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

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Message-ID: <53C7B7AF.3070103@gmail.com>
Date:	Thu, 17 Jul 2014 19:46:55 +0800
From:	Chen Gang <gang.chen.5i5j@...il.com>
To:	Arnd Bergmann <arnd@...db.de>
CC:	Guenter Roeck <linux@...ck-us.net>,
	Richard Weinberger <richard@....at>,
	Lars-Peter Clausen <lars@...afoo.de>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	dmitry.torokhov@...il.com, linux-iio@...r.kernel.org,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>, teg@...m.no,
	Thierry Reding <thierry.reding@...il.com>,
	Lennox Wu <lennox.wu@...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>,
	jic23@...nel.org, Geert Uytterhoeven <geert@...ux-m68k.org>,
	Liqin Chen <liqin.linux@...il.com>,
	Lennox Wu <lennox.wu@...il.com>
Subject: Re: [PATCH] drivers: Let several drivers depends on HAS_IOMEM for
 'devm_ioremap_resource'



On 07/17/2014 06:38 PM, Arnd Bergmann wrote:
> On Thursday 17 July 2014 17:29:31 Chen Gang wrote:
>>>
>>> COMPILE_TEST is a great tool in general, but it has its limits.
>>> In particular, the case for !CONFIG_IOMEM is completely obscure
>>> and we won't find any bugs by allowing more drivers to be built
>>> in those configurations, but attempting to do it would cause
>>> endless churn by changing each instance of 'depends on HAS_IOMEM'
>>> to 'depends on HAS_IOMEM || COMPILE_TEST'.
>>>
>>
>> Architecture members and driver members really have different tastes,
>> they are different roles. It really need additional discussion.
>>
>> For me, I only want to change devm_io*map*, not touch so much.
> 
> But what do you gain from that? All drivers that need these
> functions should already 'depends on HAS_IOMEM' and if they don't,
> we should fix /that/ instead. I don't see this dependency as any
> different from a lot of others (PCI, DMAENGINE, HAVE_CLK, ...)
> that we use to intentionally annotate drivers that need a particular
> feature to be present for compilation. Do you want to do the
> same hack to those?
> 
>> Welcome any other members' idea or suggestions.
> 
>>> Note that s390 no has gained support for IOMEM, tile has it most
>>> of the time (when PCI is enabled, so you get it in half the
>>> test builds already), score should set HAS_IOMEM and doesn't
>>> even have public compilers, and uml doesn't even compile in
>>> latest mainline. Nothing else ever sets NO_IOMEM.
>>>
>>

I guess, we are just discussing about them in another threads, so I skip
them. If it is still necessary to reply (e.g. I misunderstand), please
let me know, thanks.

>> In latest gcc and binutils, can compile score cross compiler
>> successfully for building kernel (but I am not quite sure whether the
>> compiling result are really OK, but I guess so).
> 
> Ok. Would you mind sending a patch that enables HAS_IOMEM on
> score?
>  

For me, welcome the score related maintainers' idea and suggestions.

>> And next (maybe after finish allmodconfig for microblaze), I shall try
>> to let uml pass allmodconfig for linux-next tree.
> 
> That is a fair goal, but it seems better to do that by ensuring
> we don't build any code that tries to call the MMIO functions
> rather than trying to make them build.
> 

When I am performing uml, I will try and also communicate with the
related maintainers for it (their suggestions and ideas are valuable).

Thanks.
-- 
Chen Gang

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