> it is now recognized as follow :
>
> cd0 at scsibus0 target 3 lun 0: <TOSHIBA, CD-ROM XM-3401TA, 1534> SCSI2
> 5/cdrom
> removable
> cd0: async, 8-bit transfers
>
> but it wont talk to me : neither mount nor dd  succeed to use it ...
> Any thoughts ?

ahem ...  Hate to reply to myself, especially in this circumstances .
In fact the previous fix (adding an entry in the quirk table) works ...
I just forgot to check that there was a CD in the drive ! Stupid me !!!
With a CD properly inserted, mount is happy ...

This is what I changed (I suppose all the revision of this marvelous drive
have the
same symptoms ...)

Index: scsiconf.c
===================================================================
RCS file: /pub/NetBSD-CVS/syssrc/sys/dev/scsipi/scsiconf.c,v
retrieving revision 1.179
diff -r1.179 scsiconf.c
482c482
<        "TOSHIBA ","CD-ROM XM-3401TA",  "0283"},
PQUIRK_CDROM|PQUIRK_NOLUNS},
---
>        "TOSHIBA ","CD-ROM XM-3401TA",  ""}, PQUIRK_CDROM|PQUIRK_NOLUNS},