Registering a Fabricated ID

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);