UMP_STREAM_PKT_BYTES
memset(buf, 0, UMP_STREAM_PKT_BYTES);
req->length += UMP_STREAM_PKT_BYTES;
if (++pos == UMP_STREAM_PKT_BYTES) {
req->length += UMP_STREAM_PKT_BYTES;
if (midi2->info.req_buf_size - req->length < UMP_STREAM_PKT_BYTES)