PCI/MSI: Add pci_msix_vec_count()

This creates an MSI-X counterpart for pci_msi_vec_count().  Device drivers
can use this function to obtain maximum number of MSI-X interrupts the
device supports and use that number in a subsequent call to
pci_enable_msix().

pci_msix_vec_count() supersedes pci_msix_table_size() and returns a
negative errno if device does not support MSI-X interrupts.  After this
update, callers must always check the returned value.

The only user of pci_msix_table_size() was the PCI-Express port driver,
which is also updated by this change.

Signed-off-by: Alexander Gordeev <agordeev@redhat.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Tejun Heo <tj@kernel.org>

1 files changed, 13 insertions, 5 deletions

diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
index 76507ab..bd18ecf 100644
--- a/drivers/pci/msi.c
+++ b/drivers/pci/msi.c
@@ -948,19 +948,25 @@ void pci_disable_msi(struct pci_dev *dev)
 EXPORT_SYMBOL(pci_disable_msi);
 
 /**
- * pci_msix_table_size - return the number of device's MSI-X table entries
+ * pci_msix_vec_count - 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)
+
+ * This function returns the number of device's MSI-X table entries and
+ * therefore the number of MSI-X vectors device is capable of sending.
+ * It returns a negative errno if the device is not capable of sending MSI-X
+ * interrupts.
+ **/
+int pci_msix_vec_count(struct pci_dev *dev)
 {
 	u16 control;
 
 	if (!dev->msix_cap)
-		return 0;
+		return -EINVAL;
 
 	pci_read_config_word(dev, dev->msix_cap + PCI_MSIX_FLAGS, &control);
 	return msix_table_size(control);
 }
+EXPORT_SYMBOL(pci_msix_vec_count);
 
 /**
  * pci_enable_msix - configure device's MSI-X capability structure
@@ -989,7 +995,9 @@ int pci_enable_msix(struct pci_dev *dev, struct msix_entry *entries, int nvec)
 	if (status)
 		return status;
 
-	nr_entries = pci_msix_table_size(dev);
+	nr_entries = pci_msix_vec_count(dev);
+	if (nr_entries < 0)
+		return nr_entries;
 	if (nvec > nr_entries)
 		return nr_entries;