I know this is an ancient post , but the changer will be accessed by an 'sg' device , ie scsi generic. If you are running Linux , it will already have sg support.
sg provides a lower level interface to SCSI devices than st. st is for scsi tapes.
you need to install the mtx
command line tool as well to control the media changer device.
sg devices for the tape drives will be created as well
system messages will show the devices , with a type '1' being a tape device , a type '8' being a media changer , a type '0' being a disk ...
see sg2 , is type 8 and it's a 'ch' ....
[ 6.145348] st 2:0:0:0: Attached scsi generic sg0 type 1
[ 6.145449] st 4:0:0:0: Attached scsi generic sg1 type 1
[ 6.145542] ch 4:0:0:1: Attached scsi generic sg2 type 8
[ 6.145696] st 5:0:0:0: Attached scsi generic sg3 type 1
[ 6.146526] st 6:0:0:0: Attached scsi generic sg4 type 1
[ 43.891764] scsi 7:0:0:0: Attached scsi generic sg5 type 0
[ 43.898283] scsi 7:0:1:0: Attached scsi generic sg6 type 0
[ 43.908209] sd 7:0:2:0: Attached scsi generic sg7 type 0
[ 43.918352] sd 7:0:3:0: Attached scsi generic sg8 type 0
[ 43.930734] sd 7:1:0:0: Attached scsi generic sg9 type 0