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

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Message-ID: <53CB801D.1030603@gmail.com>
Date:	Sun, 20 Jul 2014 16:38:53 +0800
From:	Chen Gang <gang.chen.5i5j@...il.com>
To:	Lennox Wu <lennox.wu@...il.com>
CC:	Richard Weinberger <richard@....at>, 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>
Subject: Re: [PATCH] drivers: Let several drivers depends on HAS_IOMEM for
 'devm_ioremap_resource'

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.

 - Try to make dummy IOMEM functions for score architecture.

 - Continue discussing with UML for it.


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.


Thanks.
-- 
Chen Gang

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