PCI/MSI: Move pci_irq_get_affinity() to api.c

To disentangle the maze in msi.c, all exported device-driver MSI APIs are
now to be grouped in one file, api.c.

Move pci_irq_get_affinity() and let its kernel-doc match rest of the
file.
Signed-off-by: Ahmed S. Darwish <darwi@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Link: https://lore.kernel.org/r/20221111122015.214792769@linutronix.de

drivers/pci/msi/api.c

@@ -9,6 +9,7 @@
  */
 
 #include <linux/export.h>
+#include <linux/irq.h>
 
 #include "msi.h"
 
@@ -250,6 +251,48 @@ int pci_irq_vector(struct pci_dev *dev, unsigned int nr)
 }
 EXPORT_SYMBOL(pci_irq_vector);
 
+/**
+ * pci_irq_get_affinity() - Get a device interrupt vector affinity
+ * @dev: the PCI device to operate on
+ * @nr:  device-relative interrupt vector index (0-based); has different
+ *       meanings, depending on interrupt mode
+ *         MSI-X        the index in the MSI-X vector table
+ *         MSI          the index of the enabled MSI vectors
+ *         INTx         must be 0
+ *
+ * Return: MSI/MSI-X vector affinity, NULL if @nr is out of range or if
+ * the MSI(-X) vector was allocated without explicit affinity
+ * requirements (e.g., by pci_enable_msi(), pci_enable_msix_range(), or
+ * pci_alloc_irq_vectors() without the %PCI_IRQ_AFFINITY flag). Return a
+ * generic set of CPU IDs representing all possible CPUs available
+ * during system boot if the device is in legacy INTx mode.
+ */
+const struct cpumask *pci_irq_get_affinity(struct pci_dev *dev, int nr)
+{
+	int idx, irq = pci_irq_vector(dev, nr);
+	struct msi_desc *desc;
+
+	if (WARN_ON_ONCE(irq <= 0))
+		return NULL;
+
+	desc = irq_get_msi_desc(irq);
+	/* Non-MSI does not have the information handy */
+	if (!desc)
+		return cpu_possible_mask;
+
+	/* MSI[X] interrupts can be allocated without affinity descriptor */
+	if (!desc->affinity)
+		return NULL;
+
+	/*
+	 * MSI has a mask array in the descriptor.
+	 * MSI-X has a single mask.
+	 */
+	idx = dev->msi_enabled ? nr : 0;
+	return &desc->affinity[idx].mask;
+}
+EXPORT_SYMBOL(pci_irq_get_affinity);
+
 /**
  * pci_free_irq_vectors() - Free previously allocated IRQs for a device
  * @dev: the PCI device to operate on

drivers/pci/msi/msi.c

@@ -854,44 +854,6 @@ int __pci_enable_msix_range(struct pci_dev *dev,
 	}
 }
 
-/**
- * pci_irq_get_affinity - return the affinity of a particular MSI vector
- * @dev:	PCI device to operate on
- * @nr:		device-relative interrupt vector index (0-based).
- *
- * @nr has the following meanings depending on the interrupt mode:
- *   MSI-X:	The index in the MSI-X vector table
- *   MSI:	The index of the enabled MSI vectors
- *   INTx:	Must be 0
- *
- * Return: A cpumask pointer or NULL if @nr is out of range
- */
-const struct cpumask *pci_irq_get_affinity(struct pci_dev *dev, int nr)
-{
-	int idx, irq = pci_irq_vector(dev, nr);
-	struct msi_desc *desc;
-
-	if (WARN_ON_ONCE(irq <= 0))
-		return NULL;
-
-	desc = irq_get_msi_desc(irq);
-	/* Non-MSI does not have the information handy */
-	if (!desc)
-		return cpu_possible_mask;
-
-	/* MSI[X] interrupts can be allocated without affinity descriptor */
-	if (!desc->affinity)
-		return NULL;
-
-	/*
-	 * MSI has a mask array in the descriptor.
-	 * MSI-X has a single mask.
-	 */
-	idx = dev->msi_enabled ? nr : 0;
-	return &desc->affinity[idx].mask;
-}
-EXPORT_SYMBOL(pci_irq_get_affinity);
-
 struct pci_dev *msi_desc_to_pci_dev(struct msi_desc *desc)
 {
 	return to_pci_dev(desc->dev);