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    On Fri, 6 Jul 2001, David S. Miller wrote:

    > What about for drivers of SAC-only devices, they eat the overhead
    > when highmem is enabled too?

    Yes. It's not an unreasonable overhead considering that it's configured
    out for all the non-highmem kernels that will be shipped. Keep in mind
    that the expected lifespan for 32 bit systems is now less than 3 years, so
    elaborate planning that delays implementation buys us nothing more than a
    smaller window of usefulness.


    > This says nothing about the real reason the IA64 solution is
    > unacceptable, the inputs to the mapping functions which must
    > be "page+offset+len" triplets as there is no logical "virtual
    > address" to pass into the mapping routines on 32-bit systems.

    On x86 a 64 bit DMA address cookie is fine. If you've got concerns, tell
    us what you have in mind for a design.


    > Face it, the ia64 stuff is not what we can use across the board. It
    > simply doesn't deal with all the necessary issues. Therefore,
    > encouraging driver author's to use this ia64 hacked up scheme is
    > not such a hot idea until we have a real API implemented.

    So what's the API?

    -ben

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