From 422f3edab1136871f79b8579643fe0fb922fac3a Mon Sep 17 00:00:00 2001
From: Raito Bezarius <masterancpp@gmail.com>
Date: Sun, 18 Feb 2024 22:35:27 +0100
Subject: [PATCH] modules/zyxel-dual-image: init

This adds a simple boot blessing module, to be used, with the Zyxel NWA50AX.

There's a lot of elephant in the rooms: how do you upgrade kernel, etc.

Signed-off-by: Raito Bezarius <masterancpp@gmail.com>
---
 devices/zyxel-nwa50ax/default.nix    | 11 +++++
 modules/zyxel-dual-image/default.nix | 60 ++++++++++++++++++++++++++++
 modules/zyxel-dual-image/service.nix | 33 +++++++++++++++
 pkgs/zyxel-bootconfig/default.nix    |  3 ++
 4 files changed, 107 insertions(+)
 create mode 100644 modules/zyxel-dual-image/default.nix
 create mode 100644 modules/zyxel-dual-image/service.nix

diff --git a/devices/zyxel-nwa50ax/default.nix b/devices/zyxel-nwa50ax/default.nix
index 7c5e09b..a6c77c6 100644
--- a/devices/zyxel-nwa50ax/default.nix
+++ b/devices/zyxel-nwa50ax/default.nix
@@ -94,6 +94,7 @@
         ../../modules/arch/mipsel.nix
         ../../modules/outputs/tftpboot.nix
         ../../modules/outputs/zyxel-nwa-fit.nix
+        ../../modules/zyxel-dual-image
       ];
 
       filesystem = dir {
@@ -168,6 +169,7 @@
             };
           };
       };
+
       boot = {
         # Critical because NWA50AX will extend your cmdline with the image number booted.
         # and some bootloader version.
@@ -182,6 +184,15 @@
         };
       };
 
+      # Dual image management service in userspace.
+      services.zyxel-dual-image = config.boot.zyxel-dual-image.build {
+        ensureActiveImage = "primary";
+        # TODO: use mtd names rather…
+        primaryMtdPartition = "/dev/mtd3";
+        secondaryMtdPartition = "/dev/mtd6";
+        bootConfigurationMtdPartition = "/dev/mtd10";
+      };
+
       #  DEVICE_VENDOR := ZyXEL
       #  KERNEL_SIZE := 8192k
       #  DEVICE_PACKAGES := kmod-mt7915-firmware zyxel-bootconfig
diff --git a/modules/zyxel-dual-image/default.nix b/modules/zyxel-dual-image/default.nix
new file mode 100644
index 0000000..91ed48e
--- /dev/null
+++ b/modules/zyxel-dual-image/default.nix
@@ -0,0 +1,60 @@
+## Boot blessing via Zyxel
+## =======================
+## Boot blessing is the process to bless a particular boot configuration
+## It is commonly encountered in devices with redundant partitions
+## for automatic recovery of broken upgrades.
+## This is also known as A/B schemas, where A represents the primary partition
+## and B the secondary partition used for recovery.
+## To use boot blessing on Liminix, you need to have the support of
+## your bootloader to help you boot on the secondary partition in case of
+## failure on the primary partition. The exact details are specifics to your device.
+## See the Zyxel NWA50AX for an example.
+## TODO: generalize this module.
+{ config, lib, pkgs, ... }:
+let
+  inherit (lib) mkOption types;
+  inherit (pkgs) liminix;
+in
+{
+  options.boot.zyxel-dual-image = mkOption {
+    type = liminix.lib.types.serviceDefn;
+  };
+
+  config.boot.zyxel-dual-image = liminix.callService ./service.nix {
+    ensureActiveImage = mkOption {
+      type = types.enum [ "primary" "secondary" ];
+      default = "primary";
+      description = ''At boot, ensure that the active image is the one specified.
+
+        If you are already on a broken image, you need to manually boot
+        into the right image via `atgo <image index>` in U-Boot.
+      '';
+    };
+
+    kernelCommandLineSource = mkOption {
+      type = types.enum [ "/proc/cmdline" "/proc/device-tree/chosen/bootargs" ];
+      default = "/proc/device-tree/chosen/bootargs";
+      description = ''Kernel command line arguments source file.
+        On MIPS, Liminix embeds the kernel command line in /proc/device-tree/chosen/bootargs-override.
+
+        In this instance, it does not get concatenated with `/proc/cmdline`.
+        Therefore you may prefer to source it from another place, like `/proc/device-tree/chosen/bootargs`.
+      '';
+    };
+
+    primaryMtdPartition = mkOption {
+      type = types.str;
+      description = "Primary MTD partition device node, i.e. for image 0.";
+    };
+
+    secondaryMtdPartition = mkOption {
+      type = types.str;
+      description = "Secondary MTD partition device node, i.e. for image 1.";
+    };
+
+    bootConfigurationMtdPartition = mkOption {
+      type = types.str;
+      description = "Boot configuration MTD partition device node.";
+    };
+  };
+}
diff --git a/modules/zyxel-dual-image/service.nix b/modules/zyxel-dual-image/service.nix
new file mode 100644
index 0000000..3edd642
--- /dev/null
+++ b/modules/zyxel-dual-image/service.nix
@@ -0,0 +1,33 @@
+{
+  liminix
+, lib
+, zyxel-bootconfig
+}:
+{ ensureActiveImage, primaryMtdPartition, secondaryMtdPartition, bootConfigurationMtdPartition, kernelCommandLineSource }:
+let
+  inherit (liminix.services) oneshot;
+  activeImageIndex = if ensureActiveImage == "primary" then 0 else 1;
+in oneshot {
+  name = "zyxel-boot-configure";
+  up = ''
+    set -- $(cat /proc/device-tree/chosen/bootargs)
+    for x in "$@"; do
+        case "$x" in
+            bootImage=*)
+            BOOT_IMAGE="''${x#bootImage=}"
+            echo "Current boot image is $BOOT_IMAGE."
+            ;;
+        esac
+    done
+
+    if test -z "$BOOT_IMAGE"; then
+      echo "No valid image was provided in the kernel command line."
+      exit 1
+    else
+      ${lib.getExe zyxel-bootconfig} ${bootConfigurationMtdPartition} set-image-status "$BOOT_IMAGE" valid
+      ${lib.getExe zyxel-bootconfig} ${bootConfigurationMtdPartition} set-active-image ${toString activeImageIndex}
+
+      echo "Active image is now ${ensureActiveImage}"
+    fi
+  '';
+}
diff --git a/pkgs/zyxel-bootconfig/default.nix b/pkgs/zyxel-bootconfig/default.nix
index ead47e6..ce148ae 100644
--- a/pkgs/zyxel-bootconfig/default.nix
+++ b/pkgs/zyxel-bootconfig/default.nix
@@ -10,4 +10,7 @@ stdenv.mkDerivation {
     mkdir -p $out/bin
     install -Dm644 zyxel-bootconfig $out/bin/zyxel-bootconfig
   '';
+  meta = {
+    mainProgram = "zyxel-bootconfig";
+  };
 }