linux-kernel - Re: [PATCH v2 03/14] rust: sync: add `Arc::as

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Message-ID: <20240921165801.1d1df6ab.gary@garyguo.net>
Date: Sat, 21 Sep 2024 16:58:01 +0100
From: Gary Guo <gary@...yguo.net>
To: Benno Lossin <benno.lossin@...ton.me>
Cc: Andreas Hindborg <a.hindborg@...nel.org>, Miguel Ojeda
 <ojeda@...nel.org>, Alex Gaynor <alex.gaynor@...il.com>, Anna-Maria Behnsen
 <anna-maria@...utronix.de>, Frederic Weisbecker <frederic@...nel.org>,
 Thomas Gleixner <tglx@...utronix.de>, Boqun Feng <boqun.feng@...il.com>,
 Björn Roy Baron <bjorn3_gh@...tonmail.com>, Alice Ryhl
 <aliceryhl@...gle.com>, rust-for-linux@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 03/14] rust: sync: add `Arc::as_ptr`

On Thu, 19 Sep 2024 14:03:50 +0000
Benno Lossin <benno.lossin@...ton.me> wrote:

> On 18.09.24 00:27, Andreas Hindborg wrote:
> > Add a method to get a pointer to the data contained in an `Arc`.
> > 
> > Signed-off-by: Andreas Hindborg <a.hindborg@...nel.org>
> > ---
> >  rust/kernel/sync/arc.rs | 8 ++++++++
> >  1 file changed, 8 insertions(+)
> > 
> > diff --git a/rust/kernel/sync/arc.rs b/rust/kernel/sync/arc.rs
> > index 3673496c2363..a57ea3e2b44c 100644
> > --- a/rust/kernel/sync/arc.rs
> > +++ b/rust/kernel/sync/arc.rs
> > @@ -258,6 +258,14 @@ pub fn into_raw(self) -> *const T {
> >          unsafe { core::ptr::addr_of!((*ptr).data) }
> >      }
> > 
> > +    /// Return a raw pointer to the data in this arc.
> > +    pub fn as_ptr(&self) -> *const T {  
> 
> I don't know if we have a convention for this, but shouldn't this be an
> associated function? Because if `T` also has an `as_ptr` function, it
> will be shadowed by this one. 

The usual Rust convention is usually that if `Deref` is implemented,
then unless there's a good reason to do otherwise, associated function
should be used.

Best,
Gary

> 
> ---
> Cheers,
> Benno
> 
> > +        let ptr = self.ptr.as_ptr();
> > +        // SAFETY: As we derive the pointer from a reference above, the pointer
> > +        // must be valid.
> > +        unsafe { core::ptr::addr_of!((*ptr).data) }
> > +    }
> > +
> >      /// Recreates an [`Arc`] instance previously deconstructed via [`Arc::into_raw`].
> >      ///
> >      /// # Safety
> > --
> > 2.46.0
> > 
> >   
>