convert devices from overlay to module

this makes it possible for devices to stash things in
`config` (e.g. pathname to DTS) that can later be overwritten
(even by the end user)

default.nix

@@ -8,14 +8,14 @@
 let
   overlay = import ./overlay.nix;
   pkgs = import nixpkgs (device.system // {
-    overlays = [overlay device.overlay];
+    overlays = [overlay];
     config = {allowUnsupportedSystem = true; };
   });
   inherit (pkgs) callPackage writeText liminix fetchFromGitHub;
   inherit (pkgs.lib) concatStringsSep;
   config = (import ./merge-modules.nix) [
     ./modules/base.nix
-    ({ lib, ... } : { config = { inherit (device) kernel; }; })
+    device.module
     liminix-config
     ./modules/s6
     ./modules/users.nix
@@ -33,11 +33,11 @@ let
 
   outputs = rec {
     inherit squashfs;
-    kernel = pkgs.kernel.override {
+    kernel = liminix.builders.kernel.override {
-      inherit (config.kernel) config;
+      inherit (config.kernel) config src extraPatchPhase;
     };
     dtb =  (callPackage ./kernel/dtb.nix {}) {
-      dts = config.kernel.dts { inherit openwrt; };
+      dts = config.kernel.dts;
       includes = [
         "${openwrt}/target/linux/ath79/dts"
         "${kernel.headers}/include"
@@ -91,7 +91,7 @@ let
     tftpd = pkgs.buildPackages.tufted;
   };
 in {
-  outputs = outputs // { default = outputs.${device.outputs.default}; };
+  outputs = outputs // { default = outputs.${config.device.defaultOutput}; };
 
   # this is just here as a convenience, so that we can get a
   # cross-compiling nix-shell for any package we're customizing

devices/gl-ar750/default.nix

@@ -24,15 +24,9 @@
     };
   };
 
-  # We need to be able to import default.nix before we import nixpkgs
+  module = {pkgs, ... }:
-  # 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
-      openwrt = final.fetchFromGitHub {
+      openwrt = pkgs.pkgsBuildBuild.fetchFromGitHub {
         name = "openwrt-source";
         repo = "openwrt";
         owner = "openwrt";
@@ -40,8 +34,14 @@
         hash = "sha256-YYi4gkpLjbOK7bM2MGQjAyEBuXJ9JNXoz/JEmYf8xE8=";
       };
     in {
-      kernel = prev.kernel.override {
+      device.defaultOutput = "directory";
-        src = final.fetchurl {
+      device.boot = {
+        loadAddress = "0x80060000";
+        entryPoint  = "0x80060000";
+      };
+
+      kernel = {
+        src = pkgs.pkgsBuildBuild.fetchurl {
           name = "linux.tar.gz";
           url = "https://cdn.kernel.org/pub/linux/kernel/v5.x/linux-5.15.71.tar.gz";
           hash = "sha256-yhO2cXIeIgUxkSZf/4aAsF11uxyh+UUZu6D1h92vCD8=";
@@ -59,10 +59,7 @@
           patches ${openwrt}/target/linux/generic/hack-5.15/*.patch
           patches ${openwrt}/target/linux/ath79/patches-5.15/*.patch
         '';
-      };
+        dts = "${openwrt}/target/linux/ath79/dts/qca9531_glinet_gl-ar750.dts";
-    };
-  kernel = rec {
-    dts = { openwrt,... }:"${openwrt}/target/linux/ath79/dts/qca9531_glinet_gl-ar750.dts";
         config = {
           MIPS_ELF_APPENDED_DTB = "y";
           OF = "y";
@@ -122,9 +119,5 @@
           "SQUASHFS_XZ" = "y";
         };
       };
-  outputs.default = "directory";
-  boot = {
-    loadAddress = "0x80060000";
-    entryPoint  = "0x80060000";
     };
 }

devices/gl-mt300a/default.nix

@@ -11,15 +11,9 @@
     };
   };
 
-  # We need to be able to import default.nix before we import nixpkgs
+  module = { pkgs, ...}:
-  # 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
-      openwrt = final.fetchFromGitHub {
+      openwrt = pkgs.fetchFromGitHub {
         name = "openwrt-source";
         repo = "openwrt";
         owner = "openwrt";
@@ -27,8 +21,16 @@
         hash = "sha256-YYi4gkpLjbOK7bM2MGQjAyEBuXJ9JNXoz/JEmYf8xE8=";
       };
     in {
-      kernel = prev.kernel.override {
+      device = {
-        src = final.fetchurl {
+        defaultOutput = "directory";
+        boot = {
+          loadAddress = "0x80000000";
+          entryPoint  = "0x80000000";
+        };
+      };
+
+      kernel = {
+        src = pkgs.fetchurl {
           name = "linux.tar.gz";
           url = "https://cdn.kernel.org/pub/linux/kernel/v5.x/linux-5.15.71.tar.gz";
           hash = "sha256-yhO2cXIeIgUxkSZf/4aAsF11uxyh+UUZu6D1h92vCD8=";
@@ -46,10 +48,7 @@
           patches ${openwrt}/target/linux/generic/hack-5.15/*.patch
           patches ${openwrt}/target/linux/ramips/patches-5.15/*.patch
         '';
-      };
+        dts = "${openwrt}/target/linux/ramips/dts/mt7620a_glinet_gl-mt300a.dts";
-    };
-  kernel = rec {
-    dts = { openwrt,... } : "${openwrt}/target/linux/ramips/dts/mt7620a_glinet_gl-mt300a.dts";
         config = {
           MIPS_ELF_APPENDED_DTB = "y";
           OF = "y";
@@ -106,9 +105,5 @@
           "SQUASHFS_XZ" = "y";
         };
       };
-  outputs.default = "directory";
-  boot = {
-    loadAddress = "0x80000000";
-    entryPoint  = "0x80000000";
     };
 }

devices/gl-mt300n-v2/default.nix

@@ -11,15 +11,9 @@
     };
   };
 
