Re: [PATCH] dma-debug: disable DMA_API_DEBUG for now

Arnd Bergmann
2009-06-05T14:58:26Z

On Friday 05 June 2009, FUJITA Tomonori wrote:
> I think that the better fix can handle both cases per device:
>
> - multiple identical dma addresses should not happen (with devices
> behind hardware IOMMU)
> - multiple identical dma addresses could happen

I guess you could also have the case where for a given range
of addresses, you use a linear mapping and the dma addresses
can be identical, while for other physical addresses you would
rely on address translation.

For example on PowerPC/Cell with infiniband adapters, you can get
linear mapping behavior for DMA_ATTR_WEAK_ORDERING but IOMMU
translation without that flag, for the same device and same
physical address.