PCI/MSI: Move pci_enable_msi() API 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_enable_msi() and make its kernel-doc comprehensive.
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/20221111122014.755178149@linutronix.de

drivers/pci/msi/api.c

@@ -12,6 +12,29 @@
 
 #include "msi.h"
 
+/**
+ * pci_enable_msi() - Enable MSI interrupt mode on device
+ * @dev: the PCI device to operate on
+ *
+ * Legacy device driver API to enable MSI interrupts mode on device and
+ * allocate a single interrupt vector. On success, the allocated vector
+ * Linux IRQ will be saved at @dev->irq. The driver must invoke
+ * pci_disable_msi() on cleanup.
+ *
+ * NOTE: The newer pci_alloc_irq_vectors() / pci_free_irq_vectors() API
+ * pair should, in general, be used instead.
+ *
+ * Return: 0 on success, errno otherwise
+ */
+int pci_enable_msi(struct pci_dev *dev)
+{
+	int rc = __pci_enable_msi_range(dev, 1, 1, NULL);
+	if (rc < 0)
+		return rc;
+	return 0;
+}
+EXPORT_SYMBOL(pci_enable_msi);
+
 /**
  * pci_disable_msi() - Disable MSI interrupt mode on device
  * @dev: the PCI device to operate on

drivers/pci/msi/msi.c

@@ -790,8 +790,8 @@ void pci_disable_msix(struct pci_dev *dev)
 }
 EXPORT_SYMBOL(pci_disable_msix);
 
-static int __pci_enable_msi_range(struct pci_dev *dev, int minvec, int maxvec,
-				  struct irq_affinity *affd)
+int __pci_enable_msi_range(struct pci_dev *dev, int minvec, int maxvec,
+			   struct irq_affinity *affd)
 {
 	int nvec;
 	int rc;
@@ -844,16 +844,6 @@ static int __pci_enable_msi_range(struct pci_dev *dev, int minvec, int maxvec,
 	}
 }
 
-/* deprecated, don't use */
-int pci_enable_msi(struct pci_dev *dev)
-{
-	int rc = __pci_enable_msi_range(dev, 1, 1, NULL);
-	if (rc < 0)
-		return rc;
-	return 0;
-}
-EXPORT_SYMBOL(pci_enable_msi);
-
 static int __pci_enable_msix_range(struct pci_dev *dev,
 				   struct msix_entry *entries, int minvec,
 				   int maxvec, struct irq_affinity *affd,

drivers/pci/msi/msi.h

@@ -87,6 +87,7 @@ static inline __attribute_const__ u32 msi_multi_mask(struct msi_desc *desc)
 /* MSI internal functions invoked from the public APIs */
 void pci_msi_shutdown(struct pci_dev *dev);
 void pci_free_msi_irqs(struct pci_dev *dev);
+int __pci_enable_msi_range(struct pci_dev *dev, int minvec, int maxvec, struct irq_affinity *affd);
 
 /* Legacy (!IRQDOMAIN) fallbacks */
 #ifdef CONFIG_PCI_MSI_ARCH_FALLBACKS