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    SubjectRe: Serverworks OSB4 in impossible state
    Am Mon, 2002-06-10 um 18.41 schrieb Daniela Engert:

    > The intersting bits of the DMA status register are bits 0 though 2. A
    > value of 5 indicates the condition "interrupt from unit, DMA state
    > machine active". This is a valid status! It basically means the unit
    > issued an interrupt before the PRD table is exhausted. This makes sense
    > because the CD-ROM units fails to transfer the amount of data described
    > by the PRD table because of the non-recoverable read error.

    Shouldn't the error bit be set too? (But that wouldn't make any
    difference with the current driver ...)

    > What you makes sense (the next DMA transfer is scheduled but never
    > carried out by the CD-ROM unit) except for the panic, ofcoz. The
    > correct driver action in this case were stopping the DMA engine and
    > issuing a reset of the state machines involved (both on the host and
    > the unit side).

    The message, the comments in the code, and what Alan wrote here:
    suggest that trying to recover from this condition is extremely
    dangerous (note that the kernel doesn't even panic(), because
    a sync() may kill a disk, the comments say).

    Anyway, thanks a lot for your insightful comments.

    Martin Wilck Phone: +49 5251 8 15113
    Fujitsu Siemens Computers Fax: +49 5251 8 20409
    Heinz-Nixdorf-Ring 1
    D-33106 Paderborn

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