Re: [PATCH] rust: clk: use the type-state pattern

[Daniel Almeida <daniel.almeida@collabora.com>]

[…]

>         }
> 
> -        /// Enable the clock.
> +        /// Attempts to convert the [`Clk`] to a [`Prepared`] state.
>         ///
> -        /// Equivalent to the kernel's [`clk_enable`] API.
> +        /// Equivalent to the kernel's [`clk_prepare`] API.
>         ///
> -        /// [`clk_enable`]: https://docs.kernel.org/core-api/kernel-api.html#c.clk_enable
> +        /// [`clk_prepare`]: https://docs.kernel.org/core-api/kernel-api.html#c.clk_prepare
>         #[inline]
> -        pub fn enable(&self) -> Result {
> -            // SAFETY: By the type invariants, self.as_raw() is a valid argument for
> -            // [`clk_enable`].
> -            to_result(unsafe { bindings::clk_enable(self.as_raw()) })
> +        pub fn prepare(self) -> Result<Clk<Prepared>, Error<Unprepared>> {
> +            // We will be transferring the ownership of our `clk_get()` count to
> +            // `Clk<Prepared>`.
> +            let clk = ManuallyDrop::new(self);
> +
> +            // SAFETY: By the type invariants, self.0 is a valid argument for [`clk_prepare`].

I just noticed that some comments still refer to the old “self.0” field, but that doesn’t exist anymore.

I’ll fix that in v2.

> +            to_result(unsafe { bindings::clk_prepare(clk.as_raw()) })
> +                .map(|()| Clk {
> +                    inner: clk.inner,
> +                    _phantom: PhantomData,
> +                })
> +                .map_err(|error| Error {
> +                    error,
> +                    clk: ManuallyDrop::into_inner(clk),
> +                })
>         }
> +    }
> 

— Daniel