Re: [net-next PATCH v11 1/6] net: phy: pass PHY driver to .match_phy_device OP

["Benno Lossin" <lossin@kernel.org>]

On Fri May 16, 2025 at 11:23 PM CEST, Christian Marangi wrote:
> diff --git a/rust/kernel/net/phy.rs b/rust/kernel/net/phy.rs
> index a59469c785e3..079a0f884887 100644
> --- a/rust/kernel/net/phy.rs
> +++ b/rust/kernel/net/phy.rs
> @@ -418,15 +418,18 @@ impl<T: Driver> Adapter<T> {
>  
>      /// # Safety
>      ///
> -    /// `phydev` must be passed by the corresponding callback in `phy_driver`.
> +    /// `phydev` and `phydrv` must be passed by the corresponding callback in
> +    //  `phy_driver`.
>      unsafe extern "C" fn match_phy_device_callback(
>          phydev: *mut bindings::phy_device,
> +        phydrv: *const bindings::phy_driver,
>      ) -> crate::ffi::c_int {
>          // SAFETY: This callback is called only in contexts
>          // where we hold `phy_device->lock`, so the accessors on
>          // `Device` are okay to call.
>          let dev = unsafe { Device::from_raw(phydev) };
> -        T::match_phy_device(dev) as i32
> +        let drv = unsafe { T::from_raw(phydrv) };
> +        T::match_phy_device(dev, drv) as i32
>      }
>  
>      /// # Safety
> @@ -574,6 +577,19 @@ pub const fn create_phy_driver<T: Driver>() -> DriverVTable {
>  /// This trait is used to create a [`DriverVTable`].
>  #[vtable]
>  pub trait Driver {
> +    /// # Safety
> +    ///
> +    /// For the duration of `'a`, the pointer must point at a valid
> +    /// `phy_driver`, and the caller must be in a context where all
> +    /// methods defined on this struct are safe to call.
> +    unsafe fn from_raw<'a>(ptr: *const bindings::phy_driver) -> &'a DriverVTable {
> +        // CAST: `DriverVTable` is a `repr(transparent)` wrapper around `bindings::phy_driver`.
> +        let ptr = ptr.cast::<DriverVTable>();
> +        // SAFETY: by the function requirements the pointer is const and is
> +        // always valid to access for the duration of `'a`.
> +        unsafe { &*ptr }
> +    }

If we go the way of supplying a `&DriverVTable` in the
`match_phy_device` function, then this should be a function in the impl
block of `DriverVTable` and not in `Driver`.

See my reply to Fujita on the previous version, I don't think that we
need to add the `DriverVTable` to the `match_phy_device` function if we
don't provide accessor methods. Currently that isn't needed, so you only
need the hunks above this one. (I'd wait for Fujita's reply though).

---
Cheers,
Benno

> +
>      /// Defines certain other features this PHY supports.
>      /// It is a combination of the flags in the [`flags`] module.
>      const FLAGS: u32 = 0;
> @@ -602,7 +618,7 @@ fn get_features(_dev: &mut Device) -> Result {
>  
>      /// Returns true if this is a suitable driver for the given phydev.
>      /// If not implemented, matching is based on [`Driver::PHY_DEVICE_ID`].
> -    fn match_phy_device(_dev: &Device) -> bool {
> +    fn match_phy_device(_dev: &mut Device, _drv: &DriverVTable) -> bool {
>          false
>      }
>