From: Linus Torvalds <torvalds@osdl.org>
To: Deepak Saxena <dsaxena@plexity.net>
Cc: Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: Being more anal about iospace accesses..
Date: Wed, 15 Sep 2004 15:46:29 -0700 (PDT) [thread overview]
Message-ID: <Pine.LNX.4.58.0409151540260.2333@ppc970.osdl.org> (raw)
In-Reply-To: <20040915222157.GA17284@plexity.net>
On Wed, 15 Sep 2004, Deepak Saxena wrote:
>
> Since we are on the subject of io-access, I would like a
> clarification/opinion on the read*/write* & in*/out* accessors
> (and now the ioread/write equivalents). Are these functions only meant
> to be used for PCI memory-mapped devices or _any_ memory mapped devices?
It really depends on the bus architecture.
At some point, if the bus is different enough from a "normal" setup, you
should just use your own accessor functions. Trying to overload
"readl/writel" is just too painful.
However, at that point you should also realize that you can't re-use _any_
of the existing chip drivers, and you'll have to write your own. If the
bus is exotic enough, that's not a problem, and you'd have to do that
anyway. But there really aren't all that many "exotic" buses around any
more.
Quite frankly, of your two suggested interfaces, I would select neither.
I'd just say that if your bus is special enough, just write your own
drivers, and use
cookie = ixp4xx_iomap(dev, xx);
...
ixp4xx_iowrite(val, cookie + offset);
which is perfectly valid. You don't have to make these devices even _look_
like a PCI device. Why should you?
Linus
next prev parent reply other threads:[~2004-09-15 22:48 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <Pine.LNX.4.58.0409081543320.5912@ppc970.osdl.org>
[not found] ` <Pine.LNX.4.58.0409150737260.2333@ppc970.osdl.org>
2004-09-15 16:30 ` Being more anal about iospace accesses Linus Torvalds
2004-09-15 16:54 ` Jörn Engel
2004-09-15 17:07 ` Linus Torvalds
2004-09-15 17:32 ` Jörn Engel
2004-09-15 17:57 ` Linus Torvalds
2004-09-15 18:06 ` Linus Torvalds
2004-09-15 19:34 ` Greg KH
2004-09-15 19:53 ` Linus Torvalds
2004-09-15 20:06 ` Greg KH
2004-09-16 14:58 ` Horst von Brand
2004-09-15 17:45 ` Nikita Danilov
2004-09-15 18:09 ` Linus Torvalds
2004-09-15 18:40 ` Chris Wedgwood
2004-09-15 17:07 ` Jeff Garzik
2004-09-15 17:16 ` Roland Dreier
2004-09-15 17:39 ` Linus Torvalds
2004-09-15 20:07 ` Russell King
2004-09-15 17:36 ` Horst von Brand
2004-09-15 17:40 ` Brian Gerst
2004-09-15 16:56 ` Dave Jones
2004-09-15 17:19 ` Roger Luethi
2004-09-15 17:23 ` Richard B. Johnson
2004-09-15 22:21 ` Deepak Saxena
2004-09-15 22:46 ` Linus Torvalds [this message]
2004-09-15 23:09 ` Deepak Saxena
2004-09-16 12:51 ` Geert Uytterhoeven
2004-09-16 22:10 ` Deepak Saxena
2004-09-15 22:29 ` Roland Dreier
2004-09-15 23:26 ` Being more careful " Linus Torvalds
2004-09-16 0:10 ` viro
2004-09-16 11:40 ` David Woodhouse
2004-09-16 12:25 ` David Woodhouse
2004-09-16 14:01 ` Linus Torvalds
2004-09-18 9:46 ` Kai Henningsen
2004-09-15 18:25 Being more anal " linux
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