Re: [PATCH] scsi: Make scsi_vpd_lun_id() able to use T10 vendor ID based designators

[Paul Mackerras <paulus@ozlabs.org>]

On Wed, May 04, 2016 at 12:04:16PM +0200, Hannes Reinecke wrote:
> On 05/04/2016 08:58 AM, Paul Mackerras wrote:
> > This adds code to scsi_vpd_lun_id() to enable it to use T10 vendor ID
> > based designators.  This is needed to allow alua to work on disks that
> > don't have any designators of type 2, 3 or 8.  Commit 0047220c6c36
> > ("scsi_dh_alua: use unique device id", 2016-02-19) added a requirement
> > that alua can only be used on disks for which scsi_vpd_lun_id() can
> > produce an identifying string.
> > 
> > Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
> > ---
> >  drivers/scsi/scsi_lib.c |   14 ++++++++++++++
> >  1 file changed, 14 insertions(+)
> > 
> > diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
> > index 8106515..f4f69cc 100644
> > --- a/drivers/scsi/scsi_lib.c
> > +++ b/drivers/scsi/scsi_lib.c
> > @@ -3214,6 +3214,20 @@ int scsi_vpd_lun_id(struct scsi_device *sdev, char *id, size_t id_len)
> >  			goto next_desig;
> >  
> >  		switch (d[1] & 0xf) {
> > +		case 0x1:
> > +			/* T10 vendor ID */
> > +			if (cur_id_size > d[3])
> > +				break;
> > +			/* Prefer EUI-64 or NAA IEEE Registered Extended */
> > +			if ((cur_id_type == 0x2 || cur_id_type == 0x3) &&
> > +			    cur_id_size == d[3])
> > +				break;
> > +			cur_id_size = d[3];
> > +			cur_id_str = d + 4;
> > +			cur_id_type = d[1] & 0xf;
> > +			id_size = snprintf(id, id_len, "%*phN", cur_id_size,
> > +					   cur_id_str);
> > +			break;
> >  		case 0x2:
> >  			/* EUI-64 */
> >  			if (cur_id_size > d[3])
> > 
> Nearly.
> The thing is, a T-10 vendor specific ID is _supposed_ to be an ASCII
> string. So I'd rather have it decoded as such.

Do we need to defend against non-printing characters in the string?

> And we're missing decoding for 'vendor-specific' ID, too.

There's no guarantee that this would be ASCII, right?  So would you
print it in hex?

Also, is there a preference between these types?  For example, is an
8-byte EUI-64 preferable to a vendor-specific ID of any length?

Cheers,
Paul.