I just happened to be reading the following a few hours before seeing your
question:
http://sunsite.unc.edu/mdw/HOWTO/CD-Writing-HOWTO-4.html#ss4.6
4.6 "How to probe for SCSI-devices after boot?"
The file drivers/scsi/scsi.c contains the information
/*
* Usage: echo "scsi add-single-device 0 1 2 3" >/proc/scsi/scsi
* with "0 1 2 3" replaced by your "Host Channel Id Lun".
* Consider this feature BETA.
* CAUTION: This is not for hotplugging your peripherals. As
* SCSI was not designed for this you could damage your
* hardware !
* However perhaps it is legal to switch on an
* already connected device. It is perhaps not
* guaranteed this device doesn't corrupt an ongoing data transfer.
*/