diff --git a/drivers/of/of_pci.c b/drivers/of/of_pci.c
index 13e37e2..0dd52df 100644
--- a/drivers/of/of_pci.c
+++ b/drivers/of/of_pci.c
@@ -7,12 +7,13 @@
 static inline int __of_pci_pci_compare(struct device_node *node,
 				       unsigned int devfn)
 {
-	unsigned int size;
-	const __be32 *reg = of_get_property(node, "reg", &size);
+	int err;
 
-	if (!reg || size < 5 * sizeof(__be32))
+	err = of_pci_get_devfn(node);
+	if (err < 0)
 		return 0;
-	return ((be32_to_cpup(&reg[0]) >> 8) & 0xff) == devfn;
+
+	return devfn == err;
 }
 
 struct device_node *of_pci_find_child_device(struct device_node *parent,
@@ -40,3 +41,26 @@ struct device_node *of_pci_find_child_device(struct device_node *parent,
 	return NULL;
 }
 EXPORT_SYMBOL_GPL(of_pci_find_child_device);
+
+/**
+ * of_pci_get_devfn() - Get device and function numbers for a device node
+ * @np: device node
+ *
+ * Parses a standard 5-cell PCI resource and returns an 8-bit value that can
+ * be passed to the PCI_SLOT() and PCI_FUNC() macros to extract the device
+ * and function numbers respectively. On error a negative error code is
+ * returned.
+ */
+int of_pci_get_devfn(struct device_node *np)
+{
+	unsigned int size;
+	const __be32 *reg;
+
+	reg = of_get_property(np, "reg", &size);
+
+	if (!reg || size < 5 * sizeof(__be32))
+		return -EINVAL;
+
+	return (be32_to_cpup(reg) >> 8) & 0xff;
+}
+EXPORT_SYMBOL_GPL(of_pci_get_devfn);
diff --git a/include/linux/of_pci.h b/include/linux/of_pci.h
index bb115de..91ec484 100644
--- a/include/linux/of_pci.h
+++ b/include/linux/of_pci.h
@@ -10,5 +10,6 @@ int of_irq_map_pci(const struct pci_dev *pdev, struct of_irq *out_irq);
 struct device_node;
 struct device_node *of_pci_find_child_device(struct device_node *parent,
 					     unsigned int devfn);
+int of_pci_get_devfn(struct device_node *np);
 
 #endif