Comment by pornel

It's not hard to just call C. Rust supports C ABI and there's tooling for converting between C headers and Rust interfaces.

The challenging part is making a higher-level "safe" Rust API around the C API. Safe in the sense that it fully uses Rust's type system, lifetimes, destructors, etc. to uphold the safety guarantees that Rust gives and make it hard to misuse the API.

But the objections about Rust in the kernel weren't really about the difficulty of writing the Rust code, but more broadly about having Rust there at all.