[ECOS] HAL_DELAY_US()

[Øyvind Harboe]

On 8/14/06, Gary Thomas <gary@mlbassoc.com> wrote:
> Øyvind Harboe wrote:
> > Going through my changes to eCos, I ran into HAL_DELAY_US().
> >
> > Does this function belong in the application or eCos?
> >
> > If it can be implemented in a correct manner that does not require any
> > configuration, then I believe it belongs in the HAL.
> >
> > If it needs to be tuned to the hardware in question, then I believe it
> > belongs in the application space.
> >
> > The implementation in EB40a is busted because it is not
> > multithreading/interrupt safe.
> >
> >
> > Ref. earlier discussions HAL_DELAY_US() should take *at least* that
> > many us, there is no upper limit or requirement on precision as such.
>
> IMO, HAL_DELAY_US() should not be used if interrupts or thread switches
> can cause a perturbation.  It's *only* function is to provide very simple
> timing when devices require it.  It should not be used for arbitrary delays,
> certainly not in user/application code.  For that, use 'cyg_thread_delay()'

Agreed.

However, e.g. i2c bitbang relies on it and I do believe that a
consensus was reached to make it compulsory.

IMO, a HAL should have no implementation or a correct implementation.

EB40a has a broken implementation and that implementation should be
deleted or replaced.

-- 
Øyvind Harboe
http://www.zylin.com

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