Re: [RFC PATCH 2/3] rust: introduce WMI abstractions

[Gladyshev Ilya]

On 12/25/25 21:06, Armin Wolf wrote:
> > +// SAFETY: A call to `unregister` for a given instance of `RegType` 
> > is guaranteed to be valid if
> > +// a preceding call to `register` has been successful.
> > +unsafe impl<T: Driver + 'static> driver::RegistrationOps for 
> > Adapter<T> {
> > +    type RegType = bindings::wmi_driver;
> > +
> > +    unsafe fn register(
> > +        wdrv: &Opaque<Self::RegType>,
> > +        name: &'static CStr,
> > +        module: &'static ThisModule,
> > +    ) -> Result {
> > +        macro_rules! map_callback {
> > +            ($flag:ident -> $callback:ident) => {
> > +                if T::$flag {
> > +                    Some(Self::$callback)
> > +                } else {
> > +                    None
> > +                }
> > +            };
> > +        }
> > +
> > +        // SAFETY: It's safe to set the fields of `struct wmi_driver` 
> > on initialization.
> > +        unsafe {
> > +            (*wdrv.get()).driver.name = name.as_char_ptr();
> > +            (*wdrv.get()).driver.probe_type = 
> > bindings::probe_type_PROBE_PREFER_ASYNCHRONOUS;
> > +            (*wdrv.get()).id_table = T::TABLE.as_ptr();
> > +            (*wdrv.get()).probe = map_callback!(HAS_PROBE -> 
> > probe_callback);
> > +            (*wdrv.get()).notify = map_callback!(HAS_NOTIFY -> 
> > notify_callback);
>
> I think it should be possible to handle WMI drivers 
> requiring .no_notify_data to be set. Is there
> a way to declare the WMI event data passed to the notify() callback as 
> optional? If yes, then i suggest
> that we always set .no_notify_data and simply require the WMI drivers 
> themselves to verify that a given
> WMI event does contain additional event data.

Yes, I can change the notify API to receive Optional<&AcpiBuffer> 
instead of &AcpiBuffer, so every driver will be forced to verify payload 
existence by Rust's type system.

IIRC, casting raw (C) pointer to Optional<&T> is actually a no-op in 
Rust, since NULL is automatically mapped to None (empty Optional), so it 
will be a zero-cost typesystem win :)