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Re: ISA

To: "Geert Uytterhoeven" <geert@linux-m68k.org>
Subject: Re: ISA
From: "Bradley D. LaRonde" <brad@ltc.com>
Date: Wed, 2 Jan 2002 09:36:44 -0500
Cc: "Jun Sun" <jsun@mvista.com>, "Jim Paris" <jim@jtan.com>, "Alan Cox" <alan@lxorguk.ukuu.org.uk>, "Maciej W. Rozycki" <macro@ds2.pg.gda.pl>, "Linux/MIPS Development" <linux-mips@oss.sgi.com>
References: <Pine.GSO.4.21.0201021040260.1574-100000@vervain.sonytel.be>
Sender: owner-linux-mips@oss.sgi.com
----- Original Message -----
From: "Geert Uytterhoeven" <geert@linux-m68k.org>
To: "Bradley D. LaRonde" <brad@ltc.com>
Cc: "Jun Sun" <jsun@mvista.com>; "Jim Paris" <jim@jtan.com>; "Alan Cox"
<alan@lxorguk.ukuu.org.uk>; "Maciej W. Rozycki" <macro@ds2.pg.gda.pl>;
"Linux/MIPS Development" <linux-mips@oss.sgi.com>
Sent: Wednesday, January 02, 2002 4:41 AM
Subject: Re: ISA


> On Tue, 1 Jan 2002, Bradley D. LaRonde wrote:
> > ----- Original Message -----
> > From: "Jun Sun" <jsun@mvista.com>
> > To: "Jim Paris" <jim@jtan.com>
> > Cc: "Alan Cox" <alan@lxorguk.ukuu.org.uk>; "Geert Uytterhoeven"
> > <Geert.Uytterhoeven@sonycom.com>; "Maciej W. Rozycki"
<macro@ds2.pg.gda.pl>;
> > "Linux/MIPS Development" <linux-mips@oss.sgi.com>
> > Sent: Tuesday, January 01, 2002 2:22 PM
> > Subject: Re: ISA
> >
> >
> > > 1. each address space has an id.
> > > 2. kernel pre-defines a couple of well-known ones, 0 for CPU physical,
> > >    1 for virtual, etc.
> > > 3. When drivers discover the devices, they get the address and also
> > >    the address space id where the address resides.
> > > 4. there are a set of macro's that converts/maps an address or an
> > >    address region from one space to another.
> >
> > The first thing that jumps out at me is that now every bus access has an
> > added switch in it.
> >
> > Either that or drivers would get back access function pointers, but that
> > eliminates the chance to inline trivial bus accesses.
>
> Not completely. ioremap() and friends can handle the address space ID and
> return an appropriate pointer. That pointer can still be handled by
readl() and
> friends.

Yup.  I forgot about having to run all bus addresses through ioremap.

Regards,
Brad


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