Initial sketch for the generic data-transfer interface.

src/core/xfer.c

@@ -0,0 +1,74 @@
+/*
+ * Copyright (C) 2007 Michael Brown <mbrown@fensystems.co.uk>.
+ *
+ * This program 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 2 of the
+ * License, or 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, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#include <errno.h>
+#include <gpxe/xfer.h>
+
+/** @file
+ *
+ * Data transfer interfaces
+ *
+ */
+
+/**
+ * Deliver datagram
+ *
+ * @v xfer		Data-transfer interface
+ * @v iobuf		Datagram I/O buffer
+ * @ret rc		Return status code
+ */
+int deliver ( struct xfer_interface *xfer, struct io_buffer *iobuf ) {
+	struct xfer_interface *dest = xfer_dest ( xfer );
+
+	return dest->op->deliver ( dest, xfer, iobuf );
+}
+
+/**
+ * Null deliver datagram
+ *
+ * @v xfer		Data-transfer interface
+ * @v src		Source interface
+ * @v iobuf		Datagram I/O buffer
+ * @ret rc		Return status code
+ */
+static int null_deliver ( struct xfer_interface *xfer __unused,
+			  struct xfer_interface *src __unused,
+			  struct io_buffer *iobuf ) {
+	free_iob ( iobuf );
+	return -EPIPE;
+}
+
+/** Null data transfer interface operations */
+struct xfer_interface_operations null_xfer_ops = {
+	.deliver = null_deliver,
+};
+
+/**
+ * Null data transfer interface
+ *
+ * This is the interface to which data transfer interfaces are
+ * connected when unplugged.  It will never generate messages, and
+ * will silently absorb all received messages.
+ */
+struct xfer_interface null_xfer = {
+	.intf = {
+		.dest = &null_xfer.intf,
+		.refcnt = null_refcnt,
+	},
+	.op = &null_xfer_ops,
+};