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    SubjectRe: [GIT PULL] SCSI queuecommand API change for 2.6.37-rc1
    On Fri, Nov 12, 2010 at 8:28 PM, Matthew Wilcox <matthew@wil.cx> wrote:
    > Actually, it'd be even better if we took away an argument.
    >
    > int queuecommand(struct scsi_cmnd *cmd);
    >
    > Every single driver sets cmd->scsi_done = done;

    .. and i that's all they really ever do with it, I guess that that
    would indeed be an improvement.

    I still do think that passing in shost is actually a good idea, since
    you'll normally be needing it for locking and other things anyway
    (looking at the libata-scsi.c one, for example, the very first thing
    it wants to do is to look up the port from the shost pointer).

    Having to inevitably do that silly double dereference
    ("cmd->device->host") seems bogus. Passing in the host you want to
    queue something on seems to be natural, and avoids that nasty chain of
    dereferences, so it really should improve the code.

    I don't think there are any drivers that don't want that host pointer
    pretty much immediately, even if they can elide the locking. But I
    admit I only looked at two (qla4xxx driver does the exact same thing:
    the very first thing in the queuecommand function is
    "to_qla_host(cmd->device->host)", but it wants that hostdata thing
    too, so whatever.)

    So the shost pointer is certainly a lot more useful than the 'done'
    function pointer. So yeah, I'd switch them around - pass the 'done'
    thing indirectly, and the shost directly.

    Linus


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