fastrpc: libhexagonrpc: add remote method definition macro

This macro used for the interfaces in hexagonrpcd are useful for
anything using the fastrpc function. Add the macro in the exported
headers so other applications using libhexagonrpc can define remote
methods easily.

fastrpc/include/libhexagonrpc/interface.h

@@ -0,0 +1,54 @@
+/*
+ * FastRPC interface method definition macros
+ *
+ * Copyright (C) 2023 Richard Acayan
+ *
+ * This file is part of sensh.
+ *
+ * Sensh is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#ifndef LIBHEXAGONRPC_INTERFACE_H
+#define LIBHEXAGONRPC_INTERFACE_H
+
+#include <libhexagonrpc/fastrpc.h>
+
+/*
+ * We want to declare method definitions as external by default so we only need
+ * special flags when compiling the interfaces. Otherwise, everything that uses
+ * the interfaces would need to define a macro.
+ */
+#if !HEXAGONRPC_BUILD_METHOD_DEFINITIONS
+
+#define HEXAGONRPC_DEFINE_REMOTE_METHOD(mid, name,			\
+					innums, inbufs,			\
+					outnums, outbufs)		\
+	extern const struct fastrpc_function_def_interp2 name##_def;
+
+#else /* HEXAGONRPC_BUILD_METHOD_DEFINITIONS */
+
+#define HEXAGONRPC_DEFINE_REMOTE_METHOD(mid, name,			\
+					innums, inbufs,			\
+					outnums, outbufs)		\
+	const struct fastrpc_function_def_interp2 name##_def = {	\
+		.msg_id = mid,						\
+		.in_nums = innums,					\
+		.in_bufs = inbufs,					\
+		.out_nums = outnums,					\
+		.out_bufs = outbufs,					\
+	};
+
+#endif /* HEXAGONRPC_BUILD_METHOD_DEFINITIONS */
+
+#endif /* LIBHEXAGONRPC_INTERFACE_H */