linux-kernel - Re: [PATCH v8] rust: transmute: Add methods for FromBytes trait

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Message-Id: <DBR3913BFPSK.18K4JBYOPQVRG@nvidia.com>
Date: Fri, 01 Aug 2025 21:26:22 +0900
From: "Alexandre Courbot" <acourbot@...dia.com>
To: "Christian S. Lima" <christiansantoslima21@...il.com>, "Miguel Ojeda"
 <ojeda@...nel.org>, "Alex Gaynor" <alex.gaynor@...il.com>, "Boqun Feng"
 <boqun.feng@...il.com>, "Gary Guo" <gary@...yguo.net>,
 Björn Roy Baron <bjorn3_gh@...tonmail.com>, "Benno Lossin"
 <benno.lossin@...ton.me>, "Andreas Hindborg" <a.hindborg@...nel.org>,
 "Alice Ryhl" <aliceryhl@...gle.com>, "Trevor Gross" <tmgross@...ch.edu>,
 "Danilo Krummrich" <dakr@...nel.org>, <rust-for-linux@...r.kernel.org>,
 <linux-kernel@...r.kernel.org>, <~lkcamp/patches@...ts.sr.ht>,
 <richard120310@...il.com>
Subject: Re: [PATCH v8] rust: transmute: Add methods for FromBytes trait

Hi Christian,

Any plan for a v9 soon? I would like to make sure we secure this into
the Nova tree as we are highly dependent on this feature.

On Tue Jun 24, 2025 at 1:28 PM JST, Christian S. Lima wrote:
<snip>
> +// SAFETY: All bit patterns are acceptable values of the types and in array case if all bit patterns
> +// are acceptable for individual values in an array, then all bit patterns are also acceptable
> +// for arrays of that type.
> +unsafe impl<T> FromBytes for T
> +where
> +    T: FromBytesSized,
> +{
> +    fn from_bytes(bytes: &[u8]) -> Option<&Self> {
> +        let slice_ptr = bytes.as_ptr().cast::<T>();
> +        if bytes.len() == ::core::mem::size_of::<T>() && slice_ptr.is_aligned() {

Another small nit: this is not a macro, so you don't need to use the
`::` prefix here. Actually even `size_of::<T>()` seems to work.