// Feature register defines for SMART "sub commands"
  READ_ATTRIBUTES             = $D0;
  READ_THRESHOLDS             = $D1;
  ENABLE_DISABLE_AUTOSAVE     = $D2;
  SAVE_ATTRIBUTE_VALUES       = $D3;
  EXECUTE_OFFLINE_DIAGS       = $D4;
  SMART_READ_LOG              = $D5;
  SMART_WRITE_LOG             = $d6;
  ENABLE_SMART                = $D8;
  DISABLE_SMART               = $D9;
  RETURN_SMART_STATUS         = $DA;
  ENABLE_DISABLE_AUTO_OFFLINE = $DB;