Danilo Krummrich
2025-Sep-15 09:48 UTC
[PATCH] rust: pci: add PCI interrupt allocation and management support
On Wed Sep 10, 2025 at 9:02 PM CEST, Joel Fernandes wrote:> On Wed, Sep 10, 2025 at 02:09:55PM -0400, Joel Fernandes wrote: > [...] >> > > + /// Allocate IRQ vectors for this PCI device. >> > > + /// >> > > + /// Allocates between `min_vecs` and `max_vecs` interrupt vectors for the device. >> > > + /// The allocation will use MSI-X, MSI, or legacy interrupts based on the `irq_types` >> > > + /// parameter and hardware capabilities. When multiple types are specified, the kernel >> > > + /// will try them in order of preference: MSI-X first, then MSI, then legacy interrupts. >> > > + /// This is called during driver probe. >> > > + /// >> > > + /// # Arguments >> > > + /// >> > > + /// * `min_vecs` - Minimum number of vectors required >> > > + /// * `max_vecs` - Maximum number of vectors to allocate >> > > + /// * `irq_types` - Types of interrupts that can be used >> > > + /// >> > > + /// # Returns >> > > + /// >> > > + /// Returns the number of vectors successfully allocated, or an error if the allocation >> > > + /// fails or cannot meet the minimum requirement. >> > > + /// >> > > + /// # Examples >> > > + /// >> > > + /// ``` >> > > + /// // Allocate using any available interrupt type in the order mentioned above. >> > > + /// let nvecs = dev.alloc_irq_vectors(1, 32, IrqTypes::all())?; >> > > + /// >> > > + /// // Allocate MSI or MSI-X only (no legacy interrupts) >> > > + /// let msi_only = IrqTypes::default() >> > > + /// .with(IrqType::Msi) >> > > + /// .with(IrqType::MsiX); >> > > + /// let nvecs = dev.alloc_irq_vectors(4, 16, msi_only)?; >> > > + /// ``` >> > > + pub fn alloc_irq_vectors( >> > > + &self, >> > > + min_vecs: u32, >> > > + max_vecs: u32, >> > > + irq_types: IrqTypes, >> > > + ) -> Result<u32> { >> > > + // SAFETY: `self.as_raw` is guaranteed to be a pointer to a valid `struct pci_dev`. >> > > + // `pci_alloc_irq_vectors` internally validates all parameters and returns error codes. >> > > + let ret = unsafe { >> > > + bindings::pci_alloc_irq_vectors(self.as_raw(), min_vecs, max_vecs, irq_types.raw()) >> > > + }; >> > > + >> > > + to_result(ret)?; >> > > + Ok(ret as u32) >> > > + } >> > >> > This is only valid to be called from the Core context, as it modifies internal >> > fields of the inner struct device. >> >> It is called from core context, the diff format confuses. >> > >> > Also, it would be nice if it would return a new type that can serve as argument >> > for irq_vector(), such that we don't have to rely on random integers. >> >> Makes sense, I will do that. >> > By the way, the "ret" value returned by pci_alloc_irq_vectors() is the number > of vectors, not the vector index.Sure, but the vector index passed to pci_irq_vector() must be in the range defined by the return value of pci_alloc_irq_vectors(). I thought of e.g. Range<pci::IrqVector> as return value. This way you can easily iterate it and prove that it's an allocated vector index.> So basically there are 3 numbers that mean > different things: > 1. Number of vectors (as returned by alloc_irq_vectors). > 2. Index of a vector (passed to pci_irq_vector). > 3. The Linux IRQ number (passed to request_irq). > > And your point is well taken, in fact even in current code there is > ambiguity: irq_vector() accepts a vector index, where as request_irq() > accepts a Linux IRQ number, which are different numbers. I can try to clean > that up as well but let me know if you had any other thoughts. In fact, I > think Device<device::Bound>::request_irq() pci should just accept IrqRequest?Currently, pci::Device::request_irq() takes an IRQ vector index and calls irq_vector() internally to convert the vector index into an IRQ number. I'd keep this semantics, but introduce a new type IrqVector rather than using the raw integer. So, drivers would call // `irq_vecs` is of type `Range<pci::IrqVector>`. let irq_vecs = dev.alloc_irq_vectors(1, 1, pci::IrqTypes::ANY)?; let irq = KBox::pin_init( dev.request_irq(irq_vecs.start, ...)?, )?; Alternatively, to request all of them, if we have multiple, we can leverage KBox::pin_slice(), which will land in v6.18 (see alloc-next or rust-next branch in the Rust tree), so all irq::Registration objects can be stored in a single allocation.