mpm: PeriphManagerBase: List all sync-related methods

All PeriphManagerBase childs need to implement

- get_{clock,time,sync}_source()
- get_{clock,time,sync}_sources()
- set_{clock,time,sync}_source()

So we populate PeriphManagerBase with defaults for all of those.

mpm/python/usrp_mpm/periph_manager/base.py

@@ -1216,6 +1216,14 @@ class PeriphManagerBase(object):
     #######################################################################
     # Sync API
     #######################################################################
+    def get_clock_source(self):
+        " Returns the currently selected clock source "
+        raise NotImplementedError("get_clock_source() not available on this device!")
+
+    def get_time_source(self):
+        " Returns the currently selected time source "
+        raise NotImplementedError("get_time_source() not available on this device!")
+
     def get_sync_source(self):
         """
         Gets the current time and clock source
@@ -1225,6 +1233,57 @@ class PeriphManagerBase(object):
             "clock_source": self.get_clock_source(),
         }
 
+    def get_clock_sources(self):
+        """
+        Returns a list of valid clock sources. This is a list of strings.
+        """
+        self.log.warning("get_clock_sources() was not specified for this device!")
+        return []
+
+    def get_time_sources(self):
+        """
+        Returns a list of valid time sources. This is a list of strings.
+        """
+        self.log.warning("get_time_sources() was not specified for this device!")
+        return []
+
+    def get_sync_sources(self):
+        """
+        Returns a list of valid sync sources. This is a list of dictionaries.
+        """
+        self.log.warning("get_sync_sources() was not specified for this device!")
+        return []
+
+    def set_clock_source(self, *args):
+        """
+        Set a clock source.
+
+        The choice to allow arbitrary arguments is based on historical decisions
+        and backward compatibility. UHD/mpmd will call this with a single argument,
+        so args[0] is the clock source (as a string).
+        """
+        raise NotImplementedError("set_clock_source() not available on this device!")
+
+    def set_time_source(self, time_source):
+        " Set a time source "
+        raise NotImplementedError("set_time_source() not available on this device!")
+
+    def set_sync_source(self, sync_args):
+        """
+        If a device has no special code for setting the sync-source atomically,
+        we simply forward these settings to set_clock_source() and set_time_source()
+        (in that order).
+        """
+        if sync_args not in self.get_sync_sources():
+            sync_args_str = \
+                ','.join([str(k) + '=' + str(v) for k, v in sync_args.items()])
+            self.log.warn(
+                f"Attempting to set unrecognized Sync source {sync_args_str}!")
+        clock_source = sync_args.get('clock_source', self.get_clock_source())
+        time_source = sync_args.get('time_source', self.get_time_source())
+        self.set_clock_source(clock_source)
+        self.set_time_source(time_source)
+
     ###########################################################################
     # Clock/Time API
     ###########################################################################