/*
   * Procedures for creating, accessing and interpreting the device tree.
   *
   * Paul Mackerras	August 1996.
   * Copyright (C) 1996-2005 Paul Mackerras.
   *
   *  Adapted for 64bit PowerPC by Dave Engebretsen and Peter Bergner.
   *    {engebret|bergner}@us.ibm.com
   *
   *  Adapted for sparc and sparc64 by David S. Miller davem@davemloft.net
   *

   *  Reconsolidated from arch/x/kernel/prom.c by Stephen Rothwell and
   *  Grant Likely.

   *
   *      This program is free software; you can redistribute it and/or
   *      modify it under the terms of the GNU General Public License
   *      as published by the Free Software Foundation; either version
   *      2 of the License, or (at your option) any later version.
   */
  #include <linux/module.h>
  #include <linux/of.h>

  #include <linux/spinlock.h>

  #include <linux/slab.h>

  #include <linux/proc_fs.h>

  struct device_node *allnodes;

  struct device_node *of_chosen;

  /* use when traversing tree through the allnext, child, sibling,
   * or parent members of struct device_node.
   */
  DEFINE_RWLOCK(devtree_lock);

  
  int of_n_addr_cells(struct device_node *np)
  {

  	const __be32 *ip;

  
  	do {
  		if (np->parent)
  			np = np->parent;
  		ip = of_get_property(np, "#address-cells", NULL);
  		if (ip)

  			return be32_to_cpup(ip);

  	} while (np->parent);
  	/* No #address-cells property for the root node */
  	return OF_ROOT_NODE_ADDR_CELLS_DEFAULT;
  }
  EXPORT_SYMBOL(of_n_addr_cells);
  
  int of_n_size_cells(struct device_node *np)
  {

  	const __be32 *ip;

  
  	do {
  		if (np->parent)
  			np = np->parent;
  		ip = of_get_property(np, "#size-cells", NULL);
  		if (ip)

  			return be32_to_cpup(ip);

  	} while (np->parent);
  	/* No #size-cells property for the root node */
  	return OF_ROOT_NODE_SIZE_CELLS_DEFAULT;
  }
  EXPORT_SYMBOL(of_n_size_cells);

  #if !defined(CONFIG_SPARC)   /* SPARC doesn't do ref counting (yet) */
  /**
   *	of_node_get - Increment refcount of a node
   *	@node:	Node to inc refcount, NULL is supported to
   *		simplify writing of callers
   *
   *	Returns node.
   */
  struct device_node *of_node_get(struct device_node *node)
  {
  	if (node)
  		kref_get(&node->kref);
  	return node;
  }
  EXPORT_SYMBOL(of_node_get);
  
  static inline struct device_node *kref_to_device_node(struct kref *kref)
  {
  	return container_of(kref, struct device_node, kref);
  }
  
  /**
   *	of_node_release - release a dynamically allocated node
   *	@kref:  kref element of the node to be released
   *
   *	In of_node_put() this function is passed to kref_put()
   *	as the destructor.
   */
  static void of_node_release(struct kref *kref)
  {
  	struct device_node *node = kref_to_device_node(kref);
  	struct property *prop = node->properties;
  
  	/* We should never be releasing nodes that haven't been detached. */
  	if (!of_node_check_flag(node, OF_DETACHED)) {
  		pr_err("ERROR: Bad of_node_put() on %s
  ", node->full_name);
  		dump_stack();
  		kref_init(&node->kref);
  		return;
  	}
  
  	if (!of_node_check_flag(node, OF_DYNAMIC))
  		return;
  
  	while (prop) {
  		struct property *next = prop->next;
  		kfree(prop->name);
  		kfree(prop->value);
  		kfree(prop);
  		prop = next;
  
  		if (!prop) {
  			prop = node->deadprops;
  			node->deadprops = NULL;
  		}
  	}
  	kfree(node->full_name);
  	kfree(node->data);
  	kfree(node);
  }
  
