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Date: Wed, 7 Jul 2004 16:17:27 -0600 (MDT)
From: Scott Long <scottl@freebsd.org>
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To: Poul-Henning Kamp <phk@phk.freebsd.dk>
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cc: ticso@cicely.de
cc: "Charles M. Hannum" <mycroft@netbsd.org>
cc: FreeBSD current users <current@freebsd.org>
cc: Julian Elischer <julian@elischer.org>
Subject: Re: speeding up ugen by an order of magnitude. 
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On Wed, 7 Jul 2004, Poul-Henning Kamp wrote:
> In message <200407072129.15095.mycroft@netbsd.org>, "Charles M. Hannum" w=
rites:
> >On Wednesday 07 July 2004 20:46, Charles M. Hannum wrote:
> >> 1) You'll need to add an interface for assigning pipes for read and wr=
ite,
> >> since there may be more than just bulk pipes (and may be more than one=
 bulk
> >> pipe in each direction), and we only have have device node to work wit=
h.
> >
> >Seems I misspoke there.  That part looks fine.
> >
> >I think you're going to be screwed by the buffer alignment, though.  Thi=
s also
> >causes some issues with umass if you're not using a bounce buffer.
>
> We've already had that issue with ATA for the b=F8rked Geode controller:
> physio does nothing for alignment and relies on userland doing something
> sensible.
>
> I think this is pretty reasonable for the kind of hardware-near
> work that physio is usually employed in (including if we use it for
> ugen).
>
> Obviously, if the alignment is not OK, EINVAL should be returned,
> and that means that the driver should explicitly check the alignment.

Note that busdma can handle alignment now for loaded buffers by using
bounce pages.

Scott