Did you try the ioctls for SCSI generic :
http://sg.danny.cz/sg/p/sg_v3_ho.html#ioctl ?
SCSI_IOCTL_GET_IDLUN, SG_GET_SCSI_ID should do the trick.
I did not use any SCSI HW in the last years though, and I hope the documentation is still valid for current kernels. I don't see any reason to have changed the ioctls though.