-  # We need to be able to import default.nix before we import nixpkgs
+  module = { pkgs, ...}:
-  # 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
-      openwrt = final.fetchFromGitHub {
+      openwrt = pkgs.fetchFromGitHub {
         name = "openwrt-source";
         repo = "openwrt";
         owner = "openwrt";
@@ -27,8 +21,16 @@
         hash = "sha256-YYi4gkpLjbOK7bM2MGQjAyEBuXJ9JNXoz/JEmYf8xE8=";
       };
     in {
-      kernel = prev.kernel.override {
+      device = {
-        src = final.fetchurl {
+        defaultOutput = "directory";
+        boot = {
+          loadAddress = "0x80000000";
+          entryPoint  = "0x80000000";
+        };
+      };
+
+      kernel = {
+        src = pkgs.fetchurl {
           name = "linux.tar.gz";
           url = "https://cdn.kernel.org/pub/linux/kernel/v5.x/linux-5.15.71.tar.gz";
           hash = "sha256-yhO2cXIeIgUxkSZf/4aAsF11uxyh+UUZu6D1h92vCD8=";
@@ -46,10 +48,7 @@
           patches ${openwrt}/target/linux/generic/hack-5.15/*.patch
           patches ${openwrt}/target/linux/ramips/patches-5.15/*.patch
         '';
-      };
+        dts = "${openwrt}/target/linux/ramips/dts/mt7628an_glinet_gl-mt300n-v2.dts";
-    };
-  kernel = rec {
-    dts = { openwrt,... } : "${openwrt}/target/linux/ramips/dts/mt7628an_glinet_gl-mt300n-v2.dts";
         config = {
           MIPS_ELF_APPENDED_DTB = "y";
           OF = "y";
@@ -117,9 +116,5 @@
           "SQUASHFS_XZ" = "y";
         };
       };
-  outputs.default = "directory";
-  boot = {
-    loadAddress = "0x80000000";
-    entryPoint  = "0x80000000";
     };
 }

devices/qemu/default.nix

@@ -13,22 +13,13 @@
     };
   };
 
-  overlay = final: prev:
+  module = {pkgs, ... }: {
-    let inherit (final) stdenvNoCC fetchFromGitHub;
+    kernel = {
-    in {
+      src = pkgs.pkgsBuildBuild.fetchurl {
-      kernel = prev.kernel.override {
-        # using fetchurl not fetchzip because it doesn't unpack, and
-        # copying 6GB of data from one store location to another
-        # takes an absolute bloody age
-        src = final.fetchurl {
         name = "linux.tar.gz";
         url = "https://cdn.kernel.org/pub/linux/kernel/v5.x/linux-5.19.16.tar.gz";
         hash = "sha256-m4NeoEsCEK0HSIKTZ6zYTgk1fD3W0PSOMXN6fyHpkP8=";
       };
-      };
-    };
-
-  kernel = {
       config = {
         MIPS_MALTA= "y";
         CPU_LITTLE_ENDIAN= "n";
@@ -50,5 +41,6 @@
         SERIAL_8250_CONSOLE= "y";
       };
     };
-  outputs.default = "directory";
+    device.defaultOutput = "directory";
+  };
 }

modules/base.nix

@@ -24,7 +24,12 @@ in {
     };
     filesystem = mkOption { type = types.anything; };
     kernel = {
-      dts = mkOption { type = types.functionTo types.string; };
+      src = mkOption { type = types.package; } ;
+      extraPatchPhase = mkOption {
+        default = "true";
+        type = types.lines;
+      } ;
+      dts = mkOption { type = types.string; };
       config = mkOption {
         # mostly the values are y n or m, but sometimes
         # other strings are also used
@@ -40,6 +45,12 @@ in {
     users =  mkOption {
       type = types.attrsOf types.anything;
     };
+    device = {
+      defaultOutput = mkOption {
+        type = types.nonEmptyStr;
+      };
+      boot = mkOption { type = types.any; };
+    };
   };
   config = {
     defaultProfile.packages = with pkgs;

overlay.nix

@@ -6,14 +6,13 @@ final: prev: {
     networking =  final.callPackage ./pkgs/liminix-tools/networking {};
     builders =  {
       squashfs = final.callPackage ./pkgs/liminix-tools/builders/squashfs.nix {};
+      kernel = final.callPackage ./pkgs/kernel {};
     };
   };
   writeAshScript = final.callPackage ./pkgs/write-ash-script {};
   s6-init-bin =  final.callPackage ./pkgs/s6-init-bin {};
   s6-rc-database = final.callPackage ./pkgs/s6-rc-database {};
 
-  kernel = final.callPackage ./pkgs/kernel {};
-
   dnsmasq =
     let d =  prev.dnsmasq.overrideAttrs(o: {
           preBuild =  ''

pkgs/kernel/default.nix

@@ -6,7 +6,7 @@
 
  , config
  , src
- , extraPatchPhase ? "true"
+ , extraPatchPhase ? "echo"
 } :
 let writeConfig = name : config: writeText name
         (builtins.concatStringsSep