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SubjectRe: IB: Add DMA mapping functions to allow device drivers to interpose
On Wed, 13 Dec 2006 12:11:27 -0800
Ralph Campbell <ralph.campbell@qlogic.com> wrote:

> > I'd have picked this up if it had been in git-infiniband for even a couple
> > of days. I'm assuming this all got slammed into mainline because of the
> > merge window thing.
> >
> > I cannot find these patches on the kernel mailing list. I cannot find the
> > pull request anywhere.
> >
> > > +static inline u64 ib_dma_map_single(struct ib_device *dev,
> > > + void *cpu_addr, size_t size,
> > > + enum dma_data_direction direction)
> >
> > no, dma_map_single() returns a dma_addr_t.
>
> ib_dma_map_single() allows the ib_ipath device driver to interpose
> on IOMMU allocations and not do them by returning the kernel
> virtual address as the "DMA address". I started with dma_addr_t
> but it was pointed out to me that sparc64 defines dma_addr_t
> as u32. This would cause addresses to be truncated.
> Also, I chose u64 because the return value from ib_dma_*() is
> stored in the ib_sge.addr field which is u64.
>
> My preference would be to change the offending uses of dma_addr_t
> to u64. Do you have a better solution?

We should be able to use dma_addr_t for this? Is it not the case that the
values we're dealing with here _are_ DMA addresses? I think a more complete
description of the problem we're trying to solve here would help.

I'm not sure what the problem is with sparc64 - perhaps its dma_addr_t
really is a "cookie" and isn't a physical bus address? But you want a value
which is really a physical bus address? Dunno.

Perhaps dma64_addr_t can be used here.
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