rt3200 needs pmsg-size set in its dts for persistent logging

for the record, u-boot doesn't like having /boot/fit -> ../nix/store/..../fit
symlinks so we don't use symlinks inside /boot either

devices/belkin-rt3200/default.nix

@@ -86,16 +86,25 @@
         Name:        liminix
         Character device major/minor: 250:8
         root@OpenWrt:~# ubiupdatevol /dev/ubi0_7 /tmp/rootfs
-        root@OpenWrt:~# fw_setenv orig_boot_production $(fw_printenv boot_production | sed -E 's/.+?=//')
+
+    To make the new system bootable we also need to change some U-Boot variables.
+    ``boot_production`` needs to mount the filesystem and boot the FIT image
+    found there, and :code:`bootcmd` needs to be told _not_ to boot the rescue
+    image if there are records in pstore, because that interferes with
+    ``config.log.persistent``
+
+        root@OpenWrt:~# fw_setenv orig_boot_production $(fw_printenv -n boot_production)
+        root@OpenWrt:~# fw_setenv orig_bootcmd $(fw_printenv -n bootcmd)
         root@OpenWrt:~# fw_setenv boot_production 'led $bootled_pwr on ; ubifsmount ubi0:liminix && ubifsload ''${loadaddr} boot/fit && bootm ''${loadaddr}'
+        root@OpenWrt:~# fw_setenv bootcmd 'run boot_ubi'
 
-
-    For subsequent Liminix reinstalls, you don't need to repeat the
-    "Preparation" step and in fact should seek to avoid it if
-    possible. Updating volumes with :command:`ubiupdatevol` will
-    preserve the erase counters used for write levelling, so is
-    preferred over any kind of "factory" wipe which will reset them.
-     '';
+    For subsequent Liminix reinstalls, just run the
+    :command:`ubiupdatevol` command again. You don't need to repeat
+    the "Preparation" step and in fact should seek to avoid it if
+    possible, as it will reset the erase counters used for write
+    levelling.  Using UBI-aware tools is therefore preferred over any
+    kind of "factory" wipe which will reset them.
+    '';
 
   system = {
     crossSystem = {
@@ -104,7 +113,8 @@
   };
 
   module = {pkgs, config, lib, lim, ... }:
-    let firmware = pkgs.stdenv.mkDerivation {
+    let inherit (lib) mkIf;
+        firmware = pkgs.stdenv.mkDerivation {
           name = "wlan-firmware";
           phases = ["installPhase"];
           installPhase = ''
@@ -259,6 +269,9 @@
             "${openwrt.src}/target/linux/mediatek/dts"
             "${config.system.outputs.kernel.modulesupport}/arch/arm64/boot/dts/mediatek/"
           ];
+          includes = mkIf config.logging.persistent.enable [
+            ./pstore-pmsg.dtsi
+          ];
         };
 
         # - 0x000000000000-0x000008000000 : "spi-nand0"

devices/belkin-rt3200/pstore-pmsg.dtsi

@@ -0,0 +1,8 @@
+/ {
+	reserved-memory {
+		/* make sure address matches upstream  */
+		ramoops@42ff0000 {
+			pmsg-size = <0x10000>;
+		};
+	};
+};

modules/outputs/ubimage.nix

@@ -7,10 +7,12 @@
 let
   inherit (lib) mkIf mkOption types;
   cfg = config.boot.tftp;
-  instructions = pkgs.writeText "env.scr" ''
+  instructions = pkgs.writeText "flash.scr" ''
     setenv serverip ${cfg.serverip}
     setenv ipaddr ${cfg.ipaddr}
     setenv loadaddr ${lib.toHexString cfg.loadAddress}
+    tftpboot $loadaddr result/rootfs
+    ubi write $loadaddr liminix $filesize
 '';
 in {
   options.system.outputs = {
@@ -63,18 +65,20 @@ Now we can make our new root volume
 
     uboot> ubi create liminix -
 
-3) transfer the root filesystem from the build system and write it
-to the new volume. Paste the environment variable settings from
-:file:`result/env.scr` into U-Boot, then run
+3) transfer the root filesystem from the build system and write it to
+the new volume. Paste the contents of :file:`result/flash.scr` one line at a time
+into U-Boot:
 
