/default.nix

@@ -1,12 +1,26 @@
-pkgs: config:
+{
+  callPackage
+, buildPackages
+, stdenvNoCC
+, fetchFromGitHub
+
+, config
+}:
 let
-  inherit (pkgs) callPackage buildPackages stdenvNoCC fetchFromGitHub;
   source = fetchFromGitHub {
     owner = "torvalds";
     repo = "linux";
     rev = "3d7cb6b04c3f3115719235cc6866b10326de34cd";  # v5.19
     hash = "sha256-OVsIRScAnrPleW1vbczRAj5L/SGGht2+GnvZJClMUu4=";
   };
+
+  # The kernel is huge and takes a long time just to
+  # download and unpack. This derivation creates
+  # a source tree in a suitable shape to build from -
+  # today it just patches some scripts but as we add
+  # support for boards/SoCs we expect the scope of
+  # "pre-treatment" to grow
+
   tree = stdenvNoCC.mkDerivation {
     name = "spindled-kernel-tree";
     src = source;
@@ -22,7 +36,7 @@ let
   };
 in
 {
-  vmlinux = callPackage ./make-vmlinux.nix {
+  vmlinux = callPackage ./vmlinux.nix {
     inherit tree;
     inherit config;
   };