ec2utils: factor generic helper function into generic place

This patch moves out a helper function, properties_root_device_name(),
into generic file nova/block_device.py.

1 files changed, 35 insertions, 0 deletions

diff --git a/nova/block_device.py b/nova/block_device.py
new file mode 100644
index 000000000..963dffa37
--- /dev/null
+++ b/nova/block_device.py
@@ -0,0 +1,35 @@
+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+
+# Copyright 2011 Isaku Yamahata <yamahata@valinux co jp>
+# All Rights Reserved.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+
+def properties_root_device_name(properties):
+    """get root device name from image meta data.
+    If it isn't specified, return None.
+    """
+    root_device_name = None
+
+    # NOTE(yamahata): see image_service.s3.s3create()
+    for bdm in properties.get('mappings', []):
+        if bdm['virtual'] == 'root':
+            root_device_name = bdm['device']
+
+    # NOTE(yamahata): register_image's command line can override
+    #                 <machine>.manifest.xml
+    if 'root_device_name' in properties:
+        root_device_name = properties['root_device_name']
+
+    return root_device_name