  /**
   *	of_node_put - Decrement refcount of a node
   *	@node:	Node to dec refcount, NULL is supported to
   *		simplify writing of callers
   *
   */
  void of_node_put(struct device_node *node)
  {
  	if (node)
  		kref_put(&node->kref, of_node_release);
  }
  EXPORT_SYMBOL(of_node_put);
  #endif /* !CONFIG_SPARC */

  struct property *of_find_property(const struct device_node *np,
  				  const char *name,
  				  int *lenp)
  {
  	struct property *pp;

  	if (!np)
  		return NULL;

  	read_lock(&devtree_lock);
  	for (pp = np->properties; pp != 0; pp = pp->next) {
  		if (of_prop_cmp(pp->name, name) == 0) {
  			if (lenp != 0)
  				*lenp = pp->length;
  			break;
  		}
  	}
  	read_unlock(&devtree_lock);
  
  	return pp;
  }
  EXPORT_SYMBOL(of_find_property);

  /**
   * of_find_all_nodes - Get next node in global list
   * @prev:	Previous node or NULL to start iteration
   *		of_node_put() will be called on it
   *
   * Returns a node pointer with refcount incremented, use
   * of_node_put() on it when done.
   */
  struct device_node *of_find_all_nodes(struct device_node *prev)
  {
  	struct device_node *np;
  
  	read_lock(&devtree_lock);
  	np = prev ? prev->allnext : allnodes;
  	for (; np != NULL; np = np->allnext)
  		if (of_node_get(np))
  			break;
  	of_node_put(prev);
  	read_unlock(&devtree_lock);
  	return np;
  }
  EXPORT_SYMBOL(of_find_all_nodes);

  /*
   * Find a property with a given name for a given node
   * and return the value.
   */
  const void *of_get_property(const struct device_node *np, const char *name,
  			 int *lenp)
  {
  	struct property *pp = of_find_property(np, name, lenp);
  
  	return pp ? pp->value : NULL;
  }
  EXPORT_SYMBOL(of_get_property);

  
  /** Checks if the given "compat" string matches one of the strings in
   * the device's "compatible" property
   */
  int of_device_is_compatible(const struct device_node *device,
  		const char *compat)
  {
  	const char* cp;
  	int cplen, l;
  
  	cp = of_get_property(device, "compatible", &cplen);
  	if (cp == NULL)
  		return 0;
  	while (cplen > 0) {
  		if (of_compat_cmp(cp, compat, strlen(compat)) == 0)
  			return 1;
  		l = strlen(cp) + 1;
  		cp += l;
  		cplen -= l;
  	}
  
  	return 0;
  }
  EXPORT_SYMBOL(of_device_is_compatible);

  
  /**

   * of_machine_is_compatible - Test root of device tree for a given compatible value

   * @compat: compatible string to look for in root node's compatible property.
   *
   * Returns true if the root node has the given value in its
   * compatible property.
   */

  int of_machine_is_compatible(const char *compat)

  {
  	struct device_node *root;
  	int rc = 0;
  
  	root = of_find_node_by_path("/");
  	if (root) {
  		rc = of_device_is_compatible(root, compat);
  		of_node_put(root);
  	}
  	return rc;
  }

  EXPORT_SYMBOL(of_machine_is_compatible);

  
  /**

   *  of_device_is_available - check if a device is available for use
   *
   *  @device: Node to check for availability
   *
   *  Returns 1 if the status property is absent or set to "okay" or "ok",
   *  0 otherwise
   */
  int of_device_is_available(const struct device_node *device)
  {
  	const char *status;
  	int statlen;
  
  	status = of_get_property(device, "status", &statlen);
  	if (status == NULL)
  		return 1;
  
  	if (statlen > 0) {
  		if (!strcmp(status, "okay") || !strcmp(status, "ok"))
  			return 1;
  	}
  
  	return 0;
  }
  EXPORT_SYMBOL(of_device_is_available);
  
