Logging

It would be nice to be able to use the logging macros from the log crate. We can do this by implementing the Log trait.

  1. use crate::pl011::Uart;
  2. use core::fmt::Write;
  3. use log::{LevelFilter, Log, Metadata, Record, SetLoggerError};
  4. use spin::mutex::SpinMutex;
  6. static LOGGER: Logger = Logger { uart: SpinMutex::new(None) };
  8. struct Logger {
  9.     uart: SpinMutex<Option<Uart>>,
  10. }
  12. impl Log for Logger {
  13.     fn enabled(&self, _metadata: &Metadata) -> bool {
  14.         true
  15.     }
  17.     fn log(&self, record: &Record) {
  18.         writeln!(
  19.             self.uart.lock().as_mut().unwrap(),
  20.             "[{}] {}",
  21.             record.level(),
  22.             record.args()
  23.         )
  24.         .unwrap();
  25.     }
  27.     fn flush(&self) {}
  28. }
  30. /// Initialises UART logger.
  31. pub fn init(uart: Uart, max_level: LevelFilter) -> Result<(), SetLoggerError> {
  32.     LOGGER.uart.lock().replace(uart);
  34.     log::set_logger(&LOGGER)?;
  35.     log::set_max_level(max_level);
  36.     Ok(())
  37. }
  • The unwrap in log is safe because we initialise LOGGER before calling set_logger.