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From: Ken Wong <kwong@fathergoose.net6c.io.org>
Message-Id: <199508250734.DAA01286@fathergoose.net6c.io.org>
Subject: Re: How to abort a DMA transfer ?
To: luigi@labinfo.iet.unipi.it (Luigi Rizzo)
Date: Fri, 25 Aug 1995 03:34:29 -0400 (EDT)
Cc: freebsd-hackers@FreeBSD.org
In-Reply-To: <199508201701.TAA12803@labinfo.iet.unipi.it> from "Luigi Rizzo" at Aug 20, 95 07:01:00 pm
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Luigi Rizzo Wrote:
> 
> How (within a device driver) do I abort a DMA transfer which has
> been started but has not completed yet ? I am having this problem
> in the driver for a hand-scanner (the scanner does some read ahead;
> meanwhile, a user might close the device and we want to abort the
> transfer and free the buffer). I am surprised I haven't seen (or
> understood!) anything like this in existing drivers, not even in
> the floppy driver!

To abort the DMA transfer:

1) reset the device that is using the DMA. being that scanner controller.

2) change some DMA registers for that channel. ( I don't have my book 
   here today, but I can find out if needed).

Ken