  /**

   *	of_get_parent - Get a node's parent if any
   *	@node:	Node to get parent
   *
   *	Returns a node pointer with refcount incremented, use
   *	of_node_put() on it when done.
   */
  struct device_node *of_get_parent(const struct device_node *node)
  {
  	struct device_node *np;
  
  	if (!node)
  		return NULL;
  
  	read_lock(&devtree_lock);
  	np = of_node_get(node->parent);
  	read_unlock(&devtree_lock);
  	return np;
  }
  EXPORT_SYMBOL(of_get_parent);

  
  /**

   *	of_get_next_parent - Iterate to a node's parent
   *	@node:	Node to get parent of
   *
   * 	This is like of_get_parent() except that it drops the
   * 	refcount on the passed node, making it suitable for iterating
   * 	through a node's parents.
   *
   *	Returns a node pointer with refcount incremented, use
   *	of_node_put() on it when done.
   */
  struct device_node *of_get_next_parent(struct device_node *node)
  {
  	struct device_node *parent;
  
  	if (!node)
  		return NULL;
  
  	read_lock(&devtree_lock);
  	parent = of_node_get(node->parent);
  	of_node_put(node);
  	read_unlock(&devtree_lock);
  	return parent;
  }
  
  /**

   *	of_get_next_child - Iterate a node childs
   *	@node:	parent node
   *	@prev:	previous child of the parent node, or NULL to get first
   *
   *	Returns a node pointer with refcount incremented, use
   *	of_node_put() on it when done.
   */
  struct device_node *of_get_next_child(const struct device_node *node,
  	struct device_node *prev)
  {
  	struct device_node *next;
  
  	read_lock(&devtree_lock);
  	next = prev ? prev->sibling : node->child;
  	for (; next; next = next->sibling)
  		if (of_node_get(next))
  			break;
  	of_node_put(prev);
  	read_unlock(&devtree_lock);
  	return next;
  }
  EXPORT_SYMBOL(of_get_next_child);

  
  /**
   *	of_find_node_by_path - Find a node matching a full OF path
   *	@path:	The full path to match
   *
   *	Returns a node pointer with refcount incremented, use
   *	of_node_put() on it when done.
   */
  struct device_node *of_find_node_by_path(const char *path)
  {
  	struct device_node *np = allnodes;
  
  	read_lock(&devtree_lock);
  	for (; np; np = np->allnext) {
  		if (np->full_name && (of_node_cmp(np->full_name, path) == 0)
  		    && of_node_get(np))
  			break;
  	}
  	read_unlock(&devtree_lock);
  	return np;
  }
  EXPORT_SYMBOL(of_find_node_by_path);
  
  /**
   *	of_find_node_by_name - Find a node by its "name" property
   *	@from:	The node to start searching from or NULL, the node
   *		you pass will not be searched, only the next one
   *		will; typically, you pass what the previous call
   *		returned. of_node_put() will be called on it
   *	@name:	The name string to match against
   *
   *	Returns a node pointer with refcount incremented, use
   *	of_node_put() on it when done.
   */
  struct device_node *of_find_node_by_name(struct device_node *from,
  	const char *name)
  {
  	struct device_node *np;
  
  	read_lock(&devtree_lock);
  	np = from ? from->allnext : allnodes;
  	for (; np; np = np->allnext)
  		if (np->name && (of_node_cmp(np->name, name) == 0)
  		    && of_node_get(np))
  			break;
  	of_node_put(from);
  	read_unlock(&devtree_lock);
  	return np;
  }
  EXPORT_SYMBOL(of_find_node_by_name);
  
