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    SubjectRe: SCSI over USB showstopper bug?
    Jens Axboe <jens.axboe@oracle.com> wrote:

    > > > > it looks as if SG_GET_RESERVED_SIZE & SG_SET_RESERVED_SIZE
    > > > > are not in interaction with the underlying SCSI transport.
    > > > >
    > > > > Programs like readcd and cdda2wav that try to get very large SCSI
    > > > > transfer buffers get a confirmation for nearly any SCSI transfer size
    > > > > but later when readcd/cdda2wav try to transfer data with an
    > > > > actual SCSI command, they fail with ENOMEM.
    > > > >
    > > > > Correct fix: let sg.c make a callback to the underlying SCSI transport
    > > > > and let it get a confirmation tfor the buffer size.
    > > > >
    > > > > Quick and dirty fix: reduce the maximum allowed DMA size to the smallest
    > > > > max DMA size of all SCSI transports.
    > > >
    > > > real good fix:
    > > >
    > > > use SG_IO on the device directly that checks this already
    > >
    > > From looking into the source, this claim seems to be wrong.
    >
    > The block layer SG_IO entry point does what Arjan describes - it checks
    > the queue settings, which must match the hardware limits. It needs to,
    > since it won't accept a command larger than what the path to that device
    > will allow in one go. The SCSI sg variant may be more restricted, since
    > it should handle partial completions of such commands.

    Then someone should change the source to match this statements.

    From a report I have from the k3b Author, readcd and cdda2wav only work
    if you add a "ts=128k" option.

    Jörg

    --
    EMail:joerg@schily.isdn.cs.tu-berlin.de (home) Jörg Schilling D-13353 Berlin
    js@cs.tu-berlin.de (uni)
    schilling@fokus.fraunhofer.de (work) Blog: http://schily.blogspot.com/
    URL: http://cdrecord.berlios.de/old/private/ ftp://ftp.berlios.de/pub/schily
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