static ssize_t uart_mode_show(struct device *dev,
	struct device_attribute *attr, char *buf)
{
	struct usb_serial_port *port = to_usb_serial_port(dev);
	struct edgeport_port *edge_port = usb_get_serial_port_data(port);

	return sprintf(buf, "%d\n", edge_port->bUartMode);
}

The product subtracts one value from another, such that the result is less than the minimum allowable integer value, which produces a value that is not equal to the correct result.