On Sat, 22 Nov 2008 22:10:05 -0800
"Yu, Fenghua" <fenghua.yu@xxxxxxxxx> wrote:
> >Hmm, intel_dma_mapping_error is used to test only the value that
> >intel_map_single() returns. If intel_map_single() returns a non-zero
> >dma address, it belongs to hwdev's domain. So intel_dma_mapping_error
> >can simply return 1 (failure) if the dma_addr is zero.
>
> Then there is no usage of hwdev which is one of two parameters in intel_dma_mapping_error?
Yes, and that's how VT-d dma_mapping_error() works on X86_64.
Note that we use hwdev in the following way, see
arch/x86/kernel/include/asm/dma-mapping.h
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
}
dma_mapping_error uses a point to struct device to choose a proper
dma_mapping_ops.
> Maybe checking dma_addr only is good enough for the function? At least it's fast to check errors.
Yeah, that's what my patch does (and what x86 VT-d dma_mapping_error()
does).
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