  /**
   *	of_find_node_by_type - Find a node by its "device_type" property
   *	@from:	The node to start searching from, or NULL to start searching
   *		the entire device tree. The node you pass will not be
   *		searched, only the next one will; typically, you pass
   *		what the previous call returned. of_node_put() will be
   *		called on from for you.
   *	@type:	The type string to match against
   *
   *	Returns a node pointer with refcount incremented, use
   *	of_node_put() on it when done.
   */
  struct device_node *of_find_node_by_type(struct device_node *from,
  	const char *type)
  {
  	struct device_node *np;
  
  	read_lock(&devtree_lock);
  	np = from ? from->allnext : allnodes;
  	for (; np; np = np->allnext)
  		if (np->type && (of_node_cmp(np->type, type) == 0)
  		    && of_node_get(np))
  			break;
  	of_node_put(from);
  	read_unlock(&devtree_lock);
  	return np;
  }
  EXPORT_SYMBOL(of_find_node_by_type);
  
  /**
   *	of_find_compatible_node - Find a node based on type and one of the
   *                                tokens in its "compatible" property
   *	@from:		The node to start searching from or NULL, the node
   *			you pass will not be searched, only the next one
   *			will; typically, you pass what the previous call
   *			returned. of_node_put() will be called on it
   *	@type:		The type string to match "device_type" or NULL to ignore
   *	@compatible:	The string to match to one of the tokens in the device
   *			"compatible" list.
   *
   *	Returns a node pointer with refcount incremented, use
   *	of_node_put() on it when done.
   */
  struct device_node *of_find_compatible_node(struct device_node *from,
  	const char *type, const char *compatible)
  {
  	struct device_node *np;
  
  	read_lock(&devtree_lock);
  	np = from ? from->allnext : allnodes;
  	for (; np; np = np->allnext) {
  		if (type
  		    && !(np->type && (of_node_cmp(np->type, type) == 0)))
  			continue;
  		if (of_device_is_compatible(np, compatible) && of_node_get(np))
  			break;
  	}
  	of_node_put(from);
  	read_unlock(&devtree_lock);
  	return np;
  }
  EXPORT_SYMBOL(of_find_compatible_node);

  
  /**

   *	of_find_node_with_property - Find a node which has a property with
   *                                   the given name.
   *	@from:		The node to start searching from or NULL, the node
   *			you pass will not be searched, only the next one
   *			will; typically, you pass what the previous call
   *			returned. of_node_put() will be called on it
   *	@prop_name:	The name of the property to look for.
   *
   *	Returns a node pointer with refcount incremented, use
   *	of_node_put() on it when done.
   */
  struct device_node *of_find_node_with_property(struct device_node *from,
  	const char *prop_name)
  {
  	struct device_node *np;
  	struct property *pp;
  
  	read_lock(&devtree_lock);
  	np = from ? from->allnext : allnodes;
  	for (; np; np = np->allnext) {
  		for (pp = np->properties; pp != 0; pp = pp->next) {
  			if (of_prop_cmp(pp->name, prop_name) == 0) {
  				of_node_get(np);
  				goto out;
  			}
  		}
  	}
  out:
  	of_node_put(from);
  	read_unlock(&devtree_lock);
  	return np;
  }
  EXPORT_SYMBOL(of_find_node_with_property);
  
  /**

   * of_match_node - Tell if an device_node has a matching of_match structure
   *	@matches:	array of of device match structures to search in
   *	@node:		the of device structure to match against
   *
   *	Low level utility function used by device matching.
   */
  const struct of_device_id *of_match_node(const struct of_device_id *matches,
  					 const struct device_node *node)
  {

  	if (!matches)
  		return NULL;

  	while (matches->name[0] || matches->type[0] || matches->compatible[0]) {
  		int match = 1;
  		if (matches->name[0])
  			match &= node->name
  				&& !strcmp(matches->name, node->name);
  		if (matches->type[0])
  			match &= node->type
  				&& !strcmp(matches->type, node->type);
  		if (matches->compatible[0])
  			match &= of_device_is_compatible(node,
  						matches->compatible);
  		if (match)
  			return matches;
  		matches++;
  	}
  	return NULL;
  }
  EXPORT_SYMBOL(of_match_node);
  
