PCI: Add pci_find_next_ext_capability()

Some extended capabilities, e.g., the vendor-specific capability, can
occur several times.  The existing pci_find_ext_capability() only finds
the first occurrence.  This adds pci_find_next_ext_capability(), which
can iterate through all of them.

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

drivers/pci/pci.c

@@ -285,6 +285,58 @@ static int pci_pcie_cap2(struct pci_dev *dev)
 	return pos;
 }
 
+/**
+ * pci_find_next_ext_capability - Find an extended capability
+ * @dev: PCI device to query
+ * @start: address at which to start looking (0 to start at beginning of list)
+ * @cap: capability code
+ *
+ * Returns the address of the next matching extended capability structure
+ * within the device's PCI configuration space or 0 if the device does
+ * not support it.  Some capabilities can occur several times, e.g., the
+ * vendor-specific capability, and this provides a way to find them all.
+ */
+int pci_find_next_ext_capability(struct pci_dev *dev, int start, int cap)
+{
+	u32 header;
+	int ttl;
+	int pos = PCI_CFG_SPACE_SIZE;
+
+	/* minimum 8 bytes per capability */
+	ttl = (PCI_CFG_SPACE_EXP_SIZE - PCI_CFG_SPACE_SIZE) / 8;
+
+	if (dev->cfg_size <= PCI_CFG_SPACE_SIZE)
+		return 0;
+
+	if (start)
+		pos = start;
+
+	if (pci_read_config_dword(dev, pos, &header) != PCIBIOS_SUCCESSFUL)
+		return 0;
+
+	/*
+	 * If we have no capabilities, this is indicated by cap ID,
+	 * cap version and next pointer all being 0.
+	 */
+	if (header == 0)
+		return 0;
+
+	while (ttl-- > 0) {
+		if (PCI_EXT_CAP_ID(header) == cap && pos != start)
+			return pos;
+
+		pos = PCI_EXT_CAP_NEXT(header);
+		if (pos < PCI_CFG_SPACE_SIZE)
+			break;
+
+		if (pci_read_config_dword(dev, pos, &header) != PCIBIOS_SUCCESSFUL)
+			break;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(pci_find_next_ext_capability);
+
 /**
  * pci_find_ext_capability - Find an extended capability
  * @dev: PCI device to query
@@ -301,39 +353,7 @@ static int pci_pcie_cap2(struct pci_dev *dev)
  */
 int pci_find_ext_capability(struct pci_dev *dev, int cap)
 {
-	u32 header;
+	return pci_find_next_ext_capability(dev, 0, cap);
-	int ttl;
-	int pos = PCI_CFG_SPACE_SIZE;
-
-	/* minimum 8 bytes per capability */
-	ttl = (PCI_CFG_SPACE_EXP_SIZE - PCI_CFG_SPACE_SIZE) / 8;
-
-	if (dev->cfg_size <= PCI_CFG_SPACE_SIZE)
-		return 0;
-
-	if (pci_read_config_dword(dev, pos, &header) != PCIBIOS_SUCCESSFUL)
-		return 0;
-
-	/*
-	 * If we have no capabilities, this is indicated by cap ID,
-	 * cap version and next pointer all being 0.
-	 */
-	if (header == 0)
-		return 0;
-
-	while (ttl-- > 0) {
-		if (PCI_EXT_CAP_ID(header) == cap)
-			return pos;
-
-		pos = PCI_EXT_CAP_NEXT(header);
-		if (pos < PCI_CFG_SPACE_SIZE)
-			break;
-
-		if (pci_read_config_dword(dev, pos, &header) != PCIBIOS_SUCCESSFUL)
-			break;
-	}
-
-	return 0;
 }
 EXPORT_SYMBOL_GPL(pci_find_ext_capability);
 

include/linux/pci.h

@@ -755,6 +755,7 @@ enum pci_lost_interrupt_reason pci_lost_interrupt(struct pci_dev *dev);
 int pci_find_capability(struct pci_dev *dev, int cap);
 int pci_find_next_capability(struct pci_dev *dev, u8 pos, int cap);
 int pci_find_ext_capability(struct pci_dev *dev, int cap);
+int pci_find_next_ext_capability(struct pci_dev *dev, int pos, int cap);
 int pci_find_ht_capability(struct pci_dev *dev, int ht_cap);
 int pci_find_next_ht_capability(struct pci_dev *dev, int pos, int ht_cap);
 struct pci_bus *pci_find_next_bus(const struct pci_bus *from);