Re: [parisc-linux] [PATCH] Support for AD1889 PCI Soundchip

[Grant Grundler <grundler@parisc-linux.org>]

On Mon, Aug 22, 2005 at 01:03:34PM +0200, Takashi Iwai wrote:
> At Fri, 19 Aug 2005 19:36:55 -0600,
> Grant Grundler wrote:
> > 
> > On Fri, Aug 19, 2005 at 07:53:22PM +0200, Takashi Iwai wrote:
> > > Check his patch carefully.  It doesn't add any extra accesses (except
> > > for one readl to flush in irq handler - I guess it was added to be
> > > sure?).  The original driver didn't use these fields effectively at
> > > all, too.
> > 
> > Sorry - I didn't look at patch at all.
> > If the fields were never used, removing them is fine.
> > If they *could* have been used, then removing them is a bad idea.
> 
> They won't be used/referred any more at all, so why do you need still
> to keep them?

I don't - removing them is fine.

> > In general, referencing parameters in IO device registers is NOT
> > a good substitute for caching the values "locally" in host mem.
> 
> A cached value is not accurate, especially if you want to get a
> precise position.

Caching is only possible if the register is "constant" for
the duration of it's use. e.g. offset or "count down" registers
can't be cached.


>   The position callback should return the accurate
> position as much as possible since this can be used from the low
> latency calculation like dmix.

ok - no problem. That's reasonable.

grant


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