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

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Message-ID: <53C796E1.8080708@nod.at>
Date:	Thu, 17 Jul 2014 11:26:57 +0200
From:	Richard Weinberger <richard@....at>
To:	Arnd Bergmann <arnd@...db.de>, Chen Gang <gang.chen.5i5j@...il.com>
CC:	Guenter Roeck <linux@...ck-us.net>,
	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>,
	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'

Am 17.07.2014 11:20, schrieb Arnd Bergmann:
> On Thursday 17 July 2014 09:27:58 Chen Gang wrote:
>>                                          gfp_t gfp_mask, unsigned int order);
>>  extern void devm_free_pages(struct device *dev, unsigned long addr);
>>  
>> +#ifdef CONFIG_HAS_IOMEM
>>  void __iomem *devm_ioremap_resource(struct device *dev, struct resource *res);
>> +#elif defined(CONFIG_COMPILE_TEST)
>> +static inline void __iomem *devm_ioremap_resource(struct device *dev,
>> +                                               struct resource *res)
>> +{
>> +       pr_warn("no hardware io memory, only for COMPILE_TEST\n");
>> +       return (__force void __iomem *)ERR_PTR(-ENXIO);
>> +}
>> +#endif /* CONFIG_HAS_IOMEM || CONFIG_COMPILE_TEST */
>>  
>>  /* allows to add/remove a custom action to devres stack */
> 
> To be honest, I think it's a bad idea to introduce wrappers functions
> that are only available when CONFIG_COMPILE_TEST is set.
> 
> 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'.
> 
> 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.

Huh? UML (v3.16-rc5-143-gb6603fe) builds fine here. What build issue are you facing?

Thanks,
//richard
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