get_standard_device_mappings for mechdriver

get_mappings for machanism drivers return back different dicts for
different mechanism drivers. By adding get_standard_device_mappings
method SRIOV and OVS mechanism drivers can return a mapping dict in a
form like this one:
{'physnet_name': ['device_or_bridge_1', 'device_or_bridge_2']}

Change-Id: Ieddd9b3a4f3d7269aafc373f040c55b025f5c201
Related-Bug: #1578989

neutron/plugins/ml2/drivers/mech_sriov/mech_driver/mech_driver.py

@@ -22,6 +22,7 @@ from oslo_config import cfg
 
 from oslo_log import log
 
+from neutron._i18n import _
 from neutron.conf.plugins.ml2.drivers.mech_sriov import mech_sriov_conf
 from neutron.plugins.ml2.drivers import mech_agent
 from neutron.plugins.ml2.drivers.mech_sriov.mech_driver \
@@ -89,6 +90,23 @@ class SriovNicSwitchMechanismDriver(mech_agent.SimpleAgentMechanismDriverBase):
     def get_mappings(self, agent):
         return agent['configurations'].get('device_mappings', {})
 
+    def get_standard_device_mappings(self, agent):
+        """Return the agent's device mappings in a standard way.
+
+        The common format for OVS and SRIOv mechanism drivers:
+        {'physnet_name': ['device_or_bridge_1', 'device_or_bridge_2']}
+
+        :param agent: The agent
+        :returns A dict in the format: {'physnet_name': ['bridge_or_device']}
+        :raises ValueError: if there is no device_mappings key in
+                            agent['configurations']
+        """
+        if 'device_mappings' in agent['configurations']:
+            return agent['configurations']['device_mappings']
+        else:
+            raise ValueError(_('Cannot standardize device mappings of agent '
+                               'type: %s'), agent['agent_type'])
+
     def bind_port(self, context):
         LOG.debug("Attempting to bind port %(port)s on "
                   "network %(network)s",

neutron/plugins/ml2/drivers/openvswitch/mech_driver/mech_openvswitch.py

@@ -23,6 +23,7 @@ from neutron_lib import constants
 from oslo_config import cfg
 from oslo_log import log
 
+from neutron._i18n import _
 from neutron.agent import securitygroups_rpc
 from neutron.conf.plugins.ml2.drivers.openvswitch import mech_ovs_conf
 from neutron.plugins.ml2.drivers import mech_agent
@@ -90,6 +91,24 @@ class OpenvswitchMechanismDriver(mech_agent.SimpleAgentMechanismDriverBase):
     def get_mappings(self, agent):
         return agent['configurations'].get('bridge_mappings', {})
 
+    def get_standard_device_mappings(self, agent):
+        """Return the agent's bridge mappings in a standard way.
+
+        The common format for OVS and SRIOv mechanism drivers:
+        {'physnet_name': ['device_or_bridge_1', 'device_or_bridge_2']}
+
+        :param agent: The agent
+        :returns A dict in the format: {'physnet_name': ['bridge_or_device']}
+        :raises ValueError: if there is no bridge_mappings key in
+                            agent['configurations']
+        """
+        if 'bridge_mappings' in agent['configurations']:
+            return {k: [v] for k, v in
+                    agent['configurations']['bridge_mappings'].items()}
+        else:
+            raise ValueError(_('Cannot standardize bridge mappings of agent '
+                               'type: %s'), agent['agent_type'])
+
     def check_vlan_transparency(self, context):
         """Currently Openvswitch driver doesn't support vlan transparency."""
         return False

neutron/tests/unit/plugins/ml2/drivers/mech_sriov/mech_driver/test_mech_sriov_nic_switch.py

@@ -270,3 +270,16 @@ class SriovSwitchMechVnicTypesTestCase(SriovNicSwitchMechanismBaseTestCase):
 
         self.assertRaises(ValueError,
                           mech_driver.SriovNicSwitchMechanismDriver)
+
+
+class SriovSwitchDeviceMappingsTestCase(SriovNicSwitchMechanismBaseTestCase):
+
+    def test_standard_device_mappings(self):
+        mappings = self.driver.get_standard_device_mappings(self.AGENTS[0])
+        self.assertDictEqual(self.GOOD_CONFIGS['device_mappings'], mappings)
+
+    def test_standard_device_mappings_negative(self):
+        fake_agent = {'agent_type': constants.AGENT_TYPE_NIC_SWITCH,
+                      'configurations': {}}
+        self.assertRaises(ValueError, self.driver.get_standard_device_mappings,
+                          fake_agent)

neutron/tests/unit/plugins/ml2/drivers/openvswitch/mech_driver/test_mech_openvswitch.py

@@ -355,3 +355,21 @@ class OpenvswitchMechVnicTypesTestCase(OpenvswitchMechanismBaseTestCase):
 
         self.assertRaises(ValueError,
                           mech_openvswitch.OpenvswitchMechanismDriver)
+
+
+class OpenvswitchMechDeviceMappingsTestCase(OpenvswitchMechanismBaseTestCase):
+
+    def test_standard_device_mappings(self):
+        mappings = self.driver.get_standard_device_mappings(self.AGENTS[0])
+        self.assertEqual(
+            len(self.GOOD_CONFIGS['bridge_mappings']),
+            len(mappings))
+        for ph_orig, br_orig in self.GOOD_CONFIGS['bridge_mappings'].items():
+            self.assertIn(ph_orig, mappings)
+            self.assertEqual([br_orig], mappings[ph_orig])
+
+    def test_standard_device_mappings_negative(self):
+        fake_agent = {'agent_type': constants.AGENT_TYPE_OVS,
+                      'configurations': {}}
+        self.assertRaises(ValueError, self.driver.get_standard_device_mappings,
+                          fake_agent)

releasenotes/notes/get_standard_device_mappings_for_mechdriver-bc039d478ea0b162.yaml

@@ -0,0 +1,7 @@
+---
+features:
+  - |
+    Add get_standard_device_mappings to SriovNicSwitchMechanismDriver and
+    OpenvswitchMechanismDriver so they can return the interface or bridge
+    mappings in a standard way. The common format is a dict like:
+    {'physnet_name': ['device_or_bridge_1', 'device_or_bridge_2']}.