Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756687AbaGQKka (ORCPT ); Thu, 17 Jul 2014 06:40:30 -0400 Received: from smtp-out-155.synserver.de ([212.40.185.155]:1116 "EHLO smtp-out-155.synserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756009AbaGQKkZ (ORCPT ); Thu, 17 Jul 2014 06:40:25 -0400 X-SynServer-TrustedSrc: 1 X-SynServer-AuthUser: lars@metafoo.de X-SynServer-PPID: 17631 Message-ID: <53C7A819.40403@metafoo.de> Date: Thu, 17 Jul 2014 12:40:25 +0200 From: Lars-Peter Clausen User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Icedove/24.6.0 MIME-Version: 1.0 To: Arnd Bergmann , Chen Gang CC: Guenter Roeck , Richard Weinberger , Greg Kroah-Hartman , dmitry.torokhov@gmail.com, linux-iio@vger.kernel.org, Benjamin Herrenschmidt , teg@jklm.no, Thierry Reding , Lennox Wu , Marek Vasut , Liqin Chen , msalter@redhat.com, linux-pwm@vger.kernel.org, devel@driverdev.osuosl.org, linux-watchdog@vger.kernel.org, linux-input@vger.kernel.org, "linux-kernel@vger.kernel.org" , knaack.h@gmx.de, Martin Schwidefsky , Mischa.Jonker@synopsys.com, jic23@kernel.org, Geert Uytterhoeven Subject: Re: [PATCH] drivers: Let several drivers depends on HAS_IOMEM for 'devm_ioremap_resource' References: <201407130545.23004.marex@denx.de> <53C53CE1.4090803@gmail.com> <53C7269E.4010702@gmail.com> <6823014.2plXDE9VA9@wuerfel> In-Reply-To: <6823014.2plXDE9VA9@wuerfel> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/17/2014 11:20 AM, 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'. The point of this exercise is that we do not have to replace a good chunk of 'depends on COMPILE_TEST' with 'depends on COMPILE_TEST && HAS_IOMEM' E.g. the typical Kconfig entry for your random SoC peripheral driver looks like config ARCH_FOOBAR_DRIVER depends on ARCH_FOOBAR || COMPILE_TEST ... Now when COMPILE_TEST is not set there is a implicit dependency on HAS_IOMEM since the architecture will provide it. If COMPILE_TEST is selected the driver will also be build-able on architectures that do no have HAS_IOMEM and hence linking the driver fails. One way to fix this is of course to replace the COMPILE_TEST with (COMPILE_TEST && HAS_IOMEM). But this is very often overlooked and only noticed later on when somebody actually builds a allyesconfig on an architecture that does not provide HAS_IOMEM. To avoid these kinds of build errors and tedious fixup patches the idea is to provide a stub function when HAS_IOMEM is not enabled, but COMPILE_TEST is enabled. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/