PCI: Add pci_bus_find_ext_capability
For use by code that needs to walk extended capability lists before
pci_dev structures are set up.
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
LKML-Reference: <43F901BD926A4E43B106BF17856F07559FB80CFD@orsmsx508.amr.corp.intel.com>
Signed-off-by: Jacob Pan <jacob.jun.pan@intel.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 315fea4..aad62af 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -297,6 +297,49 @@
}
EXPORT_SYMBOL_GPL(pci_find_ext_capability);
+/**
+ * pci_bus_find_ext_capability - find an extended capability
+ * @bus: the PCI bus to query
+ * @devfn: PCI device to query
+ * @cap: capability code
+ *
+ * Like pci_find_ext_capability() but works for pci devices that do not have a
+ * pci_dev structure set up yet.
+ *
+ * Returns the address of the requested capability structure within the
+ * device's PCI configuration space or 0 in case the device does not
+ * support it.
+ */
+int pci_bus_find_ext_capability(struct pci_bus *bus, unsigned int devfn,
+ 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 (!pci_bus_read_config_dword(bus, devfn, pos, &header))
+ return 0;
+ if (header == 0xffffffff || 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_bus_read_config_dword(bus, devfn, pos, &header))
+ break;
+ }
+
+ return 0;
+}
+
static int __pci_find_next_ht_cap(struct pci_dev *dev, int pos, int ht_cap)
{
int rc, ttl = PCI_FIND_CAP_TTL;