Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!wuarchive!gem.mps.ohio-state.edu!tut.cis.ohio-state.edu!ucsd!rutgers!texbell!attctc!chasm
From: chasm@attctc.Dallas.TX.US (Charles Marslett)
Newsgroups: comp.sys.ibm.pc
Subject: Re: DMA transfer
Summary: Don't let DOS in on it!
Keywords: comp.sys.ibmpc
Message-ID: <9577@attctc.Dallas.TX.US>
Date: 5 Oct 89 02:39:05 GMT
References: <JGROVER.891002160902@MAINE.MAINE.EDU>
Organization: The Unix(R) Connection, Dallas, Texas
Lines: 32

In article <JGROVER.891002160902@MAINE.MAINE.EDU>, JGROVER@MAINE writes:
> I'd appreciate tapping into the cumulative knowledge out there concerning
> the proper methods for doing DMA from a peripheral board. I need to know
> how to set up the channel  for both reads and writes. I know how to get
> my board to do the read or write once the channel is set.
> 
> John Grover

After a long series of hassles with MSDOS and its demented attitude toward
device drivers, I would strongly reccommend you avoid writing a device
driver and making your access to the device "clean."

It hurts to say that (I have even implemented IBM's bisync protocol as a
Unix line discipline, so I have properly encapsulated I/O tasks in the past).

MSDOS just does not understand any kind of block device that is not part of
the file system!  Otherwise, either put the DMA on the board (I think this is
called first-party-DMA), or plan to learn about all the idiosynchracies of
the 8237 and those of the almost compatible C&T, WD, etc., motherboard
chip sets.

May you live in interesting times (;^).

Charles
> University of Maine Computing Center


===========================================================================
Charles Marslett
STB Systems, Inc.  <== Apply all standard disclaimers
Wordmark Systems   <== No disclaimers required -- that's just me
chasm@attctc.dallas.tx.us