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

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

>> Yes, that would be great. I do wonder though if it wouldn't make sense
>> to turn it the other way around. It creates a fair share of boilerplate
>> for a number of drivers. Can't we keep Clk the way it is as a
>> lower-level type, and crate a ManagedClk (or whatever name you prefer)
>> that drivers can use, and would be returned by higher-level helpers, if
>> they so choose?
>> 
>> That way, we do have the typestate API for whoever wants to, without
>> creating too much boilerplate for everybody else.
> 
> One solution is to have a new typestate `Dynamic` which opts to track things
> using variables.
> 
> struct Dynamic {
>    enabled: bool,
>    prepared: bool,
> }
> 
> trait ClkState {
>    // Change to methods
>    fn disable_on_drop(&self) -> bool;
> }
> 
> struct Clk<State> {
>    ...
>    // Keep an instance, which is zero-sized for everything except `Dynamic`
>    state: State,
> }
> 
> this way we can have runtime-checked state conversions.
> 
> Best,
> Gary

There used to be a Dynamic state in the past in a similar setting. That was removed after some thorough discussion. I’d say we should refrain from going back to this. Specially considering that the current design works fine.

 I can remove the turbofish if you want, even though I think they’re useful so that we have the same API for all states.

— Daniel