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    SubjectRe: [PATCH 02/10] ide-tape: use single continuous buffer
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    Hi,

    On Wed, Mar 25, 2009 at 5:13 PM, Tejun Heo <tj@kernel.org> wrote:
    > Hello, Grant.
    >
    > Grant Grundler wrote:
    >> On Wed, Mar 25, 2009 at 7:17 AM, Tejun Heo <tj@kernel.org> wrote:
    >>> Impact: simpler buffer allocation and handling, fix DMA transfers
    >> ...
    >>> +               atomic_set(&bh->b_count, bcount);
    >>>                if (atomic_read(&bh->b_count) == bh->b_size)
    >> ...
    >>
    >> I'm failing to see why bh->b_count is an atomic_t.
    >> I always assumed tapes were exclusive access devices
    >> and would be serialized at a higher level.
    >
    > Beats me.  I don't know.  The code is generally pretty over-engineered
    > but, well, it's an ancient piece of code with (probably too) rich
    > history.

    Yep, actually the driver was even bigger and it implemented a bunch of fun stuff
    like command pipelining and those atomics had to protect the pipeline from
    simultaneous ->open()s through its chrdev interface, IIRC.

    --
    Regards/Gruss,
    Boris
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