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From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>, <linux-kernel@vger.kernel.org>
Subject: Re: [RFC] I/O Access Abstractions
Date: Tue, 3 Jul 2001 00:08:48 +0200
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In-Reply-To: <E15HA1D-0006W0-00@the-village.bc.nu>
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>> > Last time I checked, ioremap didn't work for inb() and outb().
>> 
>> It should :)
>
>it doesnt need to.
>
>pci_find_device returns the io address and can return a cookie, ditto 
>isapnp etc

Yes, but doing that require 2 annoying things:

 - Parsing of this cookie on each inx/outx access, which can
take a bit of time (typically looking up the host bridge)

 - On machines with PIO mapped in CPU mem space and several
(or large) IO regions, they must all be mapped all the time,
which is a waste of kernel virtual space.

Why not, at least for 2.5, define a kind of pioremap that
would be the equivalent of ioremap for PIO ?

In fact, I'd rather have all this abstracted in a

ioremap_resource(struct resource *, int flags)
iounmap_resource(struct resource *)

("flags" is just an idea that could be used to pass things
like specific caching attributes, or whatever makes sense to
a given arch).

The distinction between inx/oux & readx/writex would still
make sense at least for x86.

Ben.


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