feat: add Nix and NixOS assets

Author: tomeon

.gitignore

@@ -1,3 +1,14 @@
 node_modules
 db/*
 *.log
+
+# VM disk images
+*.qcow2
+
+# Nix build results
+result
+result-*
+repl-result-*
+
+# NixOS test driver REPL history
+.nixos-test-history

app.nix

@@ -0,0 +1,36 @@
+{
+  lib,
+  config,
+  dream2nix,
+  pkgs,
+  ...
+} @ args: let
+  packageJSON = lib.importJSON ./package.json;
+in {
+  imports = [
+    dream2nix.modules.dream2nix.nodejs-package-json-v3
+    dream2nix.modules.dream2nix.nodejs-granular-v3
+  ];
+
+  inherit (packageJSON) name version;
+
+  # Take advantage of a shell injection vector in dream2nix in order to apply a
+  # workaround for an issue with `npm i` converting dependencies specified with
+  # `git+https://` or `github:` to `git+ssh://`.
+  # See:
+  #   - https://github.com/npm/cli/issues/2610
+  #   - https://github.com/npm/cli/issues/2631
+  nodejs-package-json.npmArgs = lib.mkAfter [
+    "--package-lock-only' ; ${lib.getExe pkgs.gnused} -i -e 's|git+ssh://|git+https://|g' ./package-lock.json #"
+  ];
+
+  mkDerivation = {
+    src = lib.cleanSource ./.;
+    doCheck = false;
+    meta = {
+      # XXX broken somehow? `lib.licenses.gpl3` works...
+      #license = lib.licenses.cc-by-nc-40;
+      homepage = "https://github.com/LowPowerLab/RaspberryPi-Gateway";
+    };
+  };
+}

device-trees-overlay-dtmerge.nixh:device-tree-apply-overlays-dtmerge/g.nix

@@ -0,0 +1,84 @@
+# Modification of nixpkgs deviceTree.applyOverlays to resolve https://github.com/NixOS/nixpkgs/issues/125354.
+#
+# Derived from https://github.com/NixOS/nixpkgs/blob/916ca8f2b0c208def051f8ea9760c534a40309db/pkgs/os-specific/linux/device-tree/default.nix.
+#
+# This replaces the default device tree overlay application process
+# to use `dtmerge` from `libraspberrypi`.  The default overlay
+# application process can be problematic on Raspberry Pis due to
+# (among other things) issues like this:
+#
+#   https://github.com/raspberrypi/firmware/issues/1718
+#
+# and `fdtget`-based compatibility checks, which yield false
+# negatives (overlay is compatible, but the check says it is not):
+#
+#   $ dtbCompat="$(fdtget -t s ./boot/bcm2710-rpi-3-b-plus.dtb / compatible | tee /dev/stderr)"
+#   raspberrypi,3-model-b-plus brcm,bcm2837
+#   $ overlayCompat="$(fdtget -t s ./boot/overlays/disable-bt.dtbo / compatible | tee /dev/stderr)"
+#   brcm,bcm2835
+#   $ [[ "$dtbCompat" =~ "$overlayCompat" ]] ; echo "$?"
+#   1
+#
+# The upstream/default merging logic is here:
+#
+# https://github.com/NixOS/nixpkgs/blob/c999f2e369508fca13646ca5a0fb926b3ce0063e/pkgs/os-specific/linux/device-tree/default.nix#L27-L65
+#
+# The `nixos-hardware` override is here:
+#
+# https://github.com/NixOS/nixos-hardware/blob/33a97b5814d36ddd65ad678ad07ce43b1a67f159/raspberry-pi/4/pkgs-overlays.nix#L5
+final: prev: {
+  deviceTree =
+    prev.deviceTree
+    // {
+      applyOverlays = base: overlays':
+        final.stdenvNoCC.mkDerivation {
+          name = "device-tree-overlays";
+          nativeBuildInputs = with final; [dtc libraspberrypi];
+          buildCommand = let
+            overlays = final.lib.toList overlays';
+          in ''
+            mkdir -p $out
+            cd "${base}"
+            find . -type f -name '*.dtb' -print0 \
+              | xargs -0 cp -v --no-preserve=mode --target-directory "$out" --parents
+
+            for dtb in $(find "$out" -type f -name '*.dtb'); do
+              dtbCompat=$(fdtget -t s "$dtb" / compatible 2>/dev/null || true)
+              # skip files without `compatible` string
+              test -z "$dtbCompat" && continue
+
+              ${final.lib.concatMapStringsSep "\n" (o: ''
+                overlayCompat="$(fdtget -t s "${o.dtboFile}" / compatible)"
+
+                # skip incompatible and non-matching overlays
+                if ! { [[ "$dtbCompat" =~ "$overlayCompat" ]] || [[ "$overlayCompat" = brcm,bcm2835 ]]; }; then
+                  echo "Skipping overlay ${o.name}: incompatible with $(basename "$dtb")"
+                elif ${
+                  if ((o.filter or null) == null)
+                  then "false"
+                  else ''
+                    [[ "''${dtb//${o.filter}/}" ==  "$dtb" ]]
+                  ''
+                }
+                then
+                  echo "Skipping overlay ${o.name}: filter does not match $(basename "$dtb")"
+                else
+                  echo -n "Applying overlay ${o.name} to $(basename "$dtb")... "
+                  mv "$dtb"{,.in}
+
+                  # dtmerge requires a .dtbo ext for dtbo files, otherwise it adds it to the given file implicitly
+                  dtboWithExt="$TMPDIR/$(basename "${o.dtboFile}").dtbo"
+                  cp -r ${o.dtboFile} "$dtboWithExt"
+
+                  dtmerge "$dtb.in" "$dtb" "$dtboWithExt"
+
+                  echo "ok"
+                  rm "$dtb.in" "$dtboWithExt"
+                fi
+              '')
+              overlays}
+
+            done'';
+        };
+    };
+}