#include <linux/kernel.h>

  #include <linux/export.h>

  #include <linux/of.h>

  #include <linux/of_pci.h>
  #include <asm/prom.h>

  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);

  	if (!reg || size < 5 * sizeof(__be32))
  		return 0;
  	return ((be32_to_cpup(&reg[0]) >> 8) & 0xff) == devfn;
  }

  struct device_node *of_pci_find_child_device(struct device_node *parent,
  					     unsigned int devfn)
  {
  	struct device_node *node, *node2;
  
  	for_each_child_of_node(parent, node) {
  		if (__of_pci_pci_compare(node, devfn))
  			return node;
  		/*
  		 * Some OFs create a parent node "multifunc-device" as
  		 * a fake root for all functions of a multi-function
  		 * device we go down them as well.

  		 */

  		if (!strcmp(node->name, "multifunc-device")) {
  			for_each_child_of_node(node, node2) {
  				if (__of_pci_pci_compare(node2, devfn)) {
  					of_node_put(node);
  					return node2;
  				}
  			}
  		}

  	}

  	return NULL;

  }

  EXPORT_SYMBOL_GPL(of_pci_find_child_device);