update comment

stepmania/src/arch/InputHandler/InputHandler.h

@@ -6,13 +6,21 @@
  * will be called during the input update; the derived class should
  * send appropriate events to InputHandler. 
  *
+ * Note that, if the underlying device is capable of it, you're free to
+ * start a blocking thread; just store inputs in your class and send them
+ * off in a batch on the next Update.  Later on, this method will let us
+ * get much more accurate timestamps, especially if we have access to realtime
+ * threading: we can get events more quickly and timestamp them, instead of
+ * having a rough timing granularity due to the framerate.  We can't do this
+ * with SDL, though.
+ *
  * Send input events for a specific type of device.  Only one driver
  * for a given set of InputDevice types should be loaded for a given
  * arch.  For example, any number of drivers may produce DEVICE_PUMPn
- * events, but only one may be loaded at a time.
- *
- * DEVICE_KEYBOARD and DEVICE_JOYn are fed from SDL and should not
- * be used by RageInputFeeders.
+ * events, but only one may be loaded at a time.  (This will be inconvenient
+ * if, for example, we have two completely distinct methods of getting
+ * input for the same device; we have no method to allocate device numbers.
+ * We don't need this now; I'll write it if it becomes needed.)
  */
 
 class InputHandler