Re: [PATCH v3] rust: regulator: add a bare minimum regulator abstraction

[Benno Lossin]

On Mon May 19, 2025 at 11:56 AM CEST, Mark Brown wrote:
> On Sun, May 18, 2025 at 04:04:24PM +0200, Benno Lossin wrote:
>
>> I'm not sure if I understand correctly, so I'll just try to echo it and
>> see if it's correct :)
>
>> The `enable`/`disable` functions change a refcount on the underlying
>> regulator that tracks if the regulator actually is enabled/disabled.
>> Asking the hardware to enable or disable a regulator can fail, but if we
>> already know that it is enabled, only the refcount is incremented.
>
> Yes.
>
>>     It's okay to leak this enabled-refcount, since when the regulators
>> actual refcount (so the one adjusted by `_get` & `_put`) hits zero, we
>> can also disable the regulator. So the enabled-refcount is essentially a
>> weak refcount that only does something while the regulator exists.
>
> No.  You should not leak any refcount, the per consumer refcount
> duplicates what's being done for the regulator as a whole, one should
> never be incremented or decremented without the other (but there may be
> multiple consumers to choose from).

What stops the last `regulator_put` to also call `regulator_disable` a
correct number of times?

What are the kinds of problems that one could encounter when not calling
`regulator_disable` before `regulator_put` or if `regulator_enable` was
never called to begin with?
    I'm asking, because if the answer is "memory bugs", then we'll need
to make the abstraction such that users cannot misuse the enable/disable
calls (or make those calls `unsafe`).

---
Cheers,
Benno