Re: [PATCH] SCSI: detect missing data for INQUIRY

[James Bottomley <James.Bottomley@HansenPartnership.com>]

On Mon, 2008-10-27 at 13:00 -0400, Alan Stern wrote:
> On Mon, 27 Oct 2008, James Bottomley wrote:
> 
> > > --- usb-2.6.orig/drivers/scsi/scsi_scan.c
> > > +++ usb-2.6/drivers/scsi/scsi_scan.c
> > > @@ -602,6 +602,13 @@ static int scsi_probe_lun(struct scsi_de
> > >  				    (sshdr.ascq == 0))
> > >  					continue;
> > >  			}
> > > +		} else {
> > > +			/*
> > > +			 * Additional Length and Vendor fields missing
> > > +			 * probably means nothing was transferred.  Try again.
> > > +			 */
> > > +			if (inq_result[4] == 0 && inq_result[8] == 0)
> > > +				continue;
> > 
> > Really, no.
> > 
> > A legitimate minimal response from a device is zero in the additional
> > length field.  If it does that, then the vendor field is bound to be
> > zero as well.
> > 
> > About the best we can do is check the first four fields.  For them to be
> > all zero, it would have to be a minimal response SCSI-1 device (RDF of
> > zero) ... hopefully they're all dead by now.
> 
> Then you're saying that the patch should everything up to
> inq_result[8]?  Or maybe even beyond?  I can do that.  Would that be 
> acceptable?

No ... "first four fields" means everything up to inq_result[3].
Anything beyond that would be legitimately zero if they were.

James