diff --git a/src/main/scala/util/Misc.scala b/src/main/scala/util/Misc.scala
index 8ff24fb9..14a2510d 100644
--- a/src/main/scala/util/Misc.scala
+++ b/src/main/scala/util/Misc.scala
@@ -35,6 +35,11 @@ trait DontTouch {
     self.getModulePorts.foreach(dontTouch(_))
     self
   }
+
+  def dontTouchPortsExcept(f: Data => Boolean): this.type = {
+    self.getModulePorts.filterNot(f).foreach(dontTouch(_))
+    self
+  }
 }
 
 trait Clocked extends Bundle {