add per-device overlay

presently this is used to reference the appropriate kernel and (if
needed) openwrt source trees, but I would not be surprised if we find
other uses

default.nix

@@ -5,7 +5,7 @@
 
 let
   overlay = import ./overlay.nix;
-  nixpkgs = import <nixpkgs> ( device.system // {overlays = [overlay]; });
+  nixpkgs = import <nixpkgs> (device.system // {overlays = [overlay device.overlay]; });
   inherit (nixpkgs.pkgs) callPackage writeText liminix;
   inherit (nixpkgs.lib) concatStringsSep;
   config = (import ./merge-modules.nix) [
@@ -56,16 +56,18 @@ let
           bootm 0x${toHexString uimageStart}
         '';
 
-    directory = nixpkgs.pkgs.runCommand "liminix" {} ''
+    directory = nixpkgs.pkgs.runCommand "liminix" {} (''
       mkdir $out
       cd $out
       ln -s ${squashfs} squashfs
       ln -s ${kernel.vmlinux} vmlinux
       ln -s ${manifest} manifest
+    '' +
+    (if device ? boot then ''
       ln -s ${uimage} uimage
       ${if phram then "ln -s ${boot-scr} boot.scr" else ""}
       ln -s ${boot-scr} flash.scr
-    '';
+    '' else ""));
     # this exists so that you can run "nix-store -q --tree" on it and find
     # out what's in the image, which is nice if it's unexpectedly huge
     manifest = writeText "manifest.json" (builtins.toJSON config.filesystem.contents);

devices/gl-ar750/default.nix

@@ -20,6 +20,34 @@
       };
     };
   };
+
+  # We need to be able to import default.nix before we import nixpkgs
+  # because it has the system config to tell nixpkgs what arch to build for.
+  # But we also need some way to do things like fetchFromGitHub in the
+  # per-device config and we can only do that once we have a reference to
+  # pkgs
+
+  overlay = final: prev:
+    let inherit (final) fetchFromGitHub;
+    in {
+      sources = {
+        openwrt = fetchFromGitHub {
+          name = "openwrt-source";
+          repo = "openwrt";
+          owner = "openwrt";
+          rev = "a5265497a4f6da158e95d6a450cb2cb6dc085cab";
+          hash = "sha256-YYi4gkpLjbOK7bM2MGQjAyEBuXJ9JNXoz/JEmYf8xE8=";
+        };
+        kernel =  fetchFromGitHub {
+          name = "kernel-source";
+          owner = "torvalds";
+          repo = "linux";
+          rev = "3d7cb6b04c3f3115719235cc6866b10326de34cd";  # v5.19
+          hash = "sha256-OVsIRScAnrPleW1vbczRAj5L/SGGht2+GnvZJClMUu4=";
+        };
+      };
+    };
+
   kernel = rec {
     checkedConfig = {
       "MIPS_ELF_APPENDED_DTB" = "y";
@@ -42,7 +70,6 @@
       CONSOLE_LOGLEVEL_DEFAULT = "8";
       CONSOLE_LOGLEVEL_QUIET = "4";
 
-
       # "empty" initramfs source should create an initial
       # filesystem that has a /dev/console node and not much
       # else.  Note that pid 1 is started *before* the root

devices/qemu/default.nix

@@ -12,6 +12,21 @@
       };
     };
   };
+
+  overlay = final: prev:
+    let inherit (final) fetchFromGitHub;
+    in {
+      sources = {
+        kernel =  fetchFromGitHub {
+          name = "kernel-source";
+          owner = "torvalds";
+          repo = "linux";
+          rev = "3d7cb6b04c3f3115719235cc6866b10326de34cd";  # v5.19
+          hash = "sha256-OVsIRScAnrPleW1vbczRAj5L/SGGht2+GnvZJClMUu4=";
+        };
+      };
+    };
+
   kernel = {
     config = {
       SYSVIPC= "y";

kernel/default.nix

@@ -6,15 +6,9 @@
 
 , config
 , checkedConfig
+, sources
 }:
 let
-  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 -
@@ -24,7 +18,7 @@ let
 
   tree = stdenvNoCC.mkDerivation {
     name = "spindled-kernel-tree";
-    src = source;
+    src = sources.kernel;
     phases = [ "unpackPhase" "patchPhase" "patchScripts" "installPhase" ];
     patches = [ ./random.patch ];
     patchScripts = ''
@@ -36,15 +30,6 @@ let
     '';
   };
 
