[PATCH v3 1/3] rust: clk: use the type-state pattern

[Alice Ryhl]

On Thu, Feb 12, 2026 at 2:38 PM Maxime Ripard <mripard at kernel.org> wrote:
>
> Hi Alice,
>
> On Thu, Feb 12, 2026 at 09:16:51AM +0100, Alice Ryhl wrote:
> > If you make the raw API unsafe, then that's okay but any use of an
> > unsafe API from a driver will receive very hard scrutiny.
>
> And that's totally fair to me. If drivers want to have a more optimal
> but potentially unsafe use of the API, then it should be flagged,
> documented and scrutinized.
>
> > Yes, there are occasionally good reasons to use unsafe from drivers,
> > but the entire point of this Rust exercise is to isolate unsafe code
> > outside of drivers as much as possible.
>
> So, aside from the risk of fuckups, are you concerned about something
> here? Do you expect that scrutiny to be constly on the maintenance side
> of things?

Well I do think it's mostly the risk of mistakes, yes.

> I guess what I'm asking is: except for the obvious "review" cost
> associated with it, why would that be a probleme if we have, say, a few
> dozen drivers using that unsafe API?

The reason I wouldn't really suggest the unsafe API is that, if I'm
the reviewer of said driver, then my review will be "just use a safe
API instead".

For example, if you really want explicit inc/dec calls for
convenience, we can make a safe API with a counter that returns an
error if you decrement more times than you have previously
incremented. Or if you prefer something else, I can think of several
other safe APIs.

> > If Daniel's proposal is inconvenient for some drivers, it would be far
> > better to have a third API that is both safe and convenient for those
> > drivers.
>
> Yeah, I guess I was expecting that one to come after we have a few
> unsafe drivers using it and we do need to consolidate / make it safe.

For most things, we implemented and used the safe API from the very
start. I'm not going to say there are never exceptions to that because
there *are* exceptions. But I don't really see why clk should be one
of them.

Alice