linux-kernel - Re: [RFC/PATCH] iomap: Add specific address space _

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Date:	Mon, 18 Feb 2008 15:28:24 +1100
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <greg@...ah.com>,
	Al Viro <viro@....linux.org.uk>, jgarzik@...ox.com,
	David Miller <davem@...emloft.net>,
	David Howells <dhowells@...hat.com>, miles@....org
Subject: Re: [RFC/PATCH] iomap: Add specific address space __iomap for
	iomap pointers


On Mon, 2008-02-18 at 14:35 +1100, Benjamin Herrenschmidt wrote:
> The current iomap stuff (pci_iomap, ioport_map, pcim_iomap, ...) is
> confusing as it returns pointers in the _miomem address space.
> 
> However, even if that would work on some architectures, the result
> of those functions is -not- to be used as an __iomem, with accessors
> such as readl/writel, but only with the new brand of specific accessors
> (ioread32/iowrite32/...).

Willy and Al raised a good point off-list, is that in all effective
implementations of this, the MMIO case -does- use compatible virtual
addresses with ioremap, in fact even powerpc does.

Thus if we consider iomap as a kind of superset of the ioremap space
with a "hole" in it for PIO, it's fine to use the same address space
marker and it's fine to interchange the accessors when one -knows-
for sure it's dealing with memory and not IO.

Thus drop my patch,

Ben.


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