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    SubjectRe: [PATCH v3 1/2] virtio-scsi: first version
    On 12/19/2011 01:22 PM, Hannes Reinecke wrote:
    >> + case VIRTIO_SCSI_S_UNDERRUN:
    >> + set_host_byte(sc, DID_ERROR);
    >> + break;
    > Hmm. Not sure this is correct.
    > UNDERRUN could be a valid state, eg it is quite common to send
    > an INQUIRY with a length of 255 bytes. And only evaluate the
    > bytes which are actually send back.

    This happens when you send an INQUIRY with a sglist of 255 bytes and an
    ALLOCATION LENGTH of 300 bytes. The spec says "VIRTIO_SCSI_S_UNDERRUN
    [is returned] if the content of the CDB requires transferring more data
    than is available in the data buffers".

    > And, it's not good style to match the same DID_XXX error code to
    > several internal errors. I would prefer having a 1:1 match for
    > VIRTIO_SCSI_S_XXX and DID_XXX error codes.

    There is no DID_XXX value for underrun, but it's quite useful to have it
    diagnosed separately in traces.

    >> +static struct scsi_host_template virtscsi_host_template = {
    >> + .module = THIS_MODULE,
    >> + .name = "Virtio SCSI HBA",
    >> + .proc_name = "virtio_scsi",
    >> + .queuecommand = virtscsi_queuecommand,
    >> + .this_id = -1,
    >> +
    >> + .can_queue = 1024,
    >> + .dma_boundary = UINT_MAX,
    >> + .use_clustering = ENABLE_CLUSTERING,
    >> +};
    >> +
    > Hmm. Apparently you support more than one LUN, yet no
    > ->slave_alloc() callback is present. So how do you scan the bus here?

    What does slave_alloc have to do with scanning? I don't need hostdata,
    so I don't have slave_alloc.

    Scanning is here:

    err = scsi_add_host(shost, &vdev->dev);
    if (err)
    goto scsi_add_host_failed;

    scsi_scan_host(shost);

    > Do you actually have a working backend implementation?

    Hmm... yes, of course...

    Paolo


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