linux-kernel - Re: [net-next PATCH v10 7/7] rust: net::phy sync with match_phy

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Message-Id: <D9XO2721HEQI.3BGSHJXCHPTL@kernel.org>
Date: Fri, 16 May 2025 16:48:53 +0200
From: "Benno Lossin" <lossin@...nel.org>
To: "FUJITA Tomonori" <fujita.tomonori@...il.com>, <ansuelsmth@...il.com>
Cc: <andrew+netdev@...n.ch>, <davem@...emloft.net>, <edumazet@...gle.com>,
 <kuba@...nel.org>, <pabeni@...hat.com>, <robh@...nel.org>,
 <krzk+dt@...nel.org>, <conor+dt@...nel.org>, <hkallweit1@...il.com>,
 <linux@...linux.org.uk>, <florian.fainelli@...adcom.com>,
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 <netdev@...r.kernel.org>, <devicetree@...r.kernel.org>,
 <linux-kernel@...r.kernel.org>, <rust-for-linux@...r.kernel.org>
Subject: Re: [net-next PATCH v10 7/7] rust: net::phy sync with
 match_phy_device C changes

On Fri May 16, 2025 at 2:30 PM CEST, FUJITA Tomonori wrote:
> On Thu, 15 May 2025 13:27:12 +0200
> Christian Marangi <ansuelsmth@...il.com> wrote:
>> @@ -574,6 +577,23 @@ 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 Self
>> +    where
>> +        Self: Sized,
>> +    {
>> +        // CAST: `Self` is a `repr(transparent)` wrapper around `bindings::phy_driver`.
>> +        let ptr = ptr.cast::<Self>();
>> +        // SAFETY: by the function requirements the pointer is valid and we have unique access for
>> +        // the duration of `'a`.
>> +        unsafe { &*ptr }
>> +    }
>
> We might need to update the comment. phy_driver is const so I think
> that we can access to it any time.

Why is any type implementing `Driver` a transparent wrapper around
`bindings::phy_driver`?

>>      /// Defines certain other features this PHY supports.
>>      /// It is a combination of the flags in the [`flags`] module.
>>      const FLAGS: u32 = 0;
>> @@ -602,7 +622,7 @@ 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<T: Driver>(_dev: &mut Device, _drv: &T) -> bool {
>>          false
>>      }
>
> I think that it could be a bit simpler:
>
> fn match_phy_device(_dev: &mut Device, _drv: &Self) -> bool
>
> Or making it a trait method might be more idiomatic?
>
> fn match_phy_device(&self, _dev: &mut Device) -> bool

Yeah that would make most sense.

---
Cheers,
Benno