/*
   * 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.
   */
  
  #include <linux/of.h>
  #include <linux/spinlock.h>
  #include <linux/slab.h>
  #include <linux/string.h>
  #include <linux/proc_fs.h>
  
  #include "of_private.h"
  
  /**
   * 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)
  		kobject_get(&node->kobj);
  	return node;
  }
  EXPORT_SYMBOL(of_node_get);
  
  /**
   * 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)
  		kobject_put(&node->kobj);
  }
  EXPORT_SYMBOL(of_node_put);
  
  void __of_detach_node_sysfs(struct device_node *np)
  {
  	struct property *pp;
  
  	if (!IS_ENABLED(CONFIG_SYSFS))
  		return;
  
  	BUG_ON(!of_node_is_initialized(np));
  	if (!of_kset)
  		return;
  
  	/* only remove properties if on sysfs */
  	if (of_node_is_attached(np)) {
  		for_each_property_of_node(np, pp)
  			__of_sysfs_remove_bin_file(np, pp);
  		kobject_del(&np->kobj);
  	}
  
  	/* finally remove the kobj_init ref */
  	of_node_put(np);
  }
  
  static BLOCKING_NOTIFIER_HEAD(of_reconfig_chain);
  
  int of_reconfig_notifier_register(struct notifier_block *nb)
  {
  	return blocking_notifier_chain_register(&of_reconfig_chain, nb);
  }
  EXPORT_SYMBOL_GPL(of_reconfig_notifier_register);
  
  int of_reconfig_notifier_unregister(struct notifier_block *nb)
  {
  	return blocking_notifier_chain_unregister(&of_reconfig_chain, nb);
  }
  EXPORT_SYMBOL_GPL(of_reconfig_notifier_unregister);
  
  #ifdef DEBUG
  const char *action_names[] = {
  	[OF_RECONFIG_ATTACH_NODE] = "ATTACH_NODE",
  	[OF_RECONFIG_DETACH_NODE] = "DETACH_NODE",
  	[OF_RECONFIG_ADD_PROPERTY] = "ADD_PROPERTY",
  	[OF_RECONFIG_REMOVE_PROPERTY] = "REMOVE_PROPERTY",
  	[OF_RECONFIG_UPDATE_PROPERTY] = "UPDATE_PROPERTY",
  };
  #endif
  
  int of_reconfig_notify(unsigned long action, struct of_reconfig_data *p)
  {
  	int rc;
  #ifdef DEBUG
  	struct of_reconfig_data *pr = p;
  
  	switch (action) {
  	case OF_RECONFIG_ATTACH_NODE:
  	case OF_RECONFIG_DETACH_NODE:
  		pr_debug("of/notify %-15s %s
  ", action_names[action],
  			pr->dn->full_name);
  		break;
  	case OF_RECONFIG_ADD_PROPERTY:
  	case OF_RECONFIG_REMOVE_PROPERTY:
  	case OF_RECONFIG_UPDATE_PROPERTY:
  		pr_debug("of/notify %-15s %s:%s
  ", action_names[action],
  			pr->dn->full_name, pr->prop->name);
  		break;
  
  	}
  #endif
  	rc = blocking_notifier_call_chain(&of_reconfig_chain, action, p);
  	return notifier_to_errno(rc);
  }
  
  /*
   * of_reconfig_get_state_change()	- Returns new state of device
   * @action	- action of the of notifier
   * @arg		- argument of the of notifier
   *
   * Returns the new state of a device based on the notifier used.
   * Returns 0 on device going from enabled to disabled, 1 on device
   * going from disabled to enabled and -1 on no change.
   */
  int of_reconfig_get_state_change(unsigned long action, struct of_reconfig_data *pr)
  {
  	struct property *prop, *old_prop = NULL;
  	int is_status, status_state, old_status_state, prev_state, new_state;
  
