Messages in this thread | | | From | Arnd Bergmann <> | Subject | Re: [PATCH] Introduce CONFIG_VIRT_TO_BUS | Date | Thu, 24 May 2007 23:38:45 +0200 |
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On Wednesday 23 May 2007, Al Viro wrote: > > On Wed, May 23, 2007 at 05:01:55PM +1000, Stephen Rothwell wrote: > > Make some offending drivers depend on it and set > > CONFIG_ARCH_NO_VIRT_TO_BUS for ppc64 so that we don't build those drivers. > > Seeing how few targets _do_ have that, I'd invert the that. I.e. have > HAS_VIRT_TO_BUS in arch/*/Kconfig for the few architectures that have > that stuff.
Currently, that would mark x86_64 as HAS_VIRT_TO_BUS, while 64 bit powerpc would be NO_VIRT_TO_BUS. I think they really should be the same, probably like the other 64 bit targets, which means:
* If CONFIG_IOMMU is disabled, provide a __deprecated inline function that maps virt_to_bus to virt_to_phys, and allow building drivers that use it.
* If we build with CONFIG_IOMMU enabled, but don't support disabling the iommu, have no declaration for virt_to_bus at all, and disable the users in Kconfig
* If the usage of the iommu is determined at run time, warn about users of virt_to_bus at run time if it is enabled.
It could look like this
/* mm/memory.c or somewhere */ #if defined(CONFIG_HAS_VIRT_TO_BUS) && defined(CONFIG_IOMMU) unsigned long virt_to_bus(void *virt) { WARN_ON(iommu_enabled); return __virt_to_bus(virt); } #endif
/* include/linux/io.h */
#ifndef __virt_to_bus #define __virt_to_bus virt_to_phys /* some architectures need their own __virt_to_bus */ #endif
#ifdef CONFIG_HAS_VIRT_TO_BUS #ifdef CONFIG_IOMMU extern __deprecated unsigned long virt_to_bus(void *); #else static inline __deprecated unsigned long virt_to_bus(void *virt) { return __virt_to_bus(virt); } #endif #endif
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