Provide extensibility to sensors by OEM

OEMs frequently employ special commands for data that logically
would be expected to manifest as a sensor.  Provide a facility
for OEMs to make up sensors and provide data in the form of a
'sensor' without requiring SDR.

Change-Id: I6bce99680ff64ffe2dbc0898d193a17dde066b9c

pyghmi/ipmi/command.py

@@ -550,7 +550,8 @@ class Command(object):
                     raise exc.IpmiException(rsp['error'], rsp['code'])
                 return self._sdr.sensors[sensor].decode_sensor_reading(
                     rsp['data'])
-        raise Exception('Sensor not found: ' + sensorname)
+        self.oem_init()
+        return self._oem.get_sensor_reading(sensorname)
 
     def get_sensor_data(self):
         """Get sensor reading objects
@@ -569,6 +570,9 @@ class Command(object):
                     continue
                 raise exc.IpmiException(rsp['error'], code=rsp['code'])
             yield self._sdr.sensors[sensor].decode_sensor_reading(rsp['data'])
+        self.oem_init()
+        for reading in self._oem.get_sensor_data():
+            yield reading
 
     def get_sensor_descriptions(self):
         """Get available sensor names
@@ -582,6 +586,9 @@ class Command(object):
         for sensor in self._sdr.get_sensor_numbers():
             yield {'name': self._sdr.sensors[sensor].name,
                    'type': self._sdr.sensors[sensor].sensor_type}
+        self.oem_init()
+        for sensor in self._oem.get_sensor_descriptions():
+            yield sensor
 
     def get_network_channel(self):
         """Get a reasonable 'default' network channel.

pyghmi/ipmi/oem/generic.py

@@ -52,6 +52,33 @@ class OEMHandler(object):
         """
         return ()
 
+    def get_sensor_reading(self, sensorname):
+        """Get an OEM sensor
+
+        If software wants to model some OEM behavior as a 'sensor' without
+        doing SDR, this hook provides that ability.  It should mimic
+        the behavior of 'get_sensor_reading' in command.py.
+        """
+        raise Exception('Sensor not found: ' + sensorname)
+
+    def get_sensor_descriptions(self):
+        """Get list of OEM sensor names and types
+
+        Iterate over dicts describing a label and type for OEM 'sensors'.  This
+        should mimic the behavior of the get_sensor_descriptions function
+        in command.py.
+        """
+        return ()
+
+    def get_sensor_data(self):
+        """Get OEM sensor data
+
+        Iterate through all OEM 'sensors' and return data as if they were
+        normal sensors.  This should mimic the behavior of the get_sensor_data
+        function in command.py.
+        """
+        return ()
+
     def get_oem_inventory(self):
         """Get tuples of component names and inventory data.