linux-kernel - Re: [patch] x86, voyager: fix ioremap

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Message-Id: <20080427.154620.177583216.davem@davemloft.net>
Date:	Sun, 27 Apr 2008 15:46:20 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	jeff@...zik.org
Cc:	James.Bottomley@...senPartnership.com, mingo@...e.hu,
	tglx@...utronix.de, linux-kernel@...r.kernel.org, hpa@...or.com,
	torvalds@...ux-foundation.org
Subject: Re: [patch] x86, voyager: fix ioremap_nocache()

From: Jeff Garzik <jeff@...zik.org>
Date: Sun, 27 Apr 2008 18:39:24 -0400

> I disagree with this semantics change.  A number of code places _and 
> drivers_ GET IT RIGHT, and these are all broken now?

[ Note, James's patch that you quoted is about mapping DMA
  memory, in dma_declare_coherent_memory(), rather than devices.
  But I know what you are trying to talk about Jeff. :-) ]

Wrt. ioremap() semanics, it is important to realize that if
the implementation of this on x86 has been giving non-cached
I/O mappings out up until recently, you can expect that there
are hundreds of drivers that might now be broken.

That's the sad fact of the ubiquity of x86, and it doesn't matter how
we defined the API is some document.

Anyways, my point is that this angle should be strongly considered in
any discussion about ioremap() behavior.

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