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

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Message-ID: <9643ecf3-7f55-4f4b-9e5c-26c2608fb4d3@nvidia.com>
Date: Thu, 16 Oct 2025 19:02:37 -0400
From: Joel Fernandes <joelagnelf@...dia.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,
 aliceryhl@...gle.com, 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 10/16/2025 6:57 PM, Danilo Krummrich wrote:
> On Fri Oct 17, 2025 at 12:24 AM CEST, Joel Fernandes wrote:
>> 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) })
>>> +    }
>>> +}A
>>
>>
>> Nice change, looks good to me but I do feel it is odd to 'convert' an
>> IrqVector directly into a IrqRequest using TryInto (one is a device-relative
>> vector index and the other holds the notion of an IRQ request).
>>
>> Instead, we should convert IrqVector into something like LinuxIrqNumber
>> (using TryInto) because we're converting one number to another, and then pass
>> that to a separate function to create the IrqRequest.
> 
> Well, IrqRequest is exactly that, a representation of an IRQ number. So, this is
> already doing exactly that, converting one number to another:
> 
> 	pub struct IrqRequest<'a> {
> 	    dev: &'a Device<Bound>,
> 	    irq: u32,
> 	}
> 
> (The reason this is called IrqRequest instead of IrqNumber is that the number is
> an irrelevant implementation detail of how an IRQ is requested.)
> 
> 	pub struct IrqVector<'a> {
> 	    dev: &'a Device<Bound>,
> 	    index: u32,
> 	}
> 
> So, what happens here is that we convert the vector index from IrqVector into
> the irq number in IrqRequest.
Ah true, I think the naming "IrqRequest" throw me off. Sorry about that, so this
patch is good then :) Thanks,

 - Joel