On Wed, Nov 18, 2009 at 16:17, Øyvind Harboe <[email protected]> wrote:
>>> Actually, the minidrivers don't clone today, so that's already taken care 
>>> of.
>>
>> Doesn't that apply only to zy1000.c ?
>
> The USB case needs to delay execution to build a long
> scan, so there copy is required.

I think you misunderstood what I am proposing. I did not suggest to
execute the sequence immediately. I am not only aware of the USB
latency, in fact the arm11 code relies on it for the burst mode.

>>> The USB drivers have a 1ms roundtrip problem to contend with, the
>>> rest is in the noise, essentially. There is plenty of evidence to this 
>>> effect.
>>
>> *You* brought up performance as concern... My goal was primarily
>> streamlining code.
>
> I did. We need both streamlined and fast code. Until we have both sorted,
> we leave things the way they are.

My proposal does not imply any decrease in speed, it can lead to an
increase. It still builds up a jtag sequence before executing it, it
just modifies the interface for value types.

>> Your example seemed to be too much of a workaround rather than
>> addressing the problem directly, which IMO is that the uint32_t case
>> is so common that there should be a short unambiguous way to deal with
>> it.
>>
>> Of course even a set of standard wrappers to package the set-up of the
>> most common field configurations would help a lot, without also
>> serving as a shortcut into the minidriver-layer to avoid the copying.
>
> I've got some thoughts on how to do this, but nothing written up yet.
>
>>> Also we have to *carefully* consider how we can make *small* steps that
>>> can be tested on all the hardware combinations. Otherwise any change
>>> is unlikely to pay off. We're getting there but it will and should take 
>>> time.
>>
>> It was a suggestion on long-term goals. Small steps are usually most
>> effective when they go towards a specific target.
>
> I'm doing small steps in a branch for now. We'll see how it pans out.
>
> That branch might end up being a big leap before it is pushed to
> the master branch.

Michael
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