So, I peeked into the documentation of volatile_register. The unsafe is there for a clear reason: the compiler can't verify that you aren't creating a mapping to some memory location that is used by the program itself. If you are allowed to safely create a mapping to, for example, a local variable and safely modify it using `register.write()`, you have UB, and that's all in safe code!

So, this isn't a case that the `unsafe` is there just as a warning lint, it has an actual meaning, protecting the memory safety invariants.