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SubjectRe: [PATCH v3] Fix dma_mapping_error for 32bit x86
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On Sat, 29 Nov 2008 13:46:27 +0100 (CET)
Thomas Bogendoerfer <tsbogend@alpha.franken.de> wrote:

> Devices like b44 ethernet can't dma from addresses above 1GB. The driver
> handles this cases by falling back to GFP_DMA allocation. But for detecting
> the problem it needs to get an indication from dma_mapping_error.
> The bug is triggered by using a VMSPLIT option of 2G/2G.
>
> Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
> ---
>
>
> diff -ru orig/linux-2.6.27.4/include/asm-x86/dma-mapping.h linux-2.6.27.4/include/asm-x86/dma-mapping.h
> --- orig/linux-2.6.27.4/include/asm-x86/dma-mapping.h 2008-10-26 00:05:07.000000000 +0200
> +++ linux-2.6.27.4/include/asm-x86/dma-mapping.h 2008-10-26 11:06:14.000000000 +0100
> @@ -74,15 +74,13 @@
> /* Make sure we keep the same behaviour */
> static inline int dma_mapping_error(struct device *dev, dma_addr_t dma_addr)
> {
> -#ifdef CONFIG_X86_32
> - return 0;
> -#else
> +#ifdef CONFIG_X86_64
> struct dma_mapping_ops *ops = get_dma_ops(dev);
> if (ops->mapping_error)
> return ops->mapping_error(dev, dma_addr);
>
> - return (dma_addr == bad_dma_address);
> #endif
> + return (dma_addr == bad_dma_address);
> }

Surely, 2.6.27.4 needs this fix (and all the stable trees need this
too, I think).

This can't be cleanly applied to the current git (dma-mapping.h was
moved). How about just removing the ifdef? I think that it's clean a
bit.


diff --git a/arch/x86/include/asm/dma-mapping.h b/arch/x86/include/asm/dma-mapping.h
index 7f225a4..dc22c07 100644
--- a/arch/x86/include/asm/dma-mapping.h
+++ b/arch/x86/include/asm/dma-mapping.h
@@ -71,15 +71,11 @@ static inline struct dma_mapping_ops *get_dma_ops(struct device *dev)
/* Make sure we keep the same behaviour */
static inline int dma_mapping_error(struct device *dev, dma_addr_t dma_addr)
{
-#ifdef CONFIG_X86_32
- return 0;
-#else
struct dma_mapping_ops *ops = get_dma_ops(dev);
if (ops->mapping_error)
return ops->mapping_error(dev, dma_addr);

return (dma_addr == bad_dma_address);
-#endif
}

#define dma_alloc_noncoherent(d, s, h, f) dma_alloc_coherent(d, s, h, f)

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