How to modify device parameters or stop the device during data reading?

for the example:
examples\read_serialport.rs

``` rust
poll.registry()
        .register(&mut rx, SERIAL_TOKEN, Interest::READABLE)
        .unwrap();
loop {
        poll.poll(&mut events, None)?;
        // handle the read event
        // ...
}
```
How to modify device parameters or stop the device during data reading?

Any good ideas for implementing this? thanks~
