Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756283AbaGQL2v (ORCPT ); Thu, 17 Jul 2014 07:28:51 -0400 Received: from mail-pd0-f177.google.com ([209.85.192.177]:60074 "EHLO mail-pd0-f177.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754657AbaGQL2q (ORCPT ); Thu, 17 Jul 2014 07:28:46 -0400 Message-ID: <53C7B365.4080000@gmail.com> Date: Thu, 17 Jul 2014 19:28:37 +0800 From: Chen Gang User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.6.0 MIME-Version: 1.0 To: Arnd Bergmann , Lars-Peter Clausen 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 , cmetcalf@tilera.com Subject: Re: [PATCH] drivers: Let several drivers depends on HAS_IOMEM for 'devm_ioremap_resource' References: <201407130545.23004.marex@denx.de> <6823014.2plXDE9VA9@wuerfel> <53C7A819.40403@metafoo.de> <6485666.LVFO2YCEQx@wuerfel> In-Reply-To: <6485666.LVFO2YCEQx@wuerfel> Content-Type: text/plain; charset=ISO-8859-1 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 06:48 PM, Arnd Bergmann wrote: > On Thursday 17 July 2014 12:40:25 Lars-Peter Clausen wrote: >> 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' > > Ok, I see. > >> 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. > > 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. > According to current source code, tile still has chance to choose NO_IOMEM, for me, welcome the tile's maintainer's ideas or suggestions. Thanks. -- Chen Gang Open, share, and attitude like air, water, and life which God blessed -- 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/