Re: [RFA]: hw-glue-bus-mux selection behavior

[Dave Brolley <brolley at redhat dot com>]

Frank Ch. Eigler wrote:

> Hi -
> 
> On Tue, Mar 27, 2001 at 06:39:47PM -0500, Dave Brolley wrote:
> : [...]
> : Notes:
> : 1)  I actually implemented the selector to choose "downstream1" when the 
> : pin value is even and "downstream2" otherwise. [...]
> 
> To me, this seems like an unnecessary feature; I'd let the client pick
> exactly 0 or 1.

ok -- just trying to be too clever, I guess. How about 0 vs non-zero? I 
think there should be some defined behavior for all values. Updated 
patch attached.

> : 2) I left the mux_passthrough_bus::switch_bus function in since it still 
> : seems like useful functionality for other subclasses.
> 
> Hmm.  For what it's worth, I wouldn't have put the mux_passthrough
> thingie into sid/include/ at all.  It looks like a specialized enough
> piece of code that I'd have kept it inside the source directory of
> the appropriate glue component.

I didn't move it. It was already there. Feel free to move it if you like.

> : OK to commit?
> 
> Sure; up to you if you want to take my mild objections into consideration.

Of course, as always....

Dave
Index: component/glue/glue.cxx
===================================================================
RCS file: /cvs/cvsfiles/devo/sid/component/glue/glue.cxx,v
retrieving revision 1.32
diff -c -p -r1.32 glue.cxx
*** component/glue/glue.cxx	2001/01/12 21:01:31	1.32
--- component/glue/glue.cxx	2001/03/27 23:20:56
*************** public:
*** 540,549 ****
  
    void handle_switch_pin (host_int_4 value)
      {
!       if (value != 0)
!         {
!           upstream.switch_bus();
!         }
      }
  };
  
--- 540,546 ----
  
    void handle_switch_pin (host_int_4 value)
      {
!       upstream.select_bus (value);
      }
  };
  
Index: component/glue/hw-glue-bus-mux.txt
===================================================================
RCS file: /cvs/cvsfiles/devo/sid/component/glue/hw-glue-bus-mux.txt,v
retrieving revision 1.2
diff -c -p -r1.2 hw-glue-bus-mux.txt
*** component/glue/hw-glue-bus-mux.txt	2001/01/12 21:01:31	1.2
--- component/glue/hw-glue-bus-mux.txt	2001/03/27 23:20:56
***************
*** 24,33 ****
        to "downstream1".
  
      * Switching
!       When the "switch" pin is driven high, the output accessor will
!       be switched from the current output accessor to the one not in use.
        The "switch" pin can be driven any number of times, each time
!       causing the output to be switched.
  
      * Bus traffic
        Input to the "upstream" bus is passed on to the current
--- 24,37 ----
        to "downstream1".
  
      * Switching
!       When the "switch" pin is driven with the value zero, the output accessor
!       will be "downstream1". When the "switch" pin is driven with a non-zero
!	value, the output accessor will be "downstream2".
        The "switch" pin can be driven any number of times, each time
!       causing the corresponding output to be selected.
  
      * Bus traffic
        Input to the "upstream" bus is passed on to the current
Index: include/sidbusutil.h
===================================================================
RCS file: /cvs/cvsfiles/devo/sid/include/sidbusutil.h,v
retrieving revision 1.46
diff -c -p -r1.46 sidbusutil.h
*** include/sidbusutil.h	2001/03/01 19:18:07	1.46
--- include/sidbusutil.h	2001/03/27 23:20:57
*************** namespace sidutil
*** 269,274 ****
--- 269,275 ----
        }
      ~mux_passthrough_bus() {}
      void switch_bus() { index ^= 1; target = t[index]; }
+     void select_bus (int i) { index = (i != 0); target = t[index]; }
      
      // Some macros to make manufacturing of the cartesian-product
      // calls simpler.