[PATCH 1/3] pci: Add PCI walk function and PCIe bridge test

[Alex Williamson <alex.williamson-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>]

These will replace pci_find_upstream_pcie_bridge, which is difficult
to use and rather specific to intel-iommu usage.  A quirked
pci_is_pcie_bridge function is provided to work around non-compliant
PCIe-to-PCI bridges such as those found in
https://bugzilla.kernel.org/show_bug.cgi?id=44881

Signed-off-by: Alex Williamson <alex.williamson-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
---
 drivers/pci/search.c |   57 ++++++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/pci.h  |   23 ++++++++++++++++++++
 2 files changed, 80 insertions(+)

diff --git a/drivers/pci/search.c b/drivers/pci/search.c
index d0627fa..0357f74 100644
--- a/drivers/pci/search.c
+++ b/drivers/pci/search.c
@@ -17,6 +17,63 @@
 DECLARE_RWSEM(pci_bus_sem);
 EXPORT_SYMBOL_GPL(pci_bus_sem);
 
+/* Test for PCIe bridges. */
+bool pci_is_pcie_bridge(struct pci_dev *pdev)
+{
+	if (!pci_is_bridge(pdev))
+		return false;
+
+	if (pci_is_pcie(pdev))
+		return true;
+
+#ifdef CONFIG_PCI_QUIRKS
+	/*
+	 * If we're not on the root bus, look one device upstream of the
+	 * current device.  If that device is PCIe and is not a PCIe-to-PCI
+	 * bridge, then the current device is effectively PCIe as it must
+	 * be the PCIe-to-PCI bridge.  This handles several bridges that
+	 * violate the PCIe spec by not exposing a PCIe capability:
+	 * https://bugzilla.kernel.org/show_bug.cgi?id=44881
+	 */
+	if (!pci_is_root_bus(pdev->bus)) {
+		struct pci_dev *parent = pdev->bus->self;
+
+		if (pci_is_pcie(parent) &&
+		    pci_pcie_type(parent) != PCI_EXP_TYPE_PCI_BRIDGE)
+
+			return true;
+	}
+#endif
+	return false;
+}
+
+/*
+ * Walk upstream from the given pdev for the first device returning
+ * true for the provided match function.  If no match is found, return
+ * NULL.  *last records the previous step in the walk.
+ */
+struct pci_dev *pci_walk_up_to_first_match(struct pci_dev *pdev,
+					   bool (*match)(struct pci_dev *),
+					   struct pci_dev **last)
+{
+	*last = NULL;
+
+	if (match(pdev))
+		return pdev;
+
+	*last = pdev;
+
+	while (!pci_is_root_bus(pdev->bus)) {
+		*last = pdev;
+		pdev = pdev->bus->self;
+
+		if (match(pdev))
+			return pdev;
+	}
+
+	return NULL;
+}
+
 /*
  * find the upstream PCIe-to-PCI bridge of a PCI device
  * if the device is PCIE, return NULL
diff --git a/include/linux/pci.h b/include/linux/pci.h
index bd8ec30..e87423a 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -1855,6 +1855,29 @@ static inline struct eeh_dev *pci_dev_to_eeh_dev(struct pci_dev *pdev)
 #endif
 
 /**
+ * pci_walk_up_to_first_match - Generic upstream search function
+ * @pdev: starting PCI device to search
+ * @match: match function to call on each device (true = match)
+ * @last: last device examined prior to returned device
+ *
+ * Walk upstream from the given device, calling match() at each device.
+ * Returns the first device matching match().  If the root bus is reached
+ * without finding a match, return NULL.  last returns the N-1 step in
+ * the search path.
+ */
+struct pci_dev *pci_walk_up_to_first_match(struct pci_dev *pdev,
+					   bool (*match)(struct pci_dev *),
+					   struct pci_dev **last);
+
+/**
+ * pci_is_pcie_bridge - Match a PCIe bridge device
+ * @pdev: device to test
+ *
+ * Return true if the given device is a PCIe bridge, false otherwise.
+ */
+bool pci_is_pcie_bridge(struct pci_dev *pdev);
+
+/**
  * pci_find_upstream_pcie_bridge - find upstream PCIe-to-PCI bridge of a device
  * @pdev: the PCI device
  *