  /**
   *	of_find_matching_node - Find a node based on an of_device_id match
   *				table.
   *	@from:		The node to start searching from or NULL, the node
   *			you pass will not be searched, only the next one
   *			will; typically, you pass what the previous call
   *			returned. of_node_put() will be called on it
   *	@matches:	array of of device match structures to search in
   *
   *	Returns a node pointer with refcount incremented, use
   *	of_node_put() on it when done.
   */
  struct device_node *of_find_matching_node(struct device_node *from,
  					  const struct of_device_id *matches)
  {
  	struct device_node *np;
  
  	read_lock(&devtree_lock);
  	np = from ? from->allnext : allnodes;
  	for (; np; np = np->allnext) {
  		if (of_match_node(matches, np) && of_node_get(np))
  			break;
  	}
  	of_node_put(from);
  	read_unlock(&devtree_lock);
  	return np;
  }
  EXPORT_SYMBOL(of_find_matching_node);

  
  /**

   * of_modalias_node - Lookup appropriate modalias for a device node
   * @node:	pointer to a device tree node
   * @modalias:	Pointer to buffer that modalias value will be copied into
   * @len:	Length of modalias value
   *

   * Based on the value of the compatible property, this routine will attempt
   * to choose an appropriate modalias value for a particular device tree node.
   * It does this by stripping the manufacturer prefix (as delimited by a ',')
   * from the first entry in the compatible list property.

   *

   * This routine returns 0 on success, <0 on failure.

   */
  int of_modalias_node(struct device_node *node, char *modalias, int len)
  {

  	const char *compatible, *p;
  	int cplen;

  
  	compatible = of_get_property(node, "compatible", &cplen);

  	if (!compatible || strlen(compatible) > cplen)

  		return -ENODEV;

  	p = strchr(compatible, ',');

  	strlcpy(modalias, p ? p + 1 : compatible, len);

  	return 0;
  }
  EXPORT_SYMBOL_GPL(of_modalias_node);

  /**

   * of_find_node_by_phandle - Find a node given a phandle
   * @handle:	phandle of the node to find
   *
   * Returns a node pointer with refcount incremented, use
   * of_node_put() on it when done.
   */
  struct device_node *of_find_node_by_phandle(phandle handle)
  {
  	struct device_node *np;
  
  	read_lock(&devtree_lock);
  	for (np = allnodes; np; np = np->allnext)
  		if (np->phandle == handle)
  			break;
  	of_node_get(np);
  	read_unlock(&devtree_lock);
  	return np;
  }
  EXPORT_SYMBOL(of_find_node_by_phandle);
  
  /**

   * of_parse_phandle - Resolve a phandle property to a device_node pointer
   * @np: Pointer to device node holding phandle property
   * @phandle_name: Name of property holding a phandle value
   * @index: For properties holding a table of phandles, this is the index into
   *         the table
   *
   * Returns the device_node pointer with refcount incremented.  Use
   * of_node_put() on it when done.
   */
  struct device_node *
  of_parse_phandle(struct device_node *np, const char *phandle_name, int index)
  {

  	const __be32 *phandle;

  	int size;
  
  	phandle = of_get_property(np, phandle_name, &size);
  	if ((!phandle) || (size < sizeof(*phandle) * (index + 1)))
  		return NULL;

  	return of_find_node_by_phandle(be32_to_cpup(phandle + index));

  }
  EXPORT_SYMBOL(of_parse_phandle);
  
  /**

   * of_parse_phandles_with_args - Find a node pointed by phandle in a list
   * @np:		pointer to a device tree node containing a list
   * @list_name:	property name that contains a list
   * @cells_name:	property name that specifies phandles' arguments count
   * @index:	index of a phandle to parse out

   * @out_node:	optional pointer to device_node struct pointer (will be filled)
   * @out_args:	optional pointer to arguments pointer (will be filled)

