Re: [PARPORT] Re: Parport & DMA -- patch-2.2.7-tmw3

Bert De Jonghe (
Thu, 13 May 1999 19:38:15 +0200 (CEST)

On Wed, 12 May 1999, Philip Blundell wrote:

> Tim Waugh wrote:
> >On Wed, 12 May 1999, Bert De Jonghe wrote:
> >
> >> Maybe parport_pc can have a private DMA-capable buffer (private_data
> >> ?) allocated if DMA is configured ? The cost would be an extra copy
> >> of the data into this buffer, but for me that's a price I'm willing to
> >> pay to avoid making the high-level drivers more complex and putting PC
> >> artifacts all over the place.
> >
> >I'd rather not take the extra copy for no reason.
> Actually, this is quite a good suggestion.

Thank you ;-)

> The low-level driver can inspect the address of the buffer it's handed,
> see if it's suitable for DMA as it stands (ie on an ISA machine, make
> sure it is entirely below the 16MB limit) and either use it directly or
> copy it to a bounce buffer as necessary.

Aha, another obvious improvement ... (Tim, I'll add such a check to that
patch I sent you & make a new one on monday -- I'm out of the office for
some days and can't test things over here)

> So yes, you will get an extra copy some of the time, but it might be
> worth it to save on software complexity. The time to copy probably
> isn't that big a deal.

I also think that this time to copy is ignoreable.

Kind regards !


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This archive was generated by hypermail 2.0b3 on Thu 13 May 1999 - 13:39:48 EDT