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Date: Fri, 04 Sep 2009 00:21:10 +0300
From: Alexander Motin <mav@FreeBSD.org>
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To: Ryan Rogers <webmaster@doghouserepair.com>, current@FreeBSD.org
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Subject: Re: non aligned DMA transfer attempted
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Ryan Rogers wrote:
> I'm having a bit of a problem getting my DVD drive(s) to work correctly. 
>   I'm trying to transfer my DVD collection to my media server, but 
> whenever I run vobcopy, /var/log/messages gets spammed with:
> 
> acd0: FAILURE - non aligned DMA transfer attempted
> acd0: setting up DMA failed
> 
> I added a bit more information to the first message to see if I could 
> figure out what was actually going on.  request->data was 0xd40e0c37, 
> ch->dma.alignment was 2, and request->bytecount was 2048.

Actually I don't understand what for this check was made there. It is 
busdma infrastructure business to implement buffer bouncing to manage 
requested alignment. But this check enforces application level to bother 
with this. Usually it works fine, as memory often allocated aligned. But 
probably here is some specifics in your application. Could you try to 
just to comment-out that request->data check?

-- 
Alexander Motin