Re: [PATCH v10 1/5] rust: types: Add Ownable/Owned types

["Benno Lossin" <lossin@kernel.org>]

On Wed Jun 18, 2025 at 11:34 AM CEST, Oliver Mangold wrote:
> On 250514 1132, Benno Lossin wrote:
>> On Fri May 2, 2025 at 11:02 AM CEST, Oliver Mangold wrote:
>> 
>> > +/// - That the C code follows the usual mutable reference requirements. That is, the kernel will
>> > +///   never mutate the [`Ownable`] (excluding internal mutability that follows the usual rules)
>> > +///   while Rust owns it.
>> 
>> I feel like this requirement is better put on the `Owned::from_raw`
>> function.
>
> Thinking about it some more, the problem I see here is that if the type
> implements `OwnableMut` this requirement changes from "never mutate" to
> "never access at all".
>
> The safety requirements between `Ownable`, `OwnableMut`, `RefCounted`,
> `OwnableRefCounted` and `AlwaysRefCounted` are interacting, but I agree
> that, when looking at it a certain way, `Owned::from_raw()` is the place
> where one would expect these to be. I'm not sure anymore what is best here
> :/

I still think `Owned::from_raw` is the correct place to put this.

>
>> > +pub unsafe trait OwnableMut: Ownable {}
>> 
>> I don't like the name, but at the same time I also have no good
>> suggestion :( I'll think some more about it.
>
> There was already a bit of discussion about it. I had my own implementation of this
> where I used the names `UniqueRefCounted` and `UniqueRef`, but after discovering
> this version from Asahi Lina, I took it as it was, keeping the name.
>
> No one else came up with different suggestions so far, so maybe we should just leave it
> at `Owned`/`Ownable`?

I'm just hung up on the `Mut` part... Haven't come up with a good
replacement yet.

---
Cheers,
Benno