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    SubjectRe: [PATCH] libata-sff: fix 32-bit PIO regression
    Sergei Shtylyov writes:
    > Hello.
    >
    > Hugh Dickins wrote:
    >
    > >> Commit 871af1210f13966ab911ed2166e4ab2ce775b99d (libata: Add 32bit PIO support)
    > >> caused all kind of errors on the ATAPI devices, so it's been empirically proven
    > >> that one shouldn't read/write an extra data word when a device isn't expecting
    > >> it already. "Don't do it then"; however still taking a chance to use 32-bit I/O
    > >> one last time when there are exactly 3 trailing bytes. Oh, and stop pointless
    > >> swapping bytes to and fro as well by using io*_rep() which shouldn't byte-swap.
    > >>
    > >> This should fix the kernel.org bug #12609.
    > >>
    > >> ---
    > >> This is hopefully better replacement for Hugh Dickins most recent patch
    > >> (http://marc.info/?l=linux-ide&m=123352294619281)...
    > >>
    > >
    > > Yes, looks nice, and works for me. My only criticism would be,
    > > minor issue unchanged by your patch, that actually "slop" isn't
    > > unlikely enough to deserve an "unlikely" - slop of 1 or 3 is
    > > unlikely, but slop of 2 is quite common.
    > >
    >
    > I guess that's the case only for the ATAPI devices, so I'm going to
    > keep it.

    I really don't think it's a good idea to play micro-optimisation
    unlikely() tricks when the likelihood depends on what kind of device
    the driver is talking to. In this case unlikely() is clearly wrong.


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