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Date:      Mon, 21 Jul 1997 19:01:59 +0200 (MET DST)
From:      Luigi Rizzo <luigi@labinfo.iet.unipi.it>
To:        msmith@atrad.adelaide.edu.au (Michael Smith)
Cc:        hasty@rah.star-gate.com, hackers@FreeBSD.ORG, multimedia@FreeBSD.ORG
Subject:   Re: auto dma?
Message-ID:  <199707211701.TAA21422@labinfo.iet.unipi.it>
In-Reply-To: <199707211744.DAA24577@genesis.atrad.adelaide.edu.au> from "Michael Smith" at Jul 22, 97 03:14:25 am

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> Amancio Hasty stands accused of saying:
> > 
> > luigi@labinfo.iet.unipi.it said:
> > > I am looking at Mike's idea of using DMA_AUTOMODE and a circular
> > > buffer, but unfortunately there are no support routines to read the
...
> > Does anyone know how to read the current number of bytes transferred in 
> > in a dma transfer? 

the intel data sheet for the i82371 (also known as PIIX), a PCI chipset
which implements a number of standard isa devices including timer and
dma controller, is available at the intel site (www.intel.com).

Although it probably is not exactly the same as the original 8237, it
myght still give some ideas on what to do. The main problem with old
peripherals is that they often did not allow a safe reading of 16-bit
registers such as counters, which can be incremented while you read the
two pieces. I don't know if this affected the original 8237, but sure
was a problem with some old PC timer.

Apart from this, I'd look in the PIIX data sheet.

Finally, if someone is familiar with Linux or NetBSD kernel
(specifically for the isa routines) let me know.

	Cheers
	Luigi
-----------------------------+--------------------------------------
Luigi Rizzo                  |  Dip. di Ingegneria dell'Informazione
email: luigi@iet.unipi.it    |  Universita' di Pisa
tel: +39-50-568533           |  via Diotisalvi 2, 56126 PISA (Italy)
fax: +39-50-568522           |  http://www.iet.unipi.it/~luigi/
_____________________________|______________________________________



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