persistent-vars-storage-bcm2711: adds a Raspberry Pi compatible persistent storage utility

The Morse Micro persistent-vars-storage package is used to load and store certain device
parameters or configuration from non-volatile storage on a device. This is useful for a
more persistent configuration than what is offered by UCI. Typically used for dpp keys.

The bcm2711 version targets Raspberry Pis and pushes this configuration to the on-board
eeprom.

utils/persistent-vars-storage-bcm2711/Makefile

@@ -0,0 +1,35 @@
+#
+# Copyright 2023 Morse Micro
+#
+# This is free software, licensed under the GNU General Public License v2.
+# See /LICENSE for more information.
+#
+
+include $(TOPDIR)/rules.mk
+
+
+PKG_NAME:=persistent-vars-storage-bcm2711
+PKG_RELEASE=1
+
+PKG_MAINTAINER:=Morse Micro
+
+include $(INCLUDE_DIR)/package.mk
+
+define Package/persistent-vars-storage-bcm2711
+	SECTION:=Utilities
+	CATEGORY:=Utilities
+	PROVIDES:=persistent-vars-storage
+	TITLE:=Reads (or maybe writes in future) key-value pairs from(/into) the RPi 4 EEPROM memory
+	DEPENDS:= +bcm27xx-userland @TARGET_bcm27xx_bcm2711
+endef
+
+define Build/Compile
+
+endef
+
+define Package/persistent-vars-storage-bcm2711/install
+	$(INSTALL_DIR) $(1)/sbin
+	$(INSTALL_BIN) ./files/sbin/persistent_vars_storage.sh $(1)/sbin/persistent_vars_storage.sh
+endef
+
+$(eval $(call BuildPackage,persistent-vars-storage-bcm2711))

utils/persistent-vars-storage-bcm2711/files/sbin/persistent_vars_storage.sh

@@ -0,0 +1,53 @@
+#!/bin/sh
+#
+# Copyright (C) 2023 MorseMicro
+#
+
+
+operation="$1"
+key="$2"
+value="$3"
+
+set -eu
+
+get_key_from_persistent_storage()
+{
+    local config_key=
+    config_key=$(vcgencmd bootloader_config | grep "$key=")
+    config_key=$(echo "$config_key" | sed "s/$key=//g")
+    echo "$config_key"
+}
+
+print_usage()
+{
+    echo "persistent_vars_storage.sh OPERATION(READ|WRITE|ERASE) KEY [VALUE]" 1>&2;
+}
+
+
+
+case "$operation" in
+    READ)
+        value=$(get_key_from_persistent_storage)
+        if [ -n "$value" ]; then
+            echo "$value"
+            exit 0
+        else
+            echo "The key \"$key\" doesn't exist in bootloader config." 1>&2;
+            print_usage
+            exit 1
+        fi
+    ;;
+
+    WRITE|ERASE)
+        echo "Writing to persistent memory isn't implemented on bcm2711, yet." 1>&2;
+        exit 1
+    ;;
+
+    *)
+        print_usage
+        exit 1
+    ;;
+
+esac
+
+