Additional Features for USART Setup Function

[nixpulvis]

I'm trying to implement a USART setup function I had from C:

void uart_init(void) {
  UBRR0H = UBRRH_VALUE;
  UBRR0L = UBRRL_VALUE;
#if USE_2X
  // Double transmission speed.
  UCSR0A |= _BV(U2X0);
#else
  // Not double transmission speed.
  UCSR0A &= ~(_BV(U2X0));
#endif
  // 8-bit data.
  UCSR0C = _BV(UCSZ01) | _BV(UCSZ00);
  // Enable RX and TX.
  UCSR0B = _BV(RXEN0) | _BV(TXEN0);

  // The UART io.
  static FILE uart_io = FDEV_SETUP_STREAM(uart_put, uart_get, _FDEV_SETUP_RW);

  // Set this UART as stdout and stdin.
  stdout = &uart_io;
  stdin = &uart_io;
}

Seems like I need UBRRH_VALUE, UBRRL_VALUE from util/setbaud.h, which seems blacklisted to avoid preprocessor stuff.

libc/build.rs

Line 21 in 22322e0

"util/setbaud.h", // mostly made of preprocessor magic

It would be great if we could use things like cfg(USE_2X) (or something) to control this. Or is this possible somehow already?

Additionally, the IO hook fdev_setup_stream creates a stream I have set to STDIN and STDOUT, which would be nice to replicate. But the *io also seems blacklisted.

libc/build.rs

Line 139 in 22322e0

if stem.to_str().unwrap().starts_with("io") {

I'm not sure how the Rust AVR library organization is being planned, so this may be in the wrong place.

Thanks.