Because SCSI devices are not self-identifying, a hardware configuration file is required for a target driver. See the driver.conf(4) and scsi_free_consistent_buf(9F) man pages for details. The following is a typical configuration file:
name="xx" class="scsi" target=2 lun=0;
The system reads the file during autoconfiguration. The system uses the class property to identify the driver's possible parent. Then, the system attempts to attach the driver to any parent driver that is of class scsi. All host bus adapter drivers are of this class. Using the class property rather than the parent property is preferred. This approach enables any host bus adapter driver that finds the expected device at the specified target and lun IDs to attach to the target. The target driver is responsible for verifying the class in its probe(9E) routine.