Re: [PATCH v2] rust: pci: Allocate and manage PCI interrupt vectors

[Joel Fernandes <joelagnelf@nvidia.com>]

On 10/5/2025 8:56 AM, Danilo Krummrich wrote:
>> +        let ret = unsafe {
>> +            bindings::pci_alloc_irq_vectors(dev.as_raw(), min_vecs, max_vecs, irq_types.as_raw())
>> +        };
>> +
>> +        to_result(ret)?;
>> +        let count = ret as u32;
>> +
>> +        // SAFETY: Vectors are 0-based, so valid indices are [0, count-1].
>> +        // pci_alloc_irq_vectors guarantees count >= min_vecs > 0, so count - 1 is valid.
>> This is a justification why the range makes sense (which makes sense to keep as
> a separate comment), but it doesn't justify the safety requirement of
> IrqVector::new().

Is the following better? Or did you have some other reasoning you want me to
mention? The safety comes from the fact that both start/end vector indices and
everything in between are valid.

// SAFETY:
// - `pci_alloc_irq_vectors` returns the number of allocated vectors on success.
// - Vectors are 0-based, so valid indices are [0, count-1].
// - `pci_alloc_irq_vectors` guarantees count >= min_vecs > 0, so both 0 and
//    count - 1 are valid IRQ vector indices for device `dev`.
// - Vector indices are contiguous, so all vectors in [0, count-1] are valid.

Thanks.