PCI: Make the "entries" argument to pci_enable_msix() optional

The "entries" argument isn't needed if the list of entries does not contain
any holes.  Make it optional so that we can avoid the need to allocate a
msix_entry structure for this (common) case.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Alexander Gordeev <agordeev@redhat.com>

drivers/pci/msi.c

@@ -695,7 +695,10 @@ static int msix_setup_entries(struct pci_dev *dev, void __iomem *base,
 
 		entry->msi_attrib.is_msix	= 1;
 		entry->msi_attrib.is_64		= 1;
+		if (entries)
 			entry->msi_attrib.entry_nr = entries[i].entry;
+		else
+			entry->msi_attrib.entry_nr = i;
 		entry->msi_attrib.default_irq	= dev->irq;
 		entry->mask_base		= base;
 		entry->nvec_used		= 1;
@@ -713,11 +716,11 @@ static void msix_program_entries(struct pci_dev *dev,
 	int i = 0;
 
 	for_each_pci_msi_entry(entry, dev) {
-		entries[i].vector = entry->irq;
+		if (entries)
+			entries[i++].vector = entry->irq;
 		entry->masked = readl(pci_msix_desc_addr(entry) +
 				PCI_MSIX_ENTRY_VECTOR_CTRL);
 		msix_mask_irq(entry, 1);
-		i++;
 	}
 }
 
@@ -930,7 +933,7 @@ EXPORT_SYMBOL(pci_msix_vec_count);
 /**
  * pci_enable_msix - configure device's MSI-X capability structure
  * @dev: pointer to the pci_dev data structure of MSI-X device function
- * @entries: pointer to an array of MSI-X entries
+ * @entries: pointer to an array of MSI-X entries (optional)
  * @nvec: number of MSI-X irqs requested for allocation by device driver
  *
  * Setup the MSI-X capability structure of device function with the number
@@ -950,15 +953,13 @@ int pci_enable_msix(struct pci_dev *dev, struct msix_entry *entries, int nvec)
 	if (!pci_msi_supported(dev, nvec))
 		return -EINVAL;
 
-	if (!entries)
-		return -EINVAL;
-
 	nr_entries = pci_msix_vec_count(dev);
 	if (nr_entries < 0)
 		return nr_entries;
 	if (nvec > nr_entries)
 		return nr_entries;
 
+	if (entries) {
 		/* Check for any invalid entries */
 		for (i = 0; i < nvec; i++) {
 			if (entries[i].entry >= nr_entries)
@@ -968,6 +969,7 @@ int pci_enable_msix(struct pci_dev *dev, struct msix_entry *entries, int nvec)
 					return -EINVAL;	/* duplicate entry */
 			}
 		}
+	}
 	WARN_ON(!!dev->msix_enabled);
 
 	/* Check whether driver already requested for MSI irq */