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>

1 files changed, 30 insertions, 10 deletions

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index f3ea977a5b1b..d34415ba0f64 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -286,20 +286,17 @@ static int pci_pcie_cap2(struct pci_dev *dev)
 }
 
 /**
- * pci_find_ext_capability - Find an extended capability
+ * 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 requested extended capability structure
+ * 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.  Possible values for @cap:
- *
- *  %PCI_EXT_CAP_ID_ERR         Advanced Error Reporting
- *  %PCI_EXT_CAP_ID_VC          Virtual Channel
- *  %PCI_EXT_CAP_ID_DSN         Device Serial Number
- *  %PCI_EXT_CAP_ID_PWR         Power Budgeting
+ * 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_ext_capability(struct pci_dev *dev, int cap)
+int pci_find_next_ext_capability(struct pci_dev *dev, int start, int cap)
 {
         u32 header;
         int ttl;
@@ -311,6 +308,9 @@ int pci_find_ext_capability(struct pci_dev *dev, int cap)
         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;
 
@@ -322,7 +322,7 @@ int pci_find_ext_capability(struct pci_dev *dev, int cap)
                 return 0;
 
         while (ttl-- > 0) {
-                if (PCI_EXT_CAP_ID(header) == cap)
+                if (PCI_EXT_CAP_ID(header) == cap && pos != start)
                         return pos;
 
                 pos = PCI_EXT_CAP_NEXT(header);
@@ -335,6 +335,26 @@ int pci_find_ext_capability(struct pci_dev *dev, int cap)
 
         return 0;
 }
+EXPORT_SYMBOL_GPL(pci_find_next_ext_capability);
+
+/**
+ * pci_find_ext_capability - Find an extended capability
+ * @dev: PCI device to query
+ * @cap: capability code
+ *
+ * Returns the address of the requested extended capability structure
+ * within the device's PCI configuration space or 0 if the device does
+ * not support it.  Possible values for @cap:
+ *
+ *  %PCI_EXT_CAP_ID_ERR         Advanced Error Reporting
+ *  %PCI_EXT_CAP_ID_VC          Virtual Channel
+ *  %PCI_EXT_CAP_ID_DSN         Device Serial Number
+ *  %PCI_EXT_CAP_ID_PWR         Power Budgeting
+ */
+int pci_find_ext_capability(struct pci_dev *dev, int cap)
+{
+        return pci_find_next_ext_capability(dev, 0, cap);
+}
 EXPORT_SYMBOL_GPL(pci_find_ext_capability);
 
 static int __pci_find_next_ht_cap(struct pci_dev *dev, int pos, int ht_cap)