PCI/MSI: Simplify pci_irq_get_affinity()

Replace open coded MSI descriptor chasing and use the proper accessor
functions instead.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Michael Kelley <mikelley@microsoft.com>
Tested-by: Nishanth Menon <nm@ti.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/20211210221814.900929381@linutronix.de

drivers/pci/msi/msi.c

@@ -1104,26 +1104,20 @@ EXPORT_SYMBOL(pci_irq_vector);
  */
 const struct cpumask *pci_irq_get_affinity(struct pci_dev *dev, int nr)
 {
-	if (dev->msix_enabled) {
-		struct msi_desc *entry;
-
-		for_each_pci_msi_entry(entry, dev) {
-			if (entry->msi_index == nr)
-				return &entry->affinity->mask;
-		}
-		WARN_ON_ONCE(1);
-		return NULL;
-	} else if (dev->msi_enabled) {
-		struct msi_desc *entry = first_pci_msi_entry(dev);
+	int irq = pci_irq_vector(dev, nr);
+	struct msi_desc *desc;
 
-		if (WARN_ON_ONCE(!entry || !entry->affinity ||
-				 nr >= entry->nvec_used))
+	if (WARN_ON_ONCE(irq <= 0))
 		return NULL;
 
-		return &entry->affinity[nr].mask;
-	} else {
+	desc = irq_get_msi_desc(irq);
+	/* Non-MSI does not have the information handy */
+	if (!desc)
 		return cpu_possible_mask;
-	}
+
+	if (WARN_ON_ONCE(!desc->affinity))
+		return NULL;
+	return &desc->affinity[nr].mask;
 }
 EXPORT_SYMBOL(pci_irq_get_affinity);