Add xenbus_for_each_[back,front]end functions to iterate each bus

diff -r 4f67d849e788 linux-2.6-xen-sparse/drivers/xen/xenbus/xenbus_probe.c
--- a/linux-2.6-xen-sparse/drivers/xen/xenbus/xenbus_probe.c	Tue Apr 03 09:03:51 2007 +0100
+++ b/linux-2.6-xen-sparse/drivers/xen/xenbus/xenbus_probe.c	Tue Apr 03 13:32:33 2007 +0100
@@ -4,6 +4,7 @@
  * Copyright (C) 2005 Rusty Russell, IBM Corporation
  * Copyright (C) 2005 Mike Wray, Hewlett-Packard
  * Copyright (C) 2005, 2006 XenSource Ltd
+ * Copyright (C) 2007 Solarflare Communications, Inc.
  * 
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License version 2
@@ -1079,3 +1080,10 @@ static int __init boot_wait_for_devices(
 
 late_initcall(boot_wait_for_devices);
 #endif
+
+
+int xenbus_for_each_frontend(void *arg, int (*fn)(struct device *, void *))
+{
+        return bus_for_each_dev(&xenbus_frontend.bus, NULL, arg, fn);
+}
+EXPORT_SYMBOL_GPL(xenbus_for_each_frontend);
diff -r 4f67d849e788 linux-2.6-xen-sparse/drivers/xen/xenbus/xenbus_probe_backend.c
--- a/linux-2.6-xen-sparse/drivers/xen/xenbus/xenbus_probe_backend.c	Tue Apr 03 09:03:51 2007 +0100
+++ b/linux-2.6-xen-sparse/drivers/xen/xenbus/xenbus_probe_backend.c	Tue Apr 03 13:32:33 2007 +0100
@@ -4,6 +4,7 @@
  * Copyright (C) 2005 Rusty Russell, IBM Corporation
  * Copyright (C) 2005 Mike Wray, Hewlett-Packard
  * Copyright (C) 2005, 2006 XenSource Ltd
+ * Copyright (C) 2007 Solarflare Communications, Inc.
  * 
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License version 2
@@ -284,3 +285,10 @@ void xenbus_backend_device_register(void
 		       xenbus_backend.error);
 	}
 }
+
+int xenbus_for_each_backend(void *arg, int (*fn)(struct device *, void *))
+{
+        return bus_for_each_dev(&xenbus_backend.bus, NULL, arg, fn);
+}
+EXPORT_SYMBOL_GPL(xenbus_for_each_backend);
+
diff -r 4f67d849e788 linux-2.6-xen-sparse/include/xen/xenbus.h
--- a/linux-2.6-xen-sparse/include/xen/xenbus.h	Tue Apr 03 09:03:51 2007 +0100
+++ b/linux-2.6-xen-sparse/include/xen/xenbus.h	Tue Apr 03 13:32:33 2007 +0100
@@ -299,4 +299,7 @@ int xenbus_dev_is_online(struct xenbus_d
 int xenbus_dev_is_online(struct xenbus_device *dev);
 int xenbus_frontend_closed(struct xenbus_device *dev);
 
+extern int xenbus_for_each_backend(void *arg, int (*fn)(struct device *, void *));
+extern int xenbus_for_each_frontend(void *arg, int (*fn)(struct device *, void *));
+
 #endif /* _XEN_XENBUS_H */