diff --git a/functions.hpp b/functions.hpp
new file mode 100644
index 0000000..f7511aa
--- /dev/null
+++ b/functions.hpp
@@ -0,0 +1,49 @@
+#include <filesystem>
+#include <functional>
+#include <map>
+#include <memory>
+#include <string>
+#include <variant>
+#include <vector>
+
+namespace sdbusplus
+{
+namespace bus
+{
+class bus;
+} // namespace bus
+} // namespace sdbusplus
+
+namespace sdeventplus
+{
+class Event;
+} // namespace sdeventplus
+
+namespace functions
+{
+namespace process_hostfirmware
+{
+using ErrorCallbackType =
+    std::function<void(const std::filesystem::path&, std::error_code&)>;
+using LinkCallbackType =
+    std::function<void(const std::filesystem::path&,
+                       const std::filesystem::path&, const ErrorCallbackType&)>;
+using MaybeCallCallbackType =
+    std::function<void(const std::vector<std::string>&)>;
+bool getExtensionsForIbmCompatibleSystem(
+    const std::map<std::string, std::vector<std::string>>&,
+    const std::vector<std::string>&, std::vector<std::string>&);
+void writeLink(const std::filesystem::path&, const std::filesystem::path&,
+               const ErrorCallbackType&);
+void findLinks(const std::filesystem::path&, const std::vector<std::string>&,
+               const ErrorCallbackType&, const LinkCallbackType&);
+bool maybeCall(
+    const std::map<
+        std::string,
+        std::map<std::string, std::variant<std::vector<std::string>>>>&,
+    const MaybeCallCallbackType&);
+std::shared_ptr<void> processHostFirmware(
+    sdbusplus::bus::bus&, std::map<std::string, std::vector<std::string>>,
+    std::filesystem::path, ErrorCallbackType, sdeventplus::Event&);
+} // namespace process_hostfirmware
+} // namespace functions