Initial sketch for the generic data-transfer interface.

src/include/gpxe/interface.h

@@ -0,0 +1,36 @@
+#ifndef _GPXE_INTERFACE_H
+#define _GPXE_INTERFACE_H
+
+/** @file
+ *
+ * Object communication interfaces
+ *
+ */
+
+/** An object communication interface */
+struct interface {
+	/** Destination interface
+	 *
+	 * When messages are sent via this interface, they will be
+	 * delivered to the destination interface.
+	 *
+	 * This pointer may never be NULL.  When the interface is
+	 * unplugged, it should point to a null interface.
+	 */
+	struct interface *dest;
+	/** Update reference count
+	 *
+	 * @v intf		Interface
+	 * @v delta		Change to apply to reference count
+	 *
+	 * This method updates the reference count for the object
+	 * containing the interface.
+	 */
+	void ( * refcnt ) ( struct interface *intf, int delta );
+};
+
+extern void plug ( struct interface *intf, struct interface *dest );
+
+extern void null_refcnt ( struct interface *intf, int delta );
+
+#endif /* _GPXE_INTERFACE_H */