-  openwrtSource = fetchFromGitHub {
-    name = "openwrt-source-tree";
-    repo = "openwrt";
-    owner = "openwrt";
-    rev = "a5265497a4f6da158e95d6a450cb2cb6dc085cab";
-    hash = "sha256-YYi4gkpLjbOK7bM2MGQjAyEBuXJ9JNXoz/JEmYf8xE8=";
-  };
-
-
 in rec {
   vmlinux = callPackage ./vmlinux.nix {
     inherit tree config checkedConfig;
@@ -53,7 +38,7 @@ in rec {
   uimage = callPackage ./uimage.nix { };
 
   dtb = callPackage ./dtb.nix {
-    openwrt = openwrtSource;
+    openwrt = sources.openwrt;
     kernel = tree;
   };
 }

tests/kernel/run.sh

@@ -1,5 +1,5 @@
 set -e
-NIXPKGS_ALLOW_UNSUPPORTED_SYSTEM=1 nix-build '<liminix>' -I liminix-config=../smoke/configuration.nix --arg device "import <liminix/devices/$DEVICE.nix>" -A outputs.kernel.vmlinux -o vmlinux $*
+NIXPKGS_ALLOW_UNSUPPORTED_SYSTEM=1 nix-build '<liminix>' -I liminix-config=../smoke/configuration.nix --arg device "import <liminix/devices/$DEVICE>" -A outputs.kernel.vmlinux -o vmlinux $*
 
 TESTS=$(cat <<"EOF"
 

tests/module/run.sh

@@ -1,2 +1,2 @@
 set -e
-NIXPKGS_ALLOW_UNSUPPORTED_SYSTEM=1 nix-build --arg device "import <liminix/devices/qemu.nix>" test.nix
+NIXPKGS_ALLOW_UNSUPPORTED_SYSTEM=1 nix-build --arg device "import <liminix/devices/qemu>" test.nix

tests/pppoe/run.sh

@@ -14,7 +14,7 @@ fatal(){
 }
 trap fatal ERR
 
-NIXPKGS_ALLOW_UNSUPPORTED_SYSTEM=1 nix-build '<liminix>' -I liminix-config=./configuration.nix --arg device "import <liminix/devices/qemu.nix>" -A outputs.default $*
+NIXPKGS_ALLOW_UNSUPPORTED_SYSTEM=1 nix-build '<liminix>' -I liminix-config=./configuration.nix --arg device "import <liminix/devices/qemu>" -A outputs.default $*
 
 if ! ( echo "cont" | socat - unix-connect:../support/ppp-server/qemu-monitor); then
     echo "need pppoe server running"

tests/smoke/run.sh

@@ -1,5 +1,5 @@
 set -e
-NIXPKGS_ALLOW_UNSUPPORTED_SYSTEM=1 nix-build '<liminix>' -I liminix-config=./configuration.nix --arg device "import <liminix/devices/$DEVICE.nix>" -A outputs.squashfs -o smoke.img $*
+NIXPKGS_ALLOW_UNSUPPORTED_SYSTEM=1 nix-build '<liminix>' -I liminix-config=./configuration.nix --arg device "import <liminix/devices/$DEVICE>" -A outputs.squashfs -o smoke.img $*
 
 TESTS=$(cat <<"EOF"
 test -n "${TMPDIR}"

tests/wlan/run.sh

@@ -14,7 +14,7 @@ fatal(){
 }
 trap fatal ERR
 
-NIXPKGS_ALLOW_UNSUPPORTED_SYSTEM=1 nix-build '<liminix>' -I liminix-config=./configuration.nix --arg device "import <liminix/devices/qemu.nix>" -A outputs.default $*
+NIXPKGS_ALLOW_UNSUPPORTED_SYSTEM=1 nix-build '<liminix>' -I liminix-config=./configuration.nix --arg device "import <liminix/devices/qemu>" -A outputs.default $*