From mboxrd@z Thu Jan 1 00:00:00 1970 From: Lars-Peter Clausen Subject: Re: [PATCH] drivers: Let several drivers depends on HAS_IOMEM for 'devm_ioremap_resource' Date: Thu, 17 Jul 2014 12:40:25 +0200 Message-ID: <53C7A819.40403@metafoo.de> References: <201407130545.23004.marex@denx.de> <53C53CE1.4090803@gmail.com> <53C7269E.4010702@gmail.com> <6823014.2plXDE9VA9@wuerfel> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <6823014.2plXDE9VA9@wuerfel> Sender: linux-iio-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Arnd Bergmann , Chen Gang Cc: Guenter Roeck , Richard Weinberger , Greg Kroah-Hartman , dmitry.torokhov-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, linux-iio-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Benjamin Herrenschmidt , teg-B22kvLQNl6c@public.gmane.org, Thierry Reding , Lennox Wu , Marek Vasut , Liqin Chen , msalter-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, linux-pwm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, devel-gWbeCf7V1WCQmaza687I9mD2FQJk+8+b@public.gmane.org, linux-watchdog-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-input-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, "linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , knaack.h-Mmb7MZpHnFY@public.gmane.org, Martin Schwidefsky , Mischa.Jonker-HKixBCOQz3hWk0Htik3J/w@public.gmane.org, jic23-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, Geert Uytterhoeven List-Id: linux-input@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.