myhdl-list

[myhdl-list] Would you ...

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

use function attributes instead of named arguments for a MyHDL module 
configuration?  Not sure if this would be a good idea or not.

Example:

     def mymodule(clock, reset, a, b, c):

         if hasattr(mymodule, 'use_filter') and mymodule.use_filter:
	    aflt = Signal(intbv(0, min=c.min, max=c.max))
             gens = myfilter(clock, reset, a, aflt)
         else:
             aflt,gens = (a,[])

         @always_seq(clock.posedge, reset=reset)
         def hdl():
             c.next = a + b
         gens = [gens, hdl]

         return gens

Traditionally you would add:

     mymodule(clock, reset, a, b, c, UseFilt=False)


After writing this it dawned on me, most of the time it would be bad.  I 
guess a function attribute would only be useful if you wanted every 
MyHDL module instance to act exactly the same (e.g. if the filter was 
enabled in one instance it would be enabled in all instances).

So where this might be useful is if you are using technology primitives 
(FPGA primitives) and you want to instantiate a primitive based on a 
technology, say Xilin or Altera.  But in that case you would want the 
attribute to be global to all the modules, hmmm.

Regards,
Chris

Re: [myhdl-list] Would you ...

[Tom D. <td...@di...>]

My personal preference is named arguments.

I also use signal arguments to pass some functionality as well.

Such as:

mymodule(clock=None,reset=None, a=sig1, b=sig2, c=sig3, UseFilt=False)

Would make it asynchronous. The mymodule definition would have to check 
for clock==None and return the appropriate logic.




On 09/25/2012 10:45 AM, Christopher Felton wrote:
> use function attributes instead of named arguments for a MyHDL module
> configuration?  Not sure if this would be a good idea or not.
>
> Example:
>
>       def mymodule(clock, reset, a, b, c):
>
>           if hasattr(mymodule, 'use_filter') and mymodule.use_filter:
> 	    aflt = Signal(intbv(0, min=c.min, max=c.max))
>               gens = myfilter(clock, reset, a, aflt)
>           else:
>               aflt,gens = (a,[])
>
>           @always_seq(clock.posedge, reset=reset)
>           def hdl():
>               c.next = a + b
>           gens = [gens, hdl]
>
>           return gens
>
> Traditionally you would add:
>
>       mymodule(clock, reset, a, b, c, UseFilt=False)
>
>
> After writing this it dawned on me, most of the time it would be bad.  I
> guess a function attribute would only be useful if you wanted every
> MyHDL module instance to act exactly the same (e.g. if the filter was
> enabled in one instance it would be enabled in all instances).
>
> So where this might be useful is if you are using technology primitives
> (FPGA primitives) and you want to instantiate a primitive based on a
> technology, say Xilin or Altera.  But in that case you would want the
> attribute to be global to all the modules, hmmm.
>
> Regards,
> Chris
>
>
>
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Re: [myhdl-list] Would you ...

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

On 9/25/2012 10:56 AM, Tom Dillon wrote:
> My personal preference is named arguments.
>
> I also use signal arguments to pass some functionality as well.
>
> Such as:
>
> mymodule(clock=None,reset=None, a=sig1, b=sig2, c=sig3, UseFilt=False)
>
> Would make it asynchronous. The mymodule definition would have to check
> for clock==None and return the appropriate logic.
>
>

I agree, name arguments is what you usually want and your example is a 
perfect demonstration of creating very flexible IP.

The use of "interfaces" helps as well.

     mymodule(syssigs=None, datapath=datapath, UseFilt=False)

and in the module you can have

     def mymodule(...):
         (a,b,c) = datapath.GetSigs()
         if syssigs is not None:
             clock = syssigs.clock
             reset = syssigs.reset
             # ...
         else:
             # ...

where datapath is:
     class Datapath(object):
         def __init__(self):
             self.a,self.b,self.c = [Signal...]
         def GetSigs(self):
             return self.a,self.b,self.c


Regards,
Chris