xen: Add module alias to autoload backend drivers

All the Xen backend drivers are assigned to a special bus type
xen-backend. This patch exports xen-backend:* names through modalias and
uevent to autoload them.
Signed-off-by: Bastian Blank <waldi@debian.org>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

drivers/xen/xenbus/xenbus_probe.c

@@ -393,7 +393,8 @@ static ssize_t devtype_show(struct device *dev,
 static ssize_t modalias_show(struct device *dev,
 			     struct device_attribute *attr, char *buf)
 {
-	return sprintf(buf, "xen:%s\n", to_xenbus_device(dev)->devicetype);
+	return sprintf(buf, "%s:%s\n", dev->bus->name,
+		       to_xenbus_device(dev)->devicetype);
 }
 
 struct device_attribute xenbus_dev_attrs[] = {

drivers/xen/xenbus/xenbus_probe_backend.c

@@ -107,6 +107,9 @@ static int xenbus_uevent_backend(struct device *dev,
 	if (xdev == NULL)
 		return -ENODEV;
 
+	if (add_uevent_var(env, "MODALIAS=xen-backend:%s", xdev->devicetype))
+		return -ENOMEM;
+
 	/* stuff we want to pass to /sbin/hotplug */
 	if (add_uevent_var(env, "XENBUS_TYPE=%s", xdev->devicetype))
 		return -ENOMEM;