fdt-forward: Init tool to copy FDT nodes and props

Will be used by stage-0 to forward nodes that are required.

overlay/mobile-nixos/fdt-forward/default.nix

@@ -0,0 +1,10 @@
+{ runCommandNoCC, runtimeShell, lib, dtc, ubootTools }:
+
+runCommandNoCC "fdt-forward" {} ''
+  mkdir -p $out/bin
+  echo "#!${runtimeShell}" > $out/bin/fdt-forward
+  cat "${./fdt-forward.sh}" >> $out/bin/fdt-forward
+  chmod +x $out/bin/fdt-forward
+  substituteInPlace $out/bin/fdt-forward \
+    --replace @PATH@ "${lib.makeBinPath [ dtc ubootTools ]}"
+''

overlay/mobile-nixos/fdt-forward/fdt-forward.sh

@@ -0,0 +1,104 @@
+#!/bin/sh
+
+# By default, it will use `/sys/firmware/fdt` as a source to forward from.
+# The source can be overriden using the FDT variable, or `--fdt`.
+#
+# Example usage:
+#
+# fdt-forward \
+#	--print-header \
+#	--copy-dtb "./desired-dtb.dtb" \
+#	--forward-node "/memory" \
+#	--forward-prop "/" "serial-number" \
+#	--forward-prop "/soc/mmc@1c10000/wifi@1" "local-mac-address" \
+#	  | fdt-forward --to-dtb > out.dtb
+
+set -e
+set -u
+
+PATH="@PATH@:$PATH"
+
+
+# shellcheck disable=2120
+to_dts() {
+	dtc --sort -I dtb -O dts "$@"
+}
+
+# shellcheck disable=2120
+to_dtb() {
+	dtc --sort -I dts -O dtb "$@"
+}
+
+# Functions with `__` prefixed names are expected to
+# be called from `run`, replacing `-` with `_`.
+
+# `--to-dts` will not continue execution further.
+# It is a convenience function for calling `dtc`.
+__to_dts() {
+	to_dts "$@"
+}
+
+# `--to-dtb` will not continue execution further.
+# It is a convenience function for calling `dtc`.
+__to_dtb() {
+	to_dtb "$@"
+}
+
+# Print a device tree header.
+__print_header() {
+	printf '/dts-v1/;\n'
+	run "$@"
+}
+
+# Forwards the *whole* node
+__forward_node() {
+	node="$1"; shift
+
+	printf '\n// forwarded node: "%s"\n' "$node"
+	fdtgrep --show-subnodes --include-node "$node" "$FDT"
+	run "$@"
+}
+
+# Forwards the prop matching the name from the given node.
+__forward_prop() {
+	node="$1"; shift
+	prop="$1"; shift
+
+	printf '\n// forwarded prop: "%s" from node: "%s"\n' "$prop" "$node"
+	# In order, we get the node (without descendents!) as dts
+	# Synthesize it back into dtb
+	# Then we can get the desired prop.
+	fdtgrep --show-version --include-node "$node" "$FDT" \
+		| to_dtb \
+		| fdtgrep "$prop" -
+
+	# Doing otherwise would give us *all* matching prop names,
+	# and not exclusively the one for the desired node.
+	run "$@"
+}
+
+# Copy the whole dtb as dts source.
+# Its header will be stripped.
+__copy_dtb() {
+	dtb="$1"; shift
+	printf '\n// Initial dtb copy...\n'
+	to_dts "$dtb" | tail -n+2
+	run "$@"
+}
+
+__fdt() {
+	FDT="$1"; shift
+	run "$@"
+}
+
+
+FDT="${FDT:-/sys/firmware/fdt}"
+
+run() {
+	if [ $# -gt 0 ]; then
+		cmd="${1//-/_}"; shift
+		"$cmd" "$@"
+	fi
+}
+
+run "$@"

overlay/overlay.nix

@@ -112,6 +112,8 @@ in
       boot-recovery-menu-simulator = callPackage ../boot/recovery-menu/simulator.nix {};
       boot-splash-simulator = callPackage ../boot/splash/simulator.nix {};
 
+      fdt-forward = callPackage ./mobile-nixos/fdt-forward {};
+
       map-dtbs = callPackage ./mobile-nixos/map-dtbs {};
     };