libcamera: ipa_data_serializer: Add specialization for enums

Instead of handling enums specially in the code generation templates,
create a specialization of `IPADataSerializer` that handles enums.

Every enum is serialized as a `uint32_t`, with `static_assert` to
ensure that every possible value fits. Previously, enums were
(de)serialized in `(de)serializer_field()` based on the size of
their underlying types. Afer this change, every enum is uniformly
handled as a `uint32_t`.

Signed-off-by: Barnabás Pőcze <barnabas.pocze@ideasonboard.com>
Reviewed-by: Paul Elder <paul.elder@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>

include/libcamera/internal/ipa_data_serializer.h

@@ -61,7 +61,7 @@ T readPOD(std::vector<uint8_t> &vec, size_t pos)
 
 } /* namespace */
 
-template<typename T>
+template<typename T, typename = void>
 class IPADataSerializer
 {
 public:
@@ -344,6 +344,52 @@ public:
 	}
 };
 
+template<typename E>
+class IPADataSerializer<E, std::enable_if_t<std::is_enum_v<E>>>
+{
+	using U = uint32_t;
+	static_assert(sizeof(E) <= sizeof(U));
+
+public:
+	static std::tuple<std::vector<uint8_t>, std::vector<SharedFD>>
+	serialize(const E &data, [[maybe_unused]] ControlSerializer *cs = nullptr)
+	{
+		std::vector<uint8_t> dataVec;
+		appendPOD<U>(dataVec, static_cast<U>(data));
+
+		return { dataVec, {} };
+	}
+
+	static E deserialize(std::vector<uint8_t> &data,
+			     [[maybe_unused]] ControlSerializer *cs = nullptr)
+	{
+		return deserialize(data.cbegin(), data.cend());
+	}
+
+	static E deserialize(std::vector<uint8_t>::const_iterator dataBegin,
+			     std::vector<uint8_t>::const_iterator dataEnd,
+			     [[maybe_unused]] ControlSerializer *cs = nullptr)
+	{
+		return static_cast<E>(readPOD<U>(dataBegin, 0, dataEnd));
+	}
+
+	static E deserialize(std::vector<uint8_t> &data,
+			     [[maybe_unused]] std::vector<SharedFD> &fds,
+			     [[maybe_unused]] ControlSerializer *cs = nullptr)
+	{
+		return deserialize(data.cbegin(), data.cend());
+	}
+
+	static E deserialize(std::vector<uint8_t>::const_iterator dataBegin,
+			     std::vector<uint8_t>::const_iterator dataEnd,
+			     [[maybe_unused]] std::vector<SharedFD>::const_iterator fdsBegin,
+			     [[maybe_unused]] std::vector<SharedFD>::const_iterator fdsEnd,
+			     [[maybe_unused]] ControlSerializer *cs = nullptr)
+	{
+		return deserialize(dataBegin, dataEnd);
+	}
+};
+
 #endif /* __DOXYGEN__ */
 
 } /* namespace libcamera */