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    SubjectRe: MMIO and gcc re-ordering issue
    Trent Piepho wrote:
    > Is there an issue with anything _besides_ coherent DMA?
    >
    > Could one have a special version of the accessors for drivers that
    > want to assume they are strictly ordered vs coherent DMA memory?
    > That would be much easier to get right, without slowing _everything_
    > down.

    It's better to be safe by default and then optimize the fast paths than
    to be relaxed by default and hang the machine in some piece of code that
    runs once a month. "Premature optimization is the root of all evil",
    and what not.

    > One could even go as far as to allow a driver to "#define
    > WANT_STRICT_IO" and then it would get the strict versions. Add that
    > to any driver that uses DMA and then worry about vetting those
    > drivers.

    See above -- if you must have a #define, then it should be WANT_RELAXED_IO.

    -Scott



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