netdev - Re: [PATCH net-next v4 3/6] rust: net::phy implement AsRef<kernel::device::Device> trait

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Message-ID: <3feed4bb-6298-4379-8a71-0b88437b6250@proton.me>
Date: Sun, 18 Aug 2024 15:55:31 +0000
From: Benno Lossin <benno.lossin@...ton.me>
To: FUJITA Tomonori <fujita.tomonori@...il.com>
Cc: netdev@...r.kernel.org, rust-for-linux@...r.kernel.org, andrew@...n.ch, tmgross@...ch.edu, miguel.ojeda.sandonis@...il.com, aliceryhl@...gle.com
Subject: Re: [PATCH net-next v4 3/6] rust: net::phy implement AsRef<kernel::device::Device> trait

On 18.08.24 13:25, FUJITA Tomonori wrote:
> On Sun, 18 Aug 2024 10:42:32 +0000
> Benno Lossin <benno.lossin@...ton.me> wrote:
> 
>>> /// - Referencing a `phy_device` using this struct asserts that you are in
>>> ///   a context where all methods defined on this struct are safe to call.
>>> /// - This struct always has a valid `mdio.dev`.
>>
>> Hmm, I think `self.0.mdio.dev` would be clearer.
> 
> Sure, fixed.
> 
>>> /// # Safety
>>> ///
>>> /// For the duration of 'a,
>>> /// - the pointer must point at a valid `phy_device`, and the caller
>>> ///   must be in a context where all methods defined on this struct
>>> ///   are safe to call.
>>> /// - 'mdio.dev' must be a valid.
>>
>> Also here: `(*ptr).mdio.dev`.
> 
> Thanks, looks better.
> 
> Here's an updated patch.
> 
> diff --git a/rust/kernel/net/phy.rs b/rust/kernel/net/phy.rs
> index 5e8137a1972f..ec337cbd391b 100644
> --- a/rust/kernel/net/phy.rs
> +++ b/rust/kernel/net/phy.rs
> @@ -7,8 +7,7 @@
>  //! C headers: [`include/linux/phy.h`](srctree/include/linux/phy.h).
> 
>  use crate::{error::*, prelude::*, types::Opaque};
> -
> -use core::marker::PhantomData;
> +use core::{marker::PhantomData, ptr::addr_of_mut};
> 
>  /// PHY state machine states.
>  ///
> @@ -58,8 +57,9 @@ pub enum DuplexMode {
>  ///
>  /// # Invariants
>  ///
> -/// Referencing a `phy_device` using this struct asserts that you are in
> -/// a context where all methods defined on this struct are safe to call.
> +/// - Referencing a `phy_device` using this struct asserts that you are in
> +///   a context where all methods defined on this struct are safe to call.
> +/// - This struct always has a valid `self.0.mdio.dev`.
>  ///
>  /// [`struct phy_device`]: srctree/include/linux/phy.h
>  // During the calls to most functions in [`Driver`], the C side (`PHYLIB`) holds a lock that is
> @@ -76,9 +76,11 @@ impl Device {
>      ///
>      /// # Safety
>      ///
> -    /// For the duration of 'a, the pointer must point at a valid `phy_device`,
> -    /// and the caller must be in a context where all methods defined on this struct
> -    /// are safe to call.
> +    /// For the duration of 'a,
> +    /// - the pointer must point at a valid `phy_device`, and the caller
> +    ///   must be in a context where all methods defined on this struct
> +    ///   are safe to call.
> +    /// - `(*ptr).mdio.dev` must be a valid.
>      unsafe fn from_raw<'a>(ptr: *mut bindings::phy_device) -> &'a mut Self {
>          // CAST: `Self` is a `repr(transparent)` wrapper around `bindings::phy_device`.
>          let ptr = ptr.cast::<Self>();
> @@ -302,6 +304,14 @@ pub fn genphy_read_abilities(&mut self) -> Result {
>      }
>  }
> 
> +impl AsRef<kernel::device::Device> for Device {
> +    fn as_ref(&self) -> &kernel::device::Device {
> +        let phydev = self.0.get();
> +        // SAFETY: The struct invariant ensures that `mdio.dev` is valid.
> +        unsafe { kernel::device::Device::as_ref(addr_of_mut!((*phydev).mdio.dev)) }
> +    }
> +}
> +
>  /// Defines certain other features this PHY supports (like interrupts).
>  ///
>  /// These flag values are used in [`Driver::FLAGS`].
> --
> 2.34.1
> 

This looks, good, if you want, you can add my reviewed-by on this patch.

---
Cheers,
Benno