  	/* figure out if a device should be created or destroyed */
  	switch (action) {
  	case OF_RECONFIG_ATTACH_NODE:
  	case OF_RECONFIG_DETACH_NODE:
  		prop = of_find_property(pr->dn, "status", NULL);
  		break;
  	case OF_RECONFIG_ADD_PROPERTY:
  	case OF_RECONFIG_REMOVE_PROPERTY:
  		prop = pr->prop;
  		break;
  	case OF_RECONFIG_UPDATE_PROPERTY:
  		prop = pr->prop;
  		old_prop = pr->old_prop;
  		break;
  	default:
  		return OF_RECONFIG_NO_CHANGE;
  	}
  
  	is_status = 0;
  	status_state = -1;
  	old_status_state = -1;
  	prev_state = -1;
  	new_state = -1;
  
  	if (prop && !strcmp(prop->name, "status")) {
  		is_status = 1;
  		status_state = !strcmp(prop->value, "okay") ||
  			       !strcmp(prop->value, "ok");
  		if (old_prop)
  			old_status_state = !strcmp(old_prop->value, "okay") ||
  					   !strcmp(old_prop->value, "ok");
  	}
  
  	switch (action) {
  	case OF_RECONFIG_ATTACH_NODE:
  		prev_state = 0;
  		/* -1 & 0 status either missing or okay */
  		new_state = status_state != 0;
  		break;
  	case OF_RECONFIG_DETACH_NODE:
  		/* -1 & 0 status either missing or okay */
  		prev_state = status_state != 0;
  		new_state = 0;
  		break;
  	case OF_RECONFIG_ADD_PROPERTY:
  		if (is_status) {
  			/* no status property -> enabled (legacy) */
  			prev_state = 1;
  			new_state = status_state;
  		}
  		break;
  	case OF_RECONFIG_REMOVE_PROPERTY:
  		if (is_status) {
  			prev_state = status_state;
  			/* no status property -> enabled (legacy) */
  			new_state = 1;
  		}
  		break;
  	case OF_RECONFIG_UPDATE_PROPERTY:
  		if (is_status) {
  			prev_state = old_status_state != 0;
  			new_state = status_state != 0;
  		}
  		break;
  	}
  
  	if (prev_state == new_state)
  		return OF_RECONFIG_NO_CHANGE;
  
  	return new_state ? OF_RECONFIG_CHANGE_ADD : OF_RECONFIG_CHANGE_REMOVE;
  }
  EXPORT_SYMBOL_GPL(of_reconfig_get_state_change);
  
  int of_property_notify(int action, struct device_node *np,
  		       struct property *prop, struct property *oldprop)
  {
  	struct of_reconfig_data pr;
  
  	/* only call notifiers if the node is attached */
  	if (!of_node_is_attached(np))
  		return 0;
  
  	pr.dn = np;
  	pr.prop = prop;
  	pr.old_prop = oldprop;
  	return of_reconfig_notify(action, &pr);
  }
  
  void __of_attach_node(struct device_node *np)
  {
  	const __be32 *phandle;
  	int sz;
  
  	np->name = __of_get_property(np, "name", NULL) ? : "<NULL>";
  	np->type = __of_get_property(np, "device_type", NULL) ? : "<NULL>";
  
  	phandle = __of_get_property(np, "phandle", &sz);
  	if (!phandle)
  		phandle = __of_get_property(np, "linux,phandle", &sz);
  	if (IS_ENABLED(CONFIG_PPC_PSERIES) && !phandle)
  		phandle = __of_get_property(np, "ibm,phandle", &sz);
  	np->phandle = (phandle && (sz >= 4)) ? be32_to_cpup(phandle) : 0;
  
  	np->child = NULL;
  	np->sibling = np->parent->child;
  	np->parent->child = np;
  	of_node_clear_flag(np, OF_DETACHED);
  }
  
  /**
   * of_attach_node() - Plug a device node into the tree and global list.
   */
  int of_attach_node(struct device_node *np)
  {
  	struct of_reconfig_data rd;
  	unsigned long flags;
  
  	memset(&rd, 0, sizeof(rd));
  	rd.dn = np;
  
  	mutex_lock(&of_mutex);
  	raw_spin_lock_irqsave(&devtree_lock, flags);
  	__of_attach_node(np);
  	raw_spin_unlock_irqrestore(&devtree_lock, flags);
  
