rust: pci: add irq accessors

These accessors can be used to retrieve a irq::Registration or a
irq::ThreadedRegistration from a pci device. Alternatively, drivers can
retrieve an IrqRequest from a bound PCI device for later use.

These accessors ensure that only valid IRQ lines can ever be registered.

Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Tested-by: Joel Fernandes <joelagnelf@nvidia.com>
Tested-by: Dirk Behme <dirk.behme@de.bosch.com>
Signed-off-by: Daniel Almeida <daniel.almeida@collabora.com>
Link: https://lore.kernel.org/r/20250811-topics-tyr-request_irq2-v9-6-0485dcd9bcbf@collabora.com
Signed-off-by: Danilo Krummrich <dakr@kernel.org>

rust/helpers/pci.c

@@ -11,3 +11,11 @@ bool rust_helper_dev_is_pci(const struct device *dev)
 {
 	return dev_is_pci(dev);
 }
+
+#ifndef CONFIG_PCI_MSI
+int rust_helper_pci_irq_vector(struct pci_dev *pdev, unsigned int nvec)
+{
+	return pci_irq_vector(pdev, nvec);
+}
+
+#endif

rust/kernel/pci.rs

@@ -10,8 +10,8 @@
     devres::Devres,
     driver,
     error::{from_result, to_result, Result},
-    io::Io,
-    io::IoRaw,
+    io::{Io, IoRaw},
+    irq::{self, IrqRequest},
     str::CStr,
     types::{ARef, Opaque},
     ThisModule,
@@ -431,6 +431,47 @@ pub fn iomap_region<'a>(
     ) -> impl PinInit<Devres<Bar>, Error> + 'a {
         self.iomap_region_sized::<0>(bar, name)
     }
+
+    /// Returns an [`IrqRequest`] for the IRQ vector at the given index, if any.
+    pub fn irq_vector(&self, index: u32) -> Result<IrqRequest<'_>> {
+        // SAFETY: `self.as_raw` returns a valid pointer to a `struct pci_dev`.
+        let irq = unsafe { crate::bindings::pci_irq_vector(self.as_raw(), 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 IRQ vector at the given
+    /// index.
+    pub fn request_irq<'a, T: crate::irq::Handler + 'static>(
+        &'a self,
+        index: u32,
+        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(index)?;
+
+        Ok(irq::Registration::<T>::new(request, flags, name, handler))
+    }
+
+    /// Returns a [`kernel::irq::ThreadedRegistration`] for the IRQ vector at
+    /// the given index.
+    pub fn request_threaded_irq<'a, T: crate::irq::ThreadedHandler + 'static>(
+        &'a self,
+        index: u32,
+        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(index)?;
+
+        Ok(irq::ThreadedRegistration::<T>::new(
+            request, flags, name, handler,
+        ))
+    }
 }
 
 impl Device<device::Core> {