linux-kernel - Re: [PATCH v2 1/2] rust: Update PCI binding safety comments and add inline compiler hint

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Message-Id: <DB87TX9Y5018.N1WDM8XRN74K@kernel.org>
Date: Thu, 10 Jul 2025 10:01:05 +0200
From: "Benno Lossin" <lossin@...nel.org>
To: "Alistair Popple" <apopple@...dia.com>, <rust-for-linux@...r.kernel.org>
Cc: "Danilo Krummrich" <dakr@...nel.org>, "Bjorn Helgaas"
 <bhelgaas@...gle.com>, Krzysztof Wilczyński
 <kwilczynski@...nel.org>, "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>, "Andreas Hindborg" <a.hindborg@...nel.org>,
 "Alice Ryhl" <aliceryhl@...gle.com>, "Trevor Gross" <tmgross@...ch.edu>,
 "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>, "Rafael J. Wysocki"
 <rafael@...nel.org>, "John Hubbard" <jhubbard@...dia.com>, "Alexandre
 Courbot" <acourbot@...dia.com>, <linux-pci@...r.kernel.org>,
 <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 1/2] rust: Update PCI binding safety comments and add
 inline compiler hint

On Thu Jul 10, 2025 at 4:24 AM CEST, Alistair Popple wrote:
> diff --git a/rust/kernel/pci.rs b/rust/kernel/pci.rs
> index 8435f8132e38..5c35a66a5251 100644
> --- a/rust/kernel/pci.rs
> +++ b/rust/kernel/pci.rs
> @@ -371,14 +371,18 @@ fn as_raw(&self) -> *mut bindings::pci_dev {
>  
>  impl Device {
>      /// Returns the PCI vendor ID.
> +    #[inline]
>      pub fn vendor_id(&self) -> u16 {
> -        // SAFETY: `self.as_raw` is a valid pointer to a `struct pci_dev`.
> +        // SAFETY: by its type invariant `self.as_raw` is always a valid pointer to a

s/by its type invariant/by the type invariants of `Self`,/
s/always//

Also, which invariant does this refer to? The only one that I can see
is:

    /// A [`Device`] instance represents a valid `struct device` created by the C portion of the kernel.

And this doesn't say anything about the validity of `self.as_raw()`...

> +        // `struct pci_dev`.
>          unsafe { (*self.as_raw()).vendor }
>      }
>  
>      /// Returns the PCI device ID.
> +    #[inline]
>      pub fn device_id(&self) -> u16 {
> -        // SAFETY: `self.as_raw` is a valid pointer to a `struct pci_dev`.
> +        // SAFETY: by its type invariant `self.as_raw` is always a valid pointer to a
> +        // `struct pci_dev`.

Ditto here.

---
Cheers,
Benno

>          unsafe { (*self.as_raw()).device }
>      }
>