Re: [PATCH v2 2/3] rust: platform: wire runtime PM callbacks

[Alice Ryhl <aliceryhl@google.com>]

On Tue, Jul 21, 2026 at 05:34:03PM +0200, Beata Michalska wrote:
> Allow Rust platform drivers to expose runtime PM callbacks to the driver core.
> 
> The runtime PM abstraction builds a dev_pm_ops table for the concrete driver
> implementation, but the platform bus still needs to receive that table through
> struct platform_driver. Add an optional PM_OPS associated constant to
> platform::Driver and initialize the coresponding C device_driver struct
> accordingly during registration. The platform glue only wires the callback
> table into the C driver model; ownership of the callback payload and
> runtime PM teardown remain with the pm module.
> 
> Signed-off-by: Beata Michalska <beata.michalska@arm.com>
> ---
>  rust/kernel/platform.rs | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/rust/kernel/platform.rs b/rust/kernel/platform.rs
> index d8d48f60b0b9..b7e422388634 100644
> --- a/rust/kernel/platform.rs
> +++ b/rust/kernel/platform.rs
> @@ -72,6 +72,11 @@ unsafe fn register(
>              None => core::ptr::null(),
>          };
>  
> +        let pm_ops = match T::PM_OPS {
> +            Some(ops) => ops,
> +            None => core::ptr::null(),
> +        };

This value is just any user-provided &bindings::pm_ops, which I think is
too lax. There is no guarantee that the Registration and the PM_OPS
table agree on what the type T is, which can lead to type confusion.

Most likely, you must instead give `trait Driver` an associated type
saying "the PmOps type is this particular type", and then here you can
do `Some(T::PM_OPS)` to actually get the associated table.

And then in the registration, you can further require that the types
also match there. E.g., maybe make the registration generic over the
Driver type and then the inner type T is just D::PmData or similar.

Alice

>          // SAFETY: It's safe to set the fields of `struct platform_driver` on initialization.
>          unsafe {
>              (*pdrv.get()).driver.name = name.as_char_ptr();
> @@ -79,6 +84,7 @@ unsafe fn register(
>              (*pdrv.get()).remove = Some(Self::remove_callback);
>              (*pdrv.get()).driver.of_match_table = of_table;
>              (*pdrv.get()).driver.acpi_match_table = acpi_table;
> +            (*pdrv.get()).driver.pm = pm_ops;
>          }
>  
>          // SAFETY: `pdrv` is guaranteed to be a valid `DriverType`.
> @@ -222,6 +228,9 @@ pub trait Driver {
>      /// The table of ACPI device ids supported by the driver.
>      const ACPI_ID_TABLE: Option<acpi::IdTable<Self::IdInfo>> = None;
>  
> +    /// Runtime PM callbacks
> +    const PM_OPS: Option<&'static bindings::dev_pm_ops> = None;
> +
>      /// Platform driver probe.
>      ///
>      /// Called when a new platform device is added or discovered.
> -- 
> 2.43.0
>