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Date:	Fri, 18 Jul 2014 08:26:59 +0800
From:	Chen Gang <>
To:	Arnd Bergmann <>, Chris Metcalf <>
CC:	Lars-Peter Clausen <>,
	Guenter Roeck <>,
	Richard Weinberger <>,
	Greg Kroah-Hartman <>,,,
	Benjamin Herrenschmidt <>,,
	Thierry Reding <>,
	Lennox Wu <>, Marek Vasut <>,
	Liqin Chen <>,,,,,,
	"" <>,, Martin Schwidefsky <>,,,
	Geert Uytterhoeven <>
Subject: Re: [PATCH] drivers: Let several drivers depends on HAS_IOMEM for

On 07/18/2014 05:05 AM, Arnd Bergmann wrote:
> On Thursday 17 July 2014 16:41:14 Chris Metcalf wrote:
>> On 7/17/2014 7:28 AM, Chen Gang wrote:
>>> On 07/17/2014 06:48 PM, Arnd Bergmann wrote:
>>>> AFAICT, NO_IOMEM only has a real purpose on UML these days. Could we take
>>>> a shortcut here and make COMPILE_TEST depend on !UML? Getting random stuff
>>>> to build on UML seems pointless to me and we special-case it in a number of
>>>> places already.
>>> According to current source code, tile still has chance to choose
>>> NO_IOMEM, for me, welcome the tile's maintainer's ideas or suggestions.
>> I'm not really sure.  It's true that on tile, if you don't enable PCI
>> support there's no other I/O memory (or I/O port) space you can use.
>> We pretty much always enable PCI support in our kernel, though.  I'm
>> kind of surprised that other architectures don't also have the model
>> that IOMEM requires PCI, but perhaps most architectures just don't
>> encode that in the Kconfig file?
> Only s390 as far as I know. Most architectures have integrated
> peripherals that use MMIO without PCI.
>> My observation is just that if I remove the "NO_IOMEM if !PCI" from
>> arch/tile/Kconfig, my build fails with ioremap() undefined.  No doubt I
>> could work around that, but my assumption was that NO_IOMEM was exactly the
>> right thing to express the fact that without PCI there is no I/O memory 
> Your assumption is correct.
> For tile by itself it would certainly be best to leave this
> dependency, it makes no sense to enable IOMEM without PCI.
> That doesn't solve the problem of COMPILE_TEST enabling drivers
> that require IOMEM though. An easy hack for that would be to
> make COMPILE_TEST depend on HAS_IOMEM, but it gets into hacky territory
> there, and it's not clear if this is any better than the original patch
> to provide fallbacks for ioremap and friends. Definitely simpler
> though.

OK, thank all of you, tile just likes most of architectures to support
IOMEM, and at present, we can focus score and uml only.

Chen Gang

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