Messages in this thread Patch in this message | | | Date | Fri, 25 May 2007 09:36:31 -0700 | From | "Dan Williams" <> | Subject | Re: [patch] Introduce CONFIG_HAS_DMA. |
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[ apologies for reviving an old conversation ]
On 2/26/07, Heiko Carstens <heiko.carstens@de.ibm.com> wrote: > From: Heiko Carstens <heiko.carstens@de.ibm.com> > > Architectures that don't support DMA can say so by adding a > config NO_DMA to their Kconfig file. This will prevent compilation > of some dma specific driver code. Also dma-mapping-broken.h isn't > needed anymore on at least s390. > This avoids compilation and linking of otherwise dead/broken code. >
I went back and read the thread leading up to this patch and I am of the opinion that John's approach (adding more stubs to dma-mapping-broken.h: http://marc.info/?l=linux-kernel&m=117219377712232&w=2) is needed in _addition_ to this Kconfig option. In my particular case I have an API with a DMA and a non-DMA path written in such a way that the DMA path can be compiled away. Without dma-mapping-broken.h support the API is unnecessarily forced to violate point 2 of Documentation/SubmittingPatches (#ifdefs are ugly).
In other words let CONFIG_HAS_DMA prevent pure DMA code from being built, but do not preclude "clever" implementations from calling broken code.
If there are no objections I plan to resubmit John's changes with the addition below, which allows CONFIG_HAS_DMA=n architectures to delete their respective dma-mapping.h file.
diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h index 9a663c6..2dc21cb 100644 --- a/include/linux/dma-mapping.h +++ b/include/linux/dma-mapping.h @@ -31,7 +31,11 @@ static inline int valid_dma_direction(int dma_direction) (dma_direction == DMA_FROM_DEVICE)); }
+#ifdef CONFIG_HAS_DMA #include <asm/dma-mapping.h> +#else +#include <asm-generic/dma-mapping-broken.h> +#endif
/* Backwards compat, remove in 2.7.x */ #define dma_sync_single dma_sync_single_for_cpu - 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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