[ioapi] Formalise the I/O API as used in i386-pcbios

1 files changed, 82 insertions, 0 deletions

diff --git a/src/include/gpxe/api.h b/src/include/gpxe/api.h
new file mode 100644
index 000000000..df5d1ae3e
--- /dev/null
+++ b/src/include/gpxe/api.h
@@ -0,0 +1,82 @@
+#ifndef _GPXE_API_H
+#define _GPXE_API_H
+
+/** @file
+ *
+ * gPXE internal APIs
+ *
+ * There are various formally-defined APIs internal to gPXE, with
+ * several differing implementations specific to particular execution
+ * environments (e.g. PC BIOS, EFI, LinuxBIOS).
+ *
+ */
+
+/** @defgroup Single-implementation APIs
+ *
+ * These are APIs for which only a single implementation may be
+ * compiled in at any given time.
+ *
+ * @{
+ */
+
+/**
+ * Calculate function implementation name
+ *
+ * @v _prefix		Subsystem prefix
+ * @v _api_func		API function
+ * @ret _subsys_func	Subsystem API function
+ *
+ * The subsystem prefix should be an empty string for the currently
+ * selected subsystem, and should be a subsystem-unique string for all
+ * other subsystems.
+ */
+#define SINGLE_API_NAME( _prefix, _api_func ) _prefix ## _api_func
+
+/**
+ * Calculate static inline function name
+ *
+ * @v _prefix		Subsystem prefix
+ * @v _api_func		API function
+ * @ret _subsys_func	Subsystem API function
+ */
+#define SINGLE_API_INLINE( _prefix, _api_func )	\
+	SINGLE_API_NAME ( _prefix, _api_func )
+
+/**
+ * Provide an API implementation
+ *
+ * @v _prefix		Subsystem prefix
+ * @v _api_func		API function
+ * @v _func		Implementing function
+ */
+#define PROVIDE_SINGLE_API( _prefix, _api_func, _func )			      \
+	/* Ensure that _api_func exists */				      \
+	typeof ( _api_func ) _api_func;					      \
+	/* Ensure that _func exists */					      \
+	typeof ( _func ) _func;						      \
+	/* Ensure that _func is type-compatible with _api_func */	      \
+	typeof ( _api_func ) _func;					      \
+	/* Ensure that _subsys_func is non-static */			      \
+	extern typeof ( _api_func ) SINGLE_API_NAME ( _prefix, _api_func );   \
+	/* Provide symbol alias from _subsys_func to _func */		      \
+	typeof ( _api_func ) SINGLE_API_NAME ( _prefix, _api_func )	      \
+		__attribute__ (( alias ( #_func ) ));
+
+/**
+ * Provide a static inline API implementation
+ *
+ * @v _prefix		Subsystem prefix
+ * @v _api_func		API function
+ */
+#define PROVIDE_SINGLE_API_INLINE( _prefix, _api_func )			      \
+	/* Ensure that _api_func exists */				      \
+	typeof ( _api_func ) _api_func;					      \
+	/* Ensure that _subsys_func exists and is static */		      \
+	static typeof ( SINGLE_API_INLINE ( _prefix, _api_func ) )	      \
+		SINGLE_API_INLINE ( _prefix, _api_func );		      \
+	/* Ensure that _subsys_func is type-compatible with _api_func */      \
+	typeof ( _api_func ) SINGLE_API_INLINE ( _prefix, _api_func );
+
+/** @} */
+
+#endif /* _GPXE_API_H */