Messages in this thread | | | Date | Wed, 27 May 2009 12:58:46 +0900 | Subject | Re: [PATCH] asm-generic: add a dma-mapping.h file | From | FUJITA Tomonori <> |
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On Tue, 26 May 2009 13:35:41 +0100 Arnd Bergmann <arnd@arndb.de> wrote:
> On Tuesday 26 May 2009, FUJITA Tomonori wrote: > > > dma_get_cache_alignment() is still less generic than > > > the other functions, as this is still architecture > > > specific. Should I leave that out as well then? > > > > Yes, I think that only adding generic functions is a better > > approach. Overriding with #ifdef is really ugly. > > > > Ok, will do. > > [trimming Cc list a bit, as the subject has changed] > > Could you be more specific as to why you think the #ifdef > in this file is ugly? I agree that we should always avoid > #ifdef in a device driver file or around the usage of an > API, but we use it everywhere when defining an optional
Seems that people think regard #ifdef in *.c bad, I think.
> API, e.g. > > #ifdef CONFIG_DMA_API_DEBUG > extern void dma_debug_add_bus(struct bus_type *bus); > #else > static inline void dma_debug_add_bus(struct bus_type *bus) > { > { > #endif
This example is inappropriate; a different way to use #ifdef.
This just ensures that dma_debug_add_bus() is available even if CONFIG_DMA_API_DEBUG is disabled.
It's completely different from a way how you use #ifdef.
> #ifndef clear_user_highpage > static inline void clear_user_highpage(struct page *page, unsigned long vaddr) > { > void *addr = kmap_atomic(page, KM_USER0); > clear_user_page(addr, vaddr, page); > kunmap_atomic(addr, KM_USER0); > } > #endif
#define clear_user_highpage(page,vaddr) \ __cpu_clear_user_highpage(page, vaddr)
Personally, I don't fancy this style but it's a matter of taste, I guess.
> This has always made a lot of sense to me when you are defining > something that you want to become a No-op in certain configurations > or that only needs special handling in a few cases. IIRC, Linus > has stated that he prefers the second of the two styles above when > you have the choice, which is why I started out that way, while > for the dma_debug stuff, the CONFIG_ symbol clearly makes sense. > > Arnd <>< > -- > 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/
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