cgroups: use subsystems namedtuple in the controllers mounting loop

This is just a simple re-factoring patch in preparation of the following
one. Since we have a list of CGroups subsystems, which includes the
hierarchy ID for each entry, let's use directly these namedtuples in the
mouting loop. The following patch will make use of the hierarchy ID to
properly mount each controller.

Signed-off-by: Patrick Bellasi <patrick.bellasi@arm.com>

devlib/module/cgroups.py

@@ -318,17 +318,17 @@ class CgroupsModule(Module):
         self.cgroup_root = target.path.join(
             target.working_directory, 'cgroups')
 
-        # Load list of available controllers
+        # Get the list of the available controllers
-        controllers = []
         subsys = self.list_subsystems()
-        for (n, h, c, e) in subsys:
+        if len(subsys) == 0:
-            controllers.append(n)
+            self.logger.warning('No CGroups controller available')
-        self.logger.debug('Available controllers: %s', controllers)
+            return
 
         # Initialize controllers
+        self.logger.info('Available controllers:')
         self.controllers = {}
-        for idx in controllers:
+        for ss in subsys:
-            controller = Controller(idx)
+            controller = Controller(ss.name)
             self.logger.debug('Init %s controller...', controller.kind)
             if not controller.probe(self.target):
                 continue
@@ -338,7 +338,7 @@ class CgroupsModule(Module):
                 message = 'cgroups {} controller is not supported by the target'
                 raise TargetError(message.format(controller.kind))
             self.logger.debug('Controller %s enabled', controller.kind)
-            self.controllers[idx] = controller
+            self.controllers[ss.name] = controller
 
     def list_subsystems(self):
         subsystems = []