Why not use OwnedFd and BorrowFd instead of RawFd for fd params?

[creonico]

I just learned that OwnedFd and BorrowedFd are I/O safe alternatives to RawFd, especially for FFI, https://rust-lang.github.io/rfcs/3128-io-safety.html#ownedfd-and-borrowedfdfd-1. So why not use this types instead? For example, currently mmap receives a file descriptor parameter as an i32,

pub unsafe extern "C" fn mmap(
    addr: *mut c_void,
    len: size_t,
    prot: c_int,
    flags: c_int,
    fd: c_int,
    offset: off_t
) -> *mut c_void

But why not define it with OwnedFd or BorrowedFd instead as in this examples: https://github.com/sunfishcode/io-lifetimes?tab=readme-ov-file#the-magic-of-transparency.
Please accept my apology for any oversight on my part, especially if there is an evident explanation for the situation as it stands.

[magicant]

This crate is intended to expose the raw API of the underlying platform. If you want a fancy, safe API, you can use nix or rustix.