   *
   * This function is useful to parse lists of phandles and their arguments.
   * Returns 0 on success and fills out_node and out_args, on error returns
   * appropriate errno value.
   *
   * Example:
   *
   * phandle1: node1 {
   * 	#list-cells = <2>;
   * }
   *
   * phandle2: node2 {
   * 	#list-cells = <1>;
   * }
   *
   * node3 {
   * 	list = <&phandle1 1 2 &phandle2 3>;
   * }
   *
   * To get a device_node of the `node2' node you may call this:
   * of_parse_phandles_with_args(node3, "list", "#list-cells", 2, &node2, &args);
   */
  int of_parse_phandles_with_args(struct device_node *np, const char *list_name,
  				const char *cells_name, int index,
  				struct device_node **out_node,
  				const void **out_args)
  {
  	int ret = -EINVAL;

  	const __be32 *list;
  	const __be32 *list_end;

  	int size;
  	int cur_index = 0;
  	struct device_node *node = NULL;

  	const void *args = NULL;

  
  	list = of_get_property(np, list_name, &size);
  	if (!list) {
  		ret = -ENOENT;
  		goto err0;
  	}
  	list_end = list + size / sizeof(*list);
  
  	while (list < list_end) {

  		const __be32 *cells;

  		phandle phandle;

  		phandle = be32_to_cpup(list++);

  		args = list;

  
  		/* one cell hole in the list = <>; */

  		if (!phandle)

  			goto next;

  		node = of_find_node_by_phandle(phandle);

  		if (!node) {
  			pr_debug("%s: could not find phandle
  ",
  				 np->full_name);
  			goto err0;
  		}
  
  		cells = of_get_property(node, cells_name, &size);
  		if (!cells || size != sizeof(*cells)) {
  			pr_debug("%s: could not get %s for %s
  ",
  				 np->full_name, cells_name, node->full_name);
  			goto err1;
  		}

  		list += be32_to_cpup(cells);

  		if (list > list_end) {
  			pr_debug("%s: insufficient arguments length
  ",
  				 np->full_name);
  			goto err1;
  		}
  next:
  		if (cur_index == index)
  			break;
  
  		of_node_put(node);
  		node = NULL;

  		args = NULL;

  		cur_index++;
  	}
  
  	if (!node) {

  		/*
  		 * args w/o node indicates that the loop above has stopped at
  		 * the 'hole' cell. Report this differently.
  		 */
  		if (args)
  			ret = -EEXIST;
  		else
  			ret = -ENOENT;

  		goto err0;
  	}

  	if (out_node)
  		*out_node = node;
  	if (out_args)
  		*out_args = args;

  
  	return 0;
  err1:
  	of_node_put(node);
  err0:
  	pr_debug("%s failed with status %d
  ", __func__, ret);
  	return ret;
  }
  EXPORT_SYMBOL(of_parse_phandles_with_args);

  
  /**
   * prom_add_property - Add a property to a node
   */
  int prom_add_property(struct device_node *np, struct property *prop)
  {
  	struct property **next;
  	unsigned long flags;
  
  	prop->next = NULL;
  	write_lock_irqsave(&devtree_lock, flags);
  	next = &np->properties;
  	while (*next) {
  		if (strcmp(prop->name, (*next)->name) == 0) {
  			/* duplicate ! don't insert it */
  			write_unlock_irqrestore(&devtree_lock, flags);
  			return -1;
  		}
  		next = &(*next)->next;
  	}
  	*next = prop;
  	write_unlock_irqrestore(&devtree_lock, flags);
  
  #ifdef CONFIG_PROC_DEVICETREE
  	/* try to add to proc as well if it was initialized */
  	if (np->pde)
  		proc_device_tree_add_prop(np->pde, prop);
  #endif /* CONFIG_PROC_DEVICETREE */
  
  	return 0;
  }
  
  /**
   * prom_remove_property - Remove a property from a node.
   *
   * Note that we don't actually remove it, since we have given out
   * who-knows-how-many pointers to the data using get-property.
   * Instead we just move the property to the "dead properties"
   * list, so it won't be found any more.
   */
  int prom_remove_property(struct device_node *np, struct property *prop)
  {
  	struct property **next;
  	unsigned long flags;
  	int found = 0;
  
  	write_lock_irqsave(&devtree_lock, flags);
  	next = &np->properties;
  	while (*next) {
  		if (*next == prop) {
  			/* found the node */
  			*next = prop->next;
  			prop->next = np->deadprops;
  			np->deadprops = prop;
  			found = 1;
  			break;
  		}
  		next = &(*next)->next;
  	}
  	write_unlock_irqrestore(&devtree_lock, flags);
  
  	if (!found)
  		return -ENODEV;
  
