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Subject: Re: PCI drivers - memory mapped vs. I/O ports
To: EdV@macrolink.com (Ed Vance)
Date: Mon, 18 Mar 2002 20:32:09 +0000 (GMT)
Cc: linux-kernel@vger.kernel.org ('linux-kernel')
In-Reply-To: <11E89240C407D311958800A0C9ACF7D13A7715@EXCHANGE> from "Ed Vance" at Mar 18, 2002 11:50:41 AM
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From: Alan Cox <alan@lxorguk.ukuu.org.uk>
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> If a PCI device can be programmed equally well via I/O port space or memory
> space, what are the reasons to chose one space over the other when writing
> the driver?

mmio is posted on a PC i/o ports are not. That means you have to be more
careful but also means that

	write
	write
	write
	read

is a lot faster

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