The xpt driver provides a way for userland applications to issue certain CAM CCBs to the kernel.
Since the xpt driver allows direct access to the CAM subsystem, system administrators should exercise caution when granting access to this driver. If used improperly, this driver can allow userland applications to crash a machine or cause data loss.
There is no kernel configuration required for the xpt driver. It is enabled when SCSI support is enabled in the kernel. There is one instance of the xpt driver per CAM transport layer instance. Since there is currently only one CAM transport layer, there will only be one instance of this driver.