A driver might also register device IDs for devices that do not directly supply a unique ID. Registering these IDs requires the device to be capable of storing and retrieving a small amount of data in a reserved area. The driver can then create a fabricated device ID and write it to the reserved area.
/* * the device doesn't supply a unique ID, attempt to read * a fabricated ID from the device's reserved data. */ if (xxx_read_deviceid(un, &devid_buf) == XXX_OK) { if (ddi_devid_valid(devid_buf) == DDI_SUCCESS) { devid_sz = ddi_devi_sizeof(devid_buf); un->un_devid = kmem_alloc(devid_sz, KM_SLEEP); bcopy(devid_buf, un->un_devid, devid_sz); ddi_devid_register(dip, un->un_devid); return (XXX_OK); } } /* * we failed to read a valid device ID from the device * fabricate an ID, store it on the device, and register * it with the DDI */ if (ddi_devid_init(dip, DEVID_FAB, 0, NULL, &un->un_devid) == DDI_FAILURE) { return (XXX_FAILURE); } if (xxx_write_deviceid(un) != XXX_OK) { ddi_devid_free(un->un_devid); un->un_devid = NULL; return (XXX_FAILURE); } ddi_devid_register(dip, un->un_devid); return (XXX_OK);