Re: Question about compilation

[Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>]

On Thu, Oct 21, 2021 at 3:56 AM Amy Parker
<apark0006@student.cerritos.edu> wrote:
>
> So how do the Rust versions get linked over the C editions? How does
> it become that the Rust variant is the one actually executing at
> runtime?

If you are asking about the code inside `rust/`, then there is no
override happening, i.e. that code is, for the most part, not a
substitute for C code. Instead, they are wrappers ("abstractions")
over the C APIs so that other Rust code (outside `rust/`) can safely
use those facilities (for the most part). For instance,
`rust/kernel/sync/mutex.rs` is implemented using the C `struct mutex`.

If you are asking about code outside `rust/`, e.g. a driver module,
then yes, you may have a substitute for a C one. For that, you can use
Kconfig as usual (e.g. via separate option, or with a sub-option
toggle if they are exclusive or perhaps a `choice`, etc.). So no
special magic here -- an `.rs` file in e.g. `obj-y` will get compiled
as the root crate for your module.

Hope that clarifies!

Cheers,
Miguel