linux-kernel - Re: [PATCH 1/3] rust: pci: implement TryInto<IrqRequest<'a>> for IrqVector<'a>

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Message-ID: <aPEIxYlh98exA2vn@google.com>
Date: Thu, 16 Oct 2025 15:01:25 +0000
From: Alice Ryhl <aliceryhl@...gle.com>
To: Danilo Krummrich <dakr@...nel.org>
Cc: bhelgaas@...gle.com, kwilczynski@...nel.org, ojeda@...nel.org, 
	alex.gaynor@...il.com, boqun.feng@...il.com, gary@...yguo.net, 
	bjorn3_gh@...tonmail.com, lossin@...nel.org, a.hindborg@...nel.org, 
	tmgross@...ch.edu, rust-for-linux@...r.kernel.org, linux-pci@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] rust: pci: implement TryInto<IrqRequest<'a>> for IrqVector<'a>

On Wed, Oct 15, 2025 at 08:14:29PM +0200, Danilo Krummrich wrote:
> Implement TryInto<IrqRequest<'a>> for IrqVector<'a> to directly convert
> a pci::IrqVector into a generic IrqRequest, instead of taking the
> indirection via an unrelated pci::Device method.
> 
> Signed-off-by: Danilo Krummrich <dakr@...nel.org>
> ---
>  rust/kernel/pci.rs | 38 ++++++++++++++++++--------------------
>  1 file changed, 18 insertions(+), 20 deletions(-)
> 
> diff --git a/rust/kernel/pci.rs b/rust/kernel/pci.rs
> index d91ec9f008ae..c6b750047b2e 100644
> --- a/rust/kernel/pci.rs
> +++ b/rust/kernel/pci.rs
> @@ -596,6 +596,20 @@ fn index(&self) -> u32 {
>      }
>  }
>  
> +impl<'a> TryInto<IrqRequest<'a>> for IrqVector<'a> {
> +    type Error = Error;
> +
> +    fn try_into(self) -> Result<IrqRequest<'a>> {
> +        // SAFETY: `self.as_raw` returns a valid pointer to a `struct pci_dev`.
> +        let irq = unsafe { bindings::pci_irq_vector(self.dev.as_raw(), self.index()) };
> +        if irq < 0 {
> +            return Err(crate::error::Error::from_errno(irq));
> +        }
> +        // SAFETY: `irq` is guaranteed to be a valid IRQ number for `&self`.
> +        Ok(unsafe { IrqRequest::new(self.dev.as_ref(), irq as u32) })
> +    }
> +}
> +
>  /// Represents an IRQ vector allocation for a PCI device.
>  ///
>  /// This type ensures that IRQ vectors are properly allocated and freed by
> @@ -675,31 +689,15 @@ pub fn iomap_region<'a>(
>          self.iomap_region_sized::<0>(bar, name)
>      }
>  
> -    /// Returns an [`IrqRequest`] for the given IRQ vector.
> -    pub fn irq_vector(&self, vector: IrqVector<'_>) -> Result<IrqRequest<'_>> {
> -        // Verify that the vector belongs to this device.
> -        if !core::ptr::eq(vector.dev.as_raw(), self.as_raw()) {
> -            return Err(EINVAL);
> -        }
> -
> -        // SAFETY: `self.as_raw` returns a valid pointer to a `struct pci_dev`.
> -        let irq = unsafe { crate::bindings::pci_irq_vector(self.as_raw(), vector.index()) };
> -        if irq < 0 {
> -            return Err(crate::error::Error::from_errno(irq));
> -        }
> -        // SAFETY: `irq` is guaranteed to be a valid IRQ number for `&self`.
> -        Ok(unsafe { IrqRequest::new(self.as_ref(), irq as u32) })
> -    }
> -
>      /// Returns a [`kernel::irq::Registration`] for the given IRQ vector.
>      pub fn request_irq<'a, T: crate::irq::Handler + 'static>(
>          &'a self,
> -        vector: IrqVector<'_>,
> +        vector: IrqVector<'a>,
>          flags: irq::Flags,
>          name: &'static CStr,
>          handler: impl PinInit<T, Error> + 'a,
>      ) -> Result<impl PinInit<irq::Registration<T>, Error> + 'a> {
> -        let request = self.irq_vector(vector)?;
> +        let request = vector.try_into()?;
>  
>          Ok(irq::Registration::<T>::new(request, flags, name, handler))
>      }
> @@ -707,12 +705,12 @@ pub fn request_irq<'a, T: crate::irq::Handler + 'static>(
>      /// Returns a [`kernel::irq::ThreadedRegistration`] for the given IRQ vector.
>      pub fn request_threaded_irq<'a, T: crate::irq::ThreadedHandler + 'static>(
>          &'a self,
> -        vector: IrqVector<'_>,
> +        vector: IrqVector<'a>,
>          flags: irq::Flags,
>          name: &'static CStr,
>          handler: impl PinInit<T, Error> + 'a,
>      ) -> Result<impl PinInit<irq::ThreadedRegistration<T>, Error> + 'a> {
> -        let request = self.irq_vector(vector)?;
> +        let request = vector.try_into()?;

The resulting change to the lifetime semantics is curious, but seems
right.

Reviewed-by: Alice Ryhl <aliceryhl@...gle.com>