perf jevents: Add descriptions to metricgroup abstraction

Add a function to recursively generate metric group descriptions.

Signed-off-by: Ian Rogers <irogers@google.com>
Tested-by: Thomas Falcon <thomas.falcon@intel.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>

tools/perf/pmu-events/metric.py

@@ -475,6 +475,8 @@ class Metric:
 
     return result
 
+  def ToMetricGroupDescriptions(self, root: bool = True) -> Dict[str, str]:
+    return {}
 
 class _MetricJsonEncoder(json.JSONEncoder):
   """Special handling for Metric objects."""
@@ -493,10 +495,12 @@ class MetricGroup:
   which can facilitate arrangements similar to trees.
   """
 
-  def __init__(self, name: str, metric_list: List[Union[Metric,
-                                                        'MetricGroup']]):
+  def __init__(self, name: str,
+               metric_list: List[Union[Metric, 'MetricGroup']],
+               description: Optional[str] = None):
     self.name = name
     self.metric_list = metric_list
+    self.description = description
     for metric in metric_list:
       metric.AddToMetricGroup(self)
 
@@ -516,6 +520,12 @@ class MetricGroup:
   def ToPerfJson(self) -> str:
     return json.dumps(sorted(self.Flatten()), indent=2, cls=_MetricJsonEncoder)
 
+  def ToMetricGroupDescriptions(self, root: bool = True) -> Dict[str, str]:
+    result = {self.name: self.description} if self.description else {}
+    for x in self.metric_list:
+      result.update(x.ToMetricGroupDescriptions(False))
+    return result
+
   def __str__(self) -> str:
     return self.ToPerfJson()