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

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Message-ID: <682755d8.050a0220.3c78c8.a604@mx.google.com>
Date: Fri, 16 May 2025 17:12:19 +0200
From: Christian Marangi <ansuelsmth@...il.com>
To: Benno Lossin <lossin@...nel.org>
Cc: FUJITA Tomonori <fujita.tomonori@...il.com>, 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,
	bcm-kernel-feedback-list@...adcom.com, kabel@...nel.org,
	andrei.botila@....nxp.com, tmgross@...ch.edu, ojeda@...nel.org,
	alex.gaynor@...il.com, boqun.feng@...il.com, gary@...yguo.net,
	bjorn3_gh@...tonmail.com, benno.lossin@...ton.me,
	a.hindborg@...nel.org, aliceryhl@...gle.com, dakr@...nel.org,
	sd@...asysnail.net, michael@...sekall.de, daniel@...rotopia.org,
	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 04:48:53PM +0200, Benno Lossin wrote:
> 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`?
> 

Is this referred to a problem with using from_raw or more of a general
question on how the rust wrapper are done for phy code?

> >>      /// 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.
>

I think

fn match_phy_device(_dev: &mut Device, _drv: &Self) -> bool

more resemble the C parallel function so I think this suite the best,
should make it easier to port if ever (am I wrong?)

-- 
	Ansuel