ENCRYPTION_USAGE
ret = _get_derived_key(context, crypto, ENCRYPTION_USAGE(usage), &dkey);
ret = _get_derived_key(context, crypto, ENCRYPTION_USAGE(usage), &dkey);
ret = _get_derived_key(context, crypto, ENCRYPTION_USAGE(usage), &dkey);
ret = _get_derived_key(context, crypto, ENCRYPTION_USAGE(usage), &dkey);