make jffs2 module provide o.rootfs, conditionally

it's enabled if config.rootfsType == "jffs2"

modules/base.nix

@@ -25,6 +25,10 @@ in {
       type = types.attrsOf type_service;
     };
     filesystem = mkOption { type = types.anything; };
+    rootfsType =  mkOption {
+      default = "squashfs";
+      type = types.str;
+    };
     kernel = {
       src = mkOption { type = types.package; } ;
       extraPatchPhase = mkOption {
@@ -107,7 +111,8 @@ in {
       };
     };
     boot.commandLine = [
-      "console=ttyS0,115200 panic=10 oops=panic init=/bin/init loglevel=8 rootfstype=squashfs"
+      "console=ttyS0,115200 panic=10 oops=panic init=/bin/init loglevel=8"
+      "rootfstype=${config.rootfsType}"
       "fw_devlink=off"
     ];
     users.root = {

modules/jffs2.nix

@@ -1,22 +1,24 @@
 {
   config
 , pkgs
+, lib
 , ...
 }:
 let
   inherit (pkgs) closureInfo;
+  inherit (lib) mkIf;
 in
 {
   imports = [
     ./initramfs.nix
   ];
-  config = {
+  config = mkIf (config.rootfsType == "jffs2") {
     kernel.config.JFFS2_FS = "y";
     boot.initramfs.enable = true;
     outputs = rec {
       systemConfiguration =
         pkgs.pkgsBuildBuild.systemconfig config.filesystem.contents;
-      jffs2fs =
+      rootfs =
         let
           inherit (pkgs.pkgsBuildBuild) runCommand mtdutils;
           endian = if pkgs.stdenv.isBigEndian
@@ -38,7 +40,7 @@ in
         pkgs.runCommand "jffs2boot" {} ''
           mkdir $out
           cd $out
-          ln -s ${o.jffs2fs} rootfs
+          ln -s ${o.rootfs} rootfs
           ln -s ${o.kernel} vmlinux
           ln -s ${o.manifest} manifest
           ln -s ${o.initramfs} initramfs

modules/outputs.nix

@@ -9,6 +9,9 @@ let
   inherit (pkgs) liminix callPackage writeText;
 in
 {
+  imports = [
+    ./squashfs.nix
+  ];
   options = {
     outputs = mkOption {
       type = types.attrsOf types.package;
@@ -17,7 +20,6 @@ in
   };
   config = {
     outputs = rec {
-      rootfs = liminix.builders.squashfs config.filesystem.contents;
       tftpd = pkgs.buildPackages.tufted;
       kernel = liminix.builders.kernel.override {
         inherit (config.kernel) config src extraPatchPhase;
@@ -38,7 +40,7 @@ in
       vmroot = pkgs.runCommand "qemu" {} ''
         mkdir $out
         cd $out
-        ln -s ${rootfs} rootfs
+        ln -s ${config.outputs.rootfs} rootfs
         ln -s ${kernel} vmlinux
         ln -s ${manifest} manifest
         ln -s ${kernel.headers} build

modules/squashfs.nix

@@ -0,0 +1,17 @@
+{
+  config
+, pkgs
+, lib
+, ...
+}:
+let
+  inherit (pkgs) liminix;
+  inherit (lib) mkIf;
+in
+{
+  config = mkIf (config.rootfsType == "squashfs") {
+    outputs = rec {
+      rootfs = liminix.builders.squashfs config.filesystem.contents;
+    };
+  };
+}

tests/jffs2/configuration.nix

@@ -4,4 +4,5 @@
     ../../vanilla-configuration.nix
     ../../modules/jffs2.nix
   ];
+  config.rootfsType = "jffs2";
 }