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From: ali@xcf.berkeley.edu
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Date: 4 Dec 1997 04:46:07 -0000
Message-ID: <19971204044607.7535.qmail@xcf.berkeley.edu>
To: freebsd-hackers@freebsd.org
Subject: DMA to isa bus.
Sender: owner-freebsd-hackers@freebsd.org
X-Loop: FreeBSD.org
Precedence: bulk

Hi. I'm running freebsd 2.2.2-release.

isa.c has, in isa_dmastart():

		/* If B_RAW flag is set, then use autoinitialise mode */
		if (flags & B_RAW) {
		  if (flags & B_READ)
			outb(DMA1_MODE, DMA37MD_AUTO|DMA37MD_WRITE|chan);
		  else
			outb(DMA1_MODE, DMA37MD_AUTO|DMA37MD_READ|chan);
		}
		else
		if (flags & B_READ)
			outb(DMA1_MODE, DMA37MD_SINGLE|DMA37MD_WRITE|chan);
		else
			outb(DMA1_MODE, DMA37MD_SINGLE|DMA37MD_READ|chan);
		outb(DMA1_FFC, 0);


>From the #defins in i8237.h, _AUTO is single with auto initialize. So
my choices are basically single or single with auto. I would like to
use demand mode or block mode instead. Is there a good reason why these
modes aren't supported? How should I go about initiating a demand or
block mode transfer?

Thanks.
  Ali.