Currently for block devices both the SCSI_IOCTL_GET_IDLUN and 
SCSI_IOCTL_GET_BUS_NUMBER ioctls yield the value 0 (type: int).

Various applications that utilize the sg driver use these ioctls
to work out the relationship between sg devices and their higher
level counterparts in the sd, sr, st and osst drivers. Examples
that spring to mind are cdrecord, cdparanoia, SANE and sg_utils.

This has been discussed in an earlier threaded started by me:
http://marc.theaimsgroup.com/?l=linux-scsi&m=103967899608891&w=2
in which my patch removed the ioctls in question from the block
level. This broke non-scsi block devices that used applications
that thought they were talking to an sg device **.

The attachment fine tunes the original patch: for scsi block
devices (i.e. owned by the sd or sr drivers) these 2 ioctls
are redirected to the scsi mid level; for non-scsi block
devices they will yield the value as 0 as they do now in
lk 2.5.53 .


** This "yield 0" strategy will come unstuck when 2 or more
cd writers (for example) are connected to the same box.
Hence to be well formed, these ioctls (together) should
produce unique tuples for each device (be they ATA(PI) or
SCSI).