Provide access to chassis identify

Enable command method to turn on identify with full access
to duration and indefinite control.  Note that there is no method
to retrieve it, as the specification does not provide that capability.

Change-Id: I3478101ed4db15232842b508a42aeb9ec9285434

pyghmi/ipmi/command.py

@@ -300,6 +300,39 @@ class Command(object):
         powerstate = 'on' if (response['data'][0] & 1) else 'off'
         return {'powerstate': powerstate}
 
+    def set_identify(self, on=True, duration=None):
+        """Request identify light
+
+        Request the identify light to turn off, on for a duration,
+        or on indefinitely.  Other than error exceptions,
+
+        :param on: Set to True to force on or False to force off
+        :param duration: Set if wanting to request turn on for a duration
+                         rather than indefinitely on
+        """
+        if duration is not None:
+            duration = int(duration)
+            if duration > 255:
+                duration = 255
+            if duration < 0:
+                duration = 0
+            response = self.raw_command(netfn=0, command=4, data=[duration])
+            if 'error' in response:
+                raise exc.IpmiException(response['error'])
+            return
+        forceon = 0
+        if on:
+            forceon = 1
+        if self.ipmi_session.ipmiversion < 2.0:
+            # ipmi 1.5 made due with just one byte, make best effort
+            # to imitate indefinite as close as possible
+            identifydata = [255 * forceon]
+        else:
+            identifydata = [0, forceon]
+        response = self.raw_command(netfn=0, command=4, data=identifydata)
+        if 'error' in response:
+            raise exc.IpmiException(response['error'])
+
     def get_health(self):
         """Summarize health of managed system