  	__of_attach_node_sysfs(np);
  	mutex_unlock(&of_mutex);
  
  	of_reconfig_notify(OF_RECONFIG_ATTACH_NODE, &rd);
  
  	return 0;
  }
  
  void __of_detach_node(struct device_node *np)
  {
  	struct device_node *parent;
  
  	if (WARN_ON(of_node_check_flag(np, OF_DETACHED)))
  		return;
  
  	parent = np->parent;
  	if (WARN_ON(!parent))
  		return;
  
  	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);
  }
  
  /**
   * 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.
   */
  int of_detach_node(struct device_node *np)
  {
  	struct of_reconfig_data rd;
  	unsigned long flags;
  	int rc = 0;
  
  	memset(&rd, 0, sizeof(rd));
  	rd.dn = np;
  
  	mutex_lock(&of_mutex);
  	raw_spin_lock_irqsave(&devtree_lock, flags);
  	__of_detach_node(np);
  	raw_spin_unlock_irqrestore(&devtree_lock, flags);
  
  	__of_detach_node_sysfs(np);
  	mutex_unlock(&of_mutex);
  
  	of_reconfig_notify(OF_RECONFIG_DETACH_NODE, &rd);
  
  	return rc;
  }
  
  /**
   * 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.
   */
  void of_node_release(struct kobject *kobj)
  {
  	struct device_node *node = kobj_to_device_node(kobj);
  	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();
  		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_prop_dup - Copy a property dynamically.
   * @prop:	Property to copy
   * @allocflags:	Allocation flags (typically pass GFP_KERNEL)
   *
   * Copy a property by dynamically allocating the memory of both the
   * property structure and the property name & contents. The property's
   * flags have the OF_DYNAMIC bit set so that we can differentiate between
   * dynamically allocated properties and not.
   * Returns the newly allocated property or NULL on out of memory error.
   */
  struct property *__of_prop_dup(const struct property *prop, gfp_t allocflags)
  {
  	struct property *new;
  
  	new = kzalloc(sizeof(*new), allocflags);
  	if (!new)
  		return NULL;
  
  	/*
  	 * NOTE: There is no check for zero length value.
  	 * In case of a boolean property, this will allocate a value
  	 * of zero bytes. We do this to work around the use
  	 * of of_get_property() calls on boolean values.
  	 */
  	new->name = kstrdup(prop->name, allocflags);
  	new->value = kmemdup(prop->value, prop->length, allocflags);
  	new->length = prop->length;
  	if (!new->name || !new->value)
  		goto err_free;
  
  	/* mark the property as dynamic */
  	of_property_set_flag(new, OF_DYNAMIC);
  
  	return new;
  
   err_free:
  	kfree(new->name);
  	kfree(new->value);
  	kfree(new);
  	return NULL;
  }
  
  /**
   * __of_node_dup() - Duplicate or create an empty device node dynamically.
   * @fmt: Format string (plus vargs) for new full name of the device node
   *
   * Create an device tree node, either by duplicating an empty node or by allocating
   * an empty one suitable for further modification.  The node data are
   * dynamically allocated and all the node flags have the OF_DYNAMIC &
   * OF_DETACHED bits set. Returns the newly allocated node or NULL on out of
   * memory error.
   */
  struct device_node *__of_node_dup(const struct device_node *np, const char *fmt, ...)
  {
  	va_list vargs;
  	struct device_node *node;
  
  	node = kzalloc(sizeof(*node), GFP_KERNEL);
  	if (!node)
  		return NULL;
  	va_start(vargs, fmt);
  	node->full_name = kvasprintf(GFP_KERNEL, fmt, vargs);
  	va_end(vargs);
  	if (!node->full_name) {
  		kfree(node);
  		return NULL;
  	}
  
  	of_node_set_flag(node, OF_DYNAMIC);
  	of_node_set_flag(node, OF_DETACHED);
  	of_node_init(node);
  
