PCI/MSI: Introduce pci_msix_table_size()

Introduce new function pci_msix_table_size() returning the size of
the MSI-X table of given PCI device or 0 if the device doesn't
support MSI-X.
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Reviewed-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>

drivers/pci/msi.c

@@ -674,6 +674,23 @@ static int msi_free_irqs(struct pci_dev* dev)
 	return 0;
 }
 
+/**
+ * pci_msix_table_size - return the number of device's MSI-X table entries
+ * @dev: pointer to the pci_dev data structure of MSI-X device function
+ */
+int pci_msix_table_size(struct pci_dev *dev)
+{
+	int pos;
+	u16 control;
+
+	pos = pci_find_capability(dev, PCI_CAP_ID_MSIX);
+	if (!pos)
+		return 0;
+
+	pci_read_config_word(dev, msi_control_reg(pos), &control);
+	return multi_msix_capable(control);
+}
+
 /**
  * pci_enable_msix - configure device's MSI-X capability structure
  * @dev: pointer to the pci_dev data structure of MSI-X device function
@@ -691,9 +708,8 @@ static int msi_free_irqs(struct pci_dev* dev)
  **/
 int pci_enable_msix(struct pci_dev* dev, struct msix_entry *entries, int nvec)
 {
-	int status, pos, nr_entries;
+	int status, nr_entries;
 	int i, j;
-	u16 control;
 
 	if (!entries)
  		return -EINVAL;
@@ -702,9 +718,7 @@ int pci_enable_msix(struct pci_dev* dev, struct msix_entry *entries, int nvec)
 	if (status)
 		return status;
 
-	pos = pci_find_capability(dev, PCI_CAP_ID_MSIX);
-	pci_read_config_word(dev, msi_control_reg(pos), &control);
-	nr_entries = multi_msix_capable(control);
+	nr_entries = pci_msix_table_size(dev);
 	if (nvec > nr_entries)
 		return -EINVAL;
 

include/linux/pci.h

@@ -799,6 +799,10 @@ static inline void pci_msi_shutdown(struct pci_dev *dev)
 static inline void pci_disable_msi(struct pci_dev *dev)
 { }
 
+static inline int pci_msix_table_size(struct pci_dev *dev)
+{
+	return 0;
+}
 static inline int pci_enable_msix(struct pci_dev *dev,
 				  struct msix_entry *entries, int nvec)
 {
@@ -823,6 +827,7 @@ static inline int pci_msi_enabled(void)
 extern int pci_enable_msi(struct pci_dev *dev);
 extern void pci_msi_shutdown(struct pci_dev *dev);
 extern void pci_disable_msi(struct pci_dev *dev);
+extern int pci_msix_table_size(struct pci_dev *dev);
 extern int pci_enable_msix(struct pci_dev *dev,
 	struct msix_entry *entries, int nvec);
 extern void pci_msix_shutdown(struct pci_dev *dev);