It would be useful to have the option for Semihosting to combine the different message parts into a single temporary buffer before calling WRITE. This would greatly decrease the pain factor due to the long roundtrip latency.

It would be extremely helpful to see how semihosting and itm works with this crate

The log-integration feature can not be enabled for the thumbv6m-none-eabi target (build fails).
The log::set_logger() is called which is available only if #[cfg(atomic_cas)].
The unsafe log::set_logger_racy() could be used on platforms without atomic_cas.
Do you plan to support the log-integration feature on Cortex-M0+ somehow?

Most likely writes underlying Stim should be guarded by some simple atomic and Itm destination can be marked as Sync

I was wondering if it is possible to provide a logger for a serial port or whether you already though about this. I'm new to Rust, so right now I am trying to figure out how to define a static logger which will needs to be able to be set by the user depending on which serial port could be used.