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Date:      Sat, 05 Sep 2009 08:42:25 +0300
From:      Alexander Motin <mav@FreeBSD.org>
To:        Matthew Dillon <dillon@apollo.backplane.com>
Cc:        Ryan Rogers <webmaster@doghouserepair.com>, current@freebsd.org
Subject:   Re: non aligned DMA transfer attempted
Message-ID:  <4AA1FA41.1030804@FreeBSD.org>
In-Reply-To: <200909042314.n84NEMAS072077@apollo.backplane.com>
References:  <h7p0a3$k3m$1@FreeBSD.cs.nctu.edu.tw> <4AA03346.5010608@FreeBSD.org> <200909032210.n83MA67F059073@apollo.backplane.com> <A1B223C6-7291-4F86-B8AC-4EB5EF12F409@samsco.org> <200909042314.n84NEMAS072077@apollo.backplane.com>

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Matthew Dillon wrote:
> :>    The physio code directly maps the userland buffer via vmapbuf() and
> :>    supplies it as a BIO to the device.  The ATA driver does not use
> :>    BUSDMA (and never has)... it assumes BIOs are minimally aligned.
> :
> :Wrong.
> 
>     By the way Scott, do you honestly believe that idiotic one-line
>     answers just as a means to try to screw over my postings are
>     appropriate for someone of your standing in the FreeBSD community?

His answer is short, but correct, because all ATA drivers do use BUSDMA.
And as I have already said, BUSDMA manages proper alignment there, by
implementing bounce buffers.

-- 
Alexander Motin



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