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

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Date:	Sun, 20 Jul 2014 17:45:40 +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>,
	Martin Schwidefsky <schwidefsky@...ibm.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 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 <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.
>
 
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.
> 
> 

Thanks.
-- 
Chen Gang

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