of/pci: Add of_pci_parse_bus_range() function

This function can be used to parse a bus-range property as specified by
device nodes representing PCI bridges.

Signed-off-by: Thierry Reding <[e-mail]>
Signed-off-by: Jason Cooper <[e-mail]>

drivers/of/of_pci.c

···
 	return (be32_to_cpup(reg) >> 8) & 0xff;
 }
 EXPORT_SYMBOL_GPL(of_pci_get_devfn);
+
+/**
+ * of_pci_parse_bus_range() - parse the bus-range property of a PCI device
+ * @node: device node
+ * @res: address to a struct resource to return the bus-range
+ *
+ * Returns 0 on success or a negative error-code on failure.
+ */
+int of_pci_parse_bus_range(struct device_node *node, struct resource *res)
+{
+	const __be32 *values;
+	int len;
+
+	values = of_get_property(node, "bus-range", &len);
+	if (!values || len < sizeof(*values) * 2)
+		return -EINVAL;
+
+	res->name = node->name;
+	res->start = be32_to_cpup(values++);
+	res->end = be32_to_cpup(values);
+	res->flags = IORESOURCE_BUS;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(of_pci_parse_bus_range);

include/linux/of_pci.h

···
 struct device_node *of_pci_find_child_device(struct device_node *parent,
 					     unsigned int devfn);
 int of_pci_get_devfn(struct device_node *np);
+int of_pci_parse_bus_range(struct device_node *node, struct resource *res);
 
 #endif