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>

2 files changed, 24 insertions, 5 deletions

diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
index baba2eb5367d..08aedd5875b0 100644
--- a/drivers/pci/msi.c
+++ b/drivers/pci/msi.c
@@ -675,6 +675,23 @@ static int msi_free_irqs(struct pci_dev* dev)
 }
 
 /**
+ * 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
  * @entries: pointer to an array of MSI-X entries
@@ -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;
 
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 7bd624bfdcfd..b5d6d0e0f1cb 100644
--- a/include/linux/pci.h
+++ b/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);