 .. code-block:: console
 
-    uboot> tftpboot ''${loadaddr} result/rootfs
-    uboot> ubi write ''${loadaddr} liminix $filesize
+    uboot> setenv serverip 10.0.0.1
+    uboot> setenv ipaddr 10.0.0.8
+    uboot> setenv loadaddr 4007FF28
+    uboot> tftpboot $loadaddr result/rootfs
+    uboot> ubi write $loadaddr liminix $filesize
 
 Now we have the root filesystem installed on the device. You
-can even mount it and poke around using ``ubifsmount ubi0:liminix;
-ubifsls  /``
+can even mount it and poke around using :command:`ubifsmount ubi0:liminix; ubifsls  /`
 
 4) optional: before you configure the device to boot into Liminix
 automatically, you can try booting it by hand to see if it works:
@@ -89,20 +93,11 @@ Once you've done this and you're happy with it, reset the device to
 return to U-Boot.
 
 5) Instructions for configuring autoboot are likely to be very
-device-dependent. On the Linksys E8450/Belkin RT3200, the environment
-variable `boot_production` governs what happens on a normal boot, so
-you could do
-
-.. code-block:: console
-
-    uboot> setenv orig_boot_production $boot_production
-    uboot> setenv boot_production 'led $bootled_pwr on ; ubifsmount ubi0:liminix && ubifsload ''${loadaddr} boot/fit && bootm ''${loadaddr}'
-    uboot> saveenv
-    uboot> reset
-
-On other devices, some detective work may be needed. Try running
-`printenv` and look for likely commands, try looking at the existing
-boot process, maybe even try looking for documentation for that device.
+device-dependent and you should consult the Liminix documentation for
+your device.  (If you're bringing up a new device, some detective work
+may be needed. Try running `printenv` and trace through the flow of
+execution from (probably) :command:`$bootcmd` and look for a suitable
+variable to change)
 
 6) Now you can reboot the device into Liminix
 
@@ -120,6 +115,6 @@ boot process, maybe even try looking for documentation for that device.
       mkdir $out
       cd $out
       ln -s ${o.rootfs} rootfs
-      ln -s ${instructions} env.scr
+      ln -s ${instructions} flash.scr
    '';
 }

modules/outputs/updater/default.nix

@@ -27,7 +27,8 @@ in
 
   config.system.outputs.updater =
     runCommand "buildUpdater" { } ''
-      mkdir -p $out/bin
+      mkdir -p $out/bin $out/etc
+      cp ${o.kernel.config} $out/etc/kconfig
       substitute ${./update.sh} $out/bin/update.sh \
          --subst-var-by toplevel ${o.systemConfiguration} \
          --subst-var-by min_copy_closure ${min-copy-closure}

pkgs/kernel/default.nix

@@ -45,7 +45,7 @@ stdenv.mkDerivation rec {
 
   dontStrip = true;
   dontPatchELF = true;
-  outputs = ["out" "headers" "modulesupport"] ++ targetNames;
+  outputs = ["out" "headers" "modulesupport" "config"] ++ targetNames;
   phases = [
     "unpackPhase"
     "butcherPkgconfig"
@@ -114,5 +114,6 @@ stdenv.mkDerivation rec {
     mkdir -p $modulesupport
     make modules
     cp -a . $modulesupport
+    cp .config $config
   '';
 }

pkgs/systemconfig/default.nix

@@ -99,8 +99,10 @@ in attrset:
       cp -v -fP \$src/bin/* \$src/etc/* \$dest
       ${if attrset ? boot then ''
         (cd \$dest
-         if test -e boot ; then rm boot ; fi
-         ln -sf ${lib.strings.removePrefix "/" attrset.boot.target} ./boot
+         test -d boot || mkdir boot
+         cd boot
+         cp ../${lib.strings.removePrefix "/" attrset.boot.target}/* .
+         sync; sync
         )
       '' else ""}
       EOF