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

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Date:	Thu, 17 Jul 2014 11:51:19 +0200
From:	Thierry Reding <thierry.reding@...il.com>
To:	Chen Gang <gang.chen.5i5j@...il.com>
Cc:	Arnd Bergmann <arnd@...db.de>, 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,
	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'

On Thu, Jul 17, 2014 at 05:29:31PM +0800, Chen Gang wrote:
> 
> 
> On 07/17/2014 05:20 PM, Arnd Bergmann wrote:
> > 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'.
> >
> 
> 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.
> 
> 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.
> > 
> 
> 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).

I was only able to ever build a partial bare-metal toolchain for score.
There's no uClibc, glibc or newlib support, so it becomes rather useless
as a Linux architecture.

Also when I run the cross-compiler on a score defconfig build, I get a
bunch of these:

	score-unknown-elf-gcc-4.9.0: internal compiler error: Segmentation fault (program as)

Thierry

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