From: Luke Kenneth Casson Leighton <lkcl@lkcl.net>
Date: Sat, 20 Jun 2020 00:04:02 +0000 (+0100)
Subject: more declaration of singleton objects
X-Git-Tag: 24jan2021_ls180~12
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=5136791f5980dbd69518412d77ee7e3d897287c4;p=nmigen-soc.git

more declaration of singleton objects
---

diff --git a/nmigen_soc/wishbone/bus.py b/nmigen_soc/wishbone/bus.py
index 2d9296c..580af84 100644
--- a/nmigen_soc/wishbone/bus.py
+++ b/nmigen_soc/wishbone/bus.py
@@ -225,8 +225,11 @@ class Decoder(Elaboratable):
         Bus providing access to subordinate buses.
     """
 
-    def __init__(self, *, addr_width, data_width, granularity=None, features=frozenset(),
+    def __init__(self, *, addr_width, data_width, granularity=None,
+                features=None,
                  alignment=0):
+        if features is None:
+            features = frozenset()
         self.bus = Interface(addr_width=addr_width, data_width=data_width,
                              granularity=granularity, features=features,
                              alignment=alignment)
@@ -373,8 +376,11 @@ class Arbiter(Elaboratable):
         Shared bus to which the selected initiator gains access.
     """
 
-    def __init__(self, *, addr_width, data_width, granularity=None, features=frozenset(),
+    def __init__(self, *, addr_width, data_width, granularity=None,
+                features=None,
                  scheduler="rr"):
+        if features is None:
+            features = frozenset()
         self.bus = Interface(addr_width=addr_width, data_width=data_width,
                              granularity=granularity, features=features)
         self._itors = []