Re: [myhdl-list] [RFC/PATCH] constant driver support

[Christopher F. <chr...@gm...>]

On 9/10/11 9:05 AM, Sébastien Bourdeauducq wrote:
> Hi,
>
> the patch below implements constant driver support. A constant driver
> generator yields None.
>
> * Generic waiter object: block on None clauses
> * New InfiniteWaiter object
> * inferWaiter: create InfiniteWaiter when generator yields None
> * always_comb decorator: yield None on empty sensitivity list
> * conversion/analyze: return empty sensitivity list for generators that
> yield None
> * Verilog/VHDL conversion: wait forever on empty sensitivity list
>
<snip code patch>

I haven't had time to review your code, so I don't have any specific 
feedback on the code but a couple general comments.

Jan Decaluwe created a page outlining the process to contribute changes, 
http://www.myhdl.org/doku.php/dev:patches.  Have a look at this page, it 
is very useful.  You might want to create an hg bundle, in addition, to 
expedite any patches that might be accepted.

If I recall, from the conversation it sounded like constant drivers are 
supported but not from a generator.  Something like this works, currently:

   def testc(y):
       x = Signal(intbv(5)[8:])
       @always_comb
       def rtl():
           y.next = x

       return rtl


The above will generate a constant driver (e.g. assign x = 5 in 
Verilog).  But your patch proposes an alternative method to create 
constant drivers, correct?

Your proposed changes would support something like:

   def testc(y):
       @always_comb
       def rtl():
           y.next = 5

       return rtl

My question would be: Are there any error cases that might be missed now 
(that were previously caught)?


Regards,
Chris Felton