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    SubjectRe: kmalloc
    Alan Cox wrote:
    >
    > > alan@lxorguk.ukuu.org.uk (Alan Cox) writes:
    > >
    > > |> > Is kmalloc guaranteed to alloc a physically contigous buffer? My exact
    > > |>
    > > |> Yes
    > >
    > > No. It is only contiguous in the kernel virtual space.
    >
    > Thats vmalloc. If you have an architecture where kmalloc blocks are
    > not linear to the I/O devices you'll have a very bad time making anything
    > work

    Call me nuts, but it _really_ bothers me that experienced kernel
    developers can have disagreements about basic stuff. I blame the lack
    of documentation. Where's vmalloc (and kmalloc) explained? I couldn't
    find anything in the source.

    Add to that Alan's mistake this morning about phys_to_virt() etc. and I
    think we have a clear pattern: these people aren't dummies, so we can't
    blame them, there just isn't adequate documentation.

    This is going to bite us more and more as the developer pool gets
    bigger.

    I'm not flaming anyone (especially someone of Alan's stature), this kind
    of mistake is happening repeatedly and is being made by the best
    developers Linux can boast. I think we _have_ to recognise the
    shortfalls in the current system. Undocumented source-code is fine if
    you're sure people can find documentation somewhere...

    Figuring out how to use a routine by looking at other code that uses it
    is a BAD idea, but it's the path of least resistance (and the path to
    bugs).

    To summarise: good developers have some wrong ideas about some of the
    basic building blocks of the kernel, and it's not fair to blame
    individuals. This needs fixing.

    Comments?

    Neil
    ps: if ever the FUD merchants needed ammo, incidents like these are
    perfect.
    pps: i'm quite sure MS suffer from similar problems, but let's not copy
    'em.

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