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Date:	Sun, 20 Jul 2014 17:45:40 +0800
From:	Chen Gang <>
To:	Lennox Wu <>
CC:	Richard Weinberger <>, Arnd Bergmann <>,
	Lars-Peter Clausen <>,
	Guenter Roeck <>,
	Greg Kroah-Hartman <>,
	Dmitry Torokhov <>,,
	Benjamin Herrenschmidt <>,
	Tom Gundersen <>,
	Thierry Reding <>,
	Marek Vasut <>,
	Liqin Chen <>,,,,,,
	"" <>,, Martin Schwidefsky <>,
	Martin Schwidefsky <>,,
	Geert Uytterhoeven <>,,
Subject: Re: [PATCH] drivers: Let several drivers depends on HAS_IOMEM for

On 07/20/2014 04:38 PM, Chen Gang wrote:
> On 07/19/2014 02:02 AM, Chen Gang wrote:
>>> 2014-07-18 18:51 GMT+08:00 Richard Weinberger <>:
>>>> Am 18.07.2014 12:44, schrieb Chen Gang:
>>>>> On 07/18/2014 03:35 PM, Richard Weinberger wrote:
>>>>>> Am 18.07.2014 02:36, schrieb Chen Gang:
>>>>>>> On 07/18/2014 02:09 AM, Richard Weinberger wrote:
>>>>>>>> Am 17.07.2014 12:48, schrieb Arnd Bergmann:
>>>>>>>>> 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.
>>>>>>>> If UML is the only arch without io memory the dependency on !UML seems
>>>>>>>> reasonable to me. :-)
>>>>>>> For me, if only uml left, I suggest to implement dummy functions within
>>>>>>> uml instead of let CONFIG_UML appear in generic include directory. And
>>>>>>> then remove all HAS_IOMEM and NO_IOMEM from kernel.
>>>>>> Erm, this is something completely different.
>>>>>> I thought we're focusing on COMPILE_TEST?
>>>>> COMPILE_TEST is none-architecture specific, but UML is. So in generic
>>>>> include folder, if we're focusing on choosing whether COMPILE_TEST or
>>>>> UML, for me, I will choose COMPILE_TEST.
>>>>> If we're not only focusing on COMPILE_TEST, for me, if something only
>>>>> depend on one architecture, I'd like to put them under "arch/*/" folder.
>>>>> Especially, after that, we can remove all HAS_IOMEM and NO_IOMEM, nobody
>>>>> has to think of them again. :-)
>>>> And then we end up with a solution that on UML a lot of completely useless
>>>> drivers are build which fail in various interesting manners because you'll
>>>> add stubs for all kinds of io memory related functions to arch/um/?
>>>> We had this kind of discussion already. You'll need more than ioremap...
>>>> I like Arnd's idea *much* more to make COMPILE_TEST depend on !UML.
>> That will let UML itself against COMPILE_TEST (but all the other
>> architectures not).
>> And if let COMPILE_TEST depend on !UML, can we still remove all
>> HAS_IOMEM and NO_IOMEM from kernel? (I guess so).
>> If we can remove them, we can send related patch firstly -- that will
>> let current discussion be in UML architecture wide instead of kernel
>> wide.
> Next, I shall:
>  - Remove HAS_IOMEM and NO_IOMEM from kernel, firstly.
>  - Try to make dummy IOMEM functions for score architecture.
>  - Continue discussing with UML for it.
Oh, sorry, I forgot, after remove IOMEM from kernel, also s390 and tile
need implement dummy IOMEM if !PCI.

If possible, I shall try to implement the dummy IOMEM in 'asm-generic',
and let uml, score, s390 and tile use them when they need.

> By the way: how about HAS_DMA? can we treat it as HAS_IOMEM (remove
> it from kernel)? (for me, I guess we can not).
> At present, I shall finish sending patch for removing IOMEM today, and
> continue to welcome any ideas, suggestions or completions for IOMEM or
> DMA.

Chen Gang

Open share and attitude like air water and life which God blessed
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