  #ifdef CONFIG_PROC_DEVICETREE
  	/* try to remove the proc node as well */
  	if (np->pde)
  		proc_device_tree_remove_prop(np->pde, prop);
  #endif /* CONFIG_PROC_DEVICETREE */
  
  	return 0;
  }
  
  /*
   * prom_update_property - Update a property in a node.
   *
   * Note that we don't actually remove it, since we have given out
   * who-knows-how-many pointers to the data using get-property.
   * Instead we just move the property to the "dead properties" list,
   * and add the new property to the property list
   */
  int prom_update_property(struct device_node *np,
  			 struct property *newprop,
  			 struct property *oldprop)
  {
  	struct property **next;
  	unsigned long flags;
  	int found = 0;
  
  	write_lock_irqsave(&devtree_lock, flags);
  	next = &np->properties;
  	while (*next) {
  		if (*next == oldprop) {
  			/* found the node */
  			newprop->next = oldprop->next;
  			*next = newprop;
  			oldprop->next = np->deadprops;
  			np->deadprops = oldprop;
  			found = 1;
  			break;
  		}
  		next = &(*next)->next;
  	}
  	write_unlock_irqrestore(&devtree_lock, flags);
  
  	if (!found)
  		return -ENODEV;
  
  #ifdef CONFIG_PROC_DEVICETREE
  	/* try to add to proc as well if it was initialized */
  	if (np->pde)
  		proc_device_tree_update_prop(np->pde, newprop, oldprop);
  #endif /* CONFIG_PROC_DEVICETREE */
  
  	return 0;
  }

  
  #if defined(CONFIG_OF_DYNAMIC)
  /*
   * Support for dynamic device trees.
   *
   * On some platforms, the device tree can be manipulated at runtime.
   * The routines in this section support adding, removing and changing
   * device tree nodes.
   */
  
  /**
   * of_attach_node - Plug a device node into the tree and global list.
   */
  void of_attach_node(struct device_node *np)
  {
  	unsigned long flags;
  
  	write_lock_irqsave(&devtree_lock, flags);
  	np->sibling = np->parent->child;
  	np->allnext = allnodes;
  	np->parent->child = np;
  	allnodes = np;
  	write_unlock_irqrestore(&devtree_lock, flags);
  }
  
  /**
   * of_detach_node - "Unplug" a node from the device tree.
   *
   * The caller must hold a reference to the node.  The memory associated with
   * the node is not freed until its refcount goes to zero.
   */
  void of_detach_node(struct device_node *np)
  {
  	struct device_node *parent;
  	unsigned long flags;
  
  	write_lock_irqsave(&devtree_lock, flags);
  
  	parent = np->parent;
  	if (!parent)
  		goto out_unlock;
  
  	if (allnodes == np)
  		allnodes = np->allnext;
  	else {
  		struct device_node *prev;
  		for (prev = allnodes;
  		     prev->allnext != np;
  		     prev = prev->allnext)
  			;
  		prev->allnext = np->allnext;
  	}
  
  	if (parent->child == np)
  		parent->child = np->sibling;
  	else {
  		struct device_node *prevsib;
  		for (prevsib = np->parent->child;
  		     prevsib->sibling != np;
  		     prevsib = prevsib->sibling)
  			;
  		prevsib->sibling = np->sibling;
  	}
  
  	of_node_set_flag(np, OF_DETACHED);
  
  out_unlock:
  	write_unlock_irqrestore(&devtree_lock, flags);
  }
  #endif /* defined(CONFIG_OF_DYNAMIC) */