[PATCH v2 4/5] PCI: Add pci_irq_type() to query the allocated interrupt type

[Danilo Krummrich <dakr@kernel.org>]

Add a helper that returns PCI_IRQ_MSIX, PCI_IRQ_MSI, or PCI_IRQ_INTX
based on the interrupt type the PCI core selected after
pci_alloc_irq_vectors().

Several drivers already open-code this check against pdev->msix_enabled
and pdev->msi_enabled, or even open code this helper [1].

A common helper avoids the duplication and keeps drivers from accessing
the bitfield directly (see also [2]).

Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Link: https://elixir.bootlin.com/linux/v7.1/source/drivers/net/ethernet/aquantia/atlantic/aq_pci_func.c#L196 [1]
Inspired-by: John Hubbard <jhubbard@nvidia.com>
Link: https://lore.kernel.org/all/DKKG2QM3YJYB.Z2H2B2UXJ75N@kernel.org/ [2]
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
---
 include/linux/pci.h | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/include/linux/pci.h b/include/linux/pci.h
index 64b308b6e61c..80b8561b5be0 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -1783,6 +1783,26 @@ void pci_free_irq_vectors(struct pci_dev *dev);
 int pci_irq_vector(struct pci_dev *dev, unsigned int nr);
 const struct cpumask *pci_irq_get_affinity(struct pci_dev *pdev, int vec);
 
+/**
+ * pci_irq_type - Get the interrupt type of a PCI device
+ * @pdev: the PCI device to operate on
+ *
+ * Discriminate the interrupt type the PCI core selected for this device
+ * after a successful pci_alloc_irq_vectors() call.
+ *
+ * Return: %PCI_IRQ_MSIX, %PCI_IRQ_MSI, or %PCI_IRQ_INTX.
+ */
+static inline unsigned int pci_irq_type(struct pci_dev *pdev)
+{
+	if (pdev->msix_enabled)
+		return PCI_IRQ_MSIX;
+
+	if (pdev->msi_enabled)
+		return PCI_IRQ_MSI;
+
+	return PCI_IRQ_INTX;
+}
+
 #else
 static inline int pci_msi_vec_count(struct pci_dev *dev) { return -ENOSYS; }
 static inline void pci_disable_msi(struct pci_dev *dev) { }
@@ -1845,6 +1865,11 @@ static inline const struct cpumask *pci_irq_get_affinity(struct pci_dev *pdev,
 {
 	return cpu_possible_mask;
 }
+
+static inline unsigned int pci_irq_type(struct pci_dev *pdev)
+{
+	return PCI_IRQ_INTX;
+}
 #endif
 
 /**
-- 
2.55.0