linux-kernel - Re: [PATCH] drivers: Let several drivers depends on HAS_IOMEM for 'devm_ioremap

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Date:	Sun, 20 Jul 2014 17:56:32 +0800
From:	Chen Gang <gang.chen.5i5j@...il.com>
To:	Richard Weinberger <richard@....at>
CC:	Lennox Wu <lennox.wu@...il.com>, Arnd Bergmann <arnd@...db.de>,
	Lars-Peter Clausen <lars@...afoo.de>,
	Guenter Roeck <linux@...ck-us.net>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	linux-iio@...r.kernel.org,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Tom Gundersen <teg@...m.no>,
	Thierry Reding <thierry.reding@...il.com>,
	Marek Vasut <marex@...x.de>,
	Liqin Chen <liqin.linux@...il.com>, msalter@...hat.com,
	linux-pwm@...r.kernel.org, devel@...verdev.osuosl.org,
	linux-watchdog@...r.kernel.org, linux-input@...r.kernel.org,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	knaack.h@....de, Martin Schwidefsky <schwidefsky@...ibm.com>,
	Mischa.Jonker@...opsys.com, jic23@...nel.org,
	Geert Uytterhoeven <geert@...ux-m68k.org>, cmetcalf@...era.com,
	heiko.carstens@...ibm.com
Subject: Re: [PATCH] drivers: Let several drivers depends on HAS_IOMEM for
 'devm_ioremap_resource'

On 07/20/2014 05:51 PM, Chen Gang wrote:
> On 07/20/2014 05:45 PM, Richard Weinberger wrote:
>>
>>
>> Am 20.07.2014 10:38, schrieb Chen Gang:
>>> On 07/19/2014 02:02 AM, Chen Gang wrote:
>>>>> 2014-07-18 18:51 GMT+08:00 Richard Weinberger <richard@....at>:
>>>>>> 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.
>>
>> This needs to be last, otherwise lot's of stuff will break.
>>
> 
> OK, thanks, that sounds reasonable to me.
> 
>>>  - Try to make dummy IOMEM functions for score architecture.
>>>
>>>  - Continue discussing with UML for it.
>>
>> If you find sane dummy functions for both UML and score I'm fine with it.
>>
> 
> For me, what you said is necessary, tile and s390 also need dummy IOMEM
> when !PCI.
> 
> So for me, I shall implement them in "include/asm-generic", and let uml,
> score, tile and s390 use dummy IOMEM when they need.
> 
> Welcome any other members ideas, suggestions and completions.
> 
> 

And sorry, I can not finish this discussion and send patch for it within
this week, for it is really a long necessary discussion.

But, hope we can finish this discussion and send patch for it within
this month (but in current condition, I am not quite sure).

And after finish discussion, welcome any other members help sending
related patch for it (e.g. implement dummy IOMEM in "asm-generic",
remove all IOMEM in kernel wide).

Thanks.
-- 
Chen Gang

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