  	/* Iterate over and duplicate all properties */
  	if (np) {
  		struct property *pp, *new_pp;
  		for_each_property_of_node(np, pp) {
  			new_pp = __of_prop_dup(pp, GFP_KERNEL);
  			if (!new_pp)
  				goto err_prop;
  			if (__of_add_property(node, new_pp)) {
  				kfree(new_pp->name);
  				kfree(new_pp->value);
  				kfree(new_pp);
  				goto err_prop;
  			}
  		}
  	}
  	return node;
  
   err_prop:
  	of_node_put(node); /* Frees the node and properties */
  	return NULL;
  }
  
  static void __of_changeset_entry_destroy(struct of_changeset_entry *ce)
  {
  	of_node_put(ce->np);
  	list_del(&ce->node);
  	kfree(ce);
  }
  
  #ifdef DEBUG
  static void __of_changeset_entry_dump(struct of_changeset_entry *ce)
  {
  	switch (ce->action) {
  	case OF_RECONFIG_ADD_PROPERTY:
  	case OF_RECONFIG_REMOVE_PROPERTY:
  	case OF_RECONFIG_UPDATE_PROPERTY:
  		pr_debug("of/cset<%p> %-15s %s/%s
  ", ce, action_names[ce->action],
  			ce->np->full_name, ce->prop->name);
  		break;
  	case OF_RECONFIG_ATTACH_NODE:
  	case OF_RECONFIG_DETACH_NODE:
  		pr_debug("of/cset<%p> %-15s %s
  ", ce, action_names[ce->action],
  			ce->np->full_name);
  		break;
  	}
  }
  #else
  static inline void __of_changeset_entry_dump(struct of_changeset_entry *ce)
  {
  	/* empty */
  }
  #endif
  
  static void __of_changeset_entry_invert(struct of_changeset_entry *ce,
  					  struct of_changeset_entry *rce)
  {
  	memcpy(rce, ce, sizeof(*rce));
  
  	switch (ce->action) {
  	case OF_RECONFIG_ATTACH_NODE:
  		rce->action = OF_RECONFIG_DETACH_NODE;
  		break;
  	case OF_RECONFIG_DETACH_NODE:
  		rce->action = OF_RECONFIG_ATTACH_NODE;
  		break;
  	case OF_RECONFIG_ADD_PROPERTY:
  		rce->action = OF_RECONFIG_REMOVE_PROPERTY;
  		break;
  	case OF_RECONFIG_REMOVE_PROPERTY:
  		rce->action = OF_RECONFIG_ADD_PROPERTY;
  		break;
  	case OF_RECONFIG_UPDATE_PROPERTY:
  		rce->old_prop = ce->prop;
  		rce->prop = ce->old_prop;
  		break;
  	}
  }
  
  static void __of_changeset_entry_notify(struct of_changeset_entry *ce, bool revert)
  {
  	struct of_reconfig_data rd;
  	struct of_changeset_entry ce_inverted;
  	int ret;
  
  	if (revert) {
  		__of_changeset_entry_invert(ce, &ce_inverted);
  		ce = &ce_inverted;
  	}
  
  	switch (ce->action) {
  	case OF_RECONFIG_ATTACH_NODE:
  	case OF_RECONFIG_DETACH_NODE:
  		memset(&rd, 0, sizeof(rd));
  		rd.dn = ce->np;
  		ret = of_reconfig_notify(ce->action, &rd);
  		break;
  	case OF_RECONFIG_ADD_PROPERTY:
  	case OF_RECONFIG_REMOVE_PROPERTY:
  	case OF_RECONFIG_UPDATE_PROPERTY:
  		ret = of_property_notify(ce->action, ce->np, ce->prop, ce->old_prop);
  		break;
  	default:
  		pr_err("%s: invalid devicetree changeset action: %i
  ", __func__,
  			(int)ce->action);
  		return;
  	}
  
  	if (ret)
  		pr_err("%s: notifier error @%s
  ", __func__, ce->np->full_name);
  }
  
  static int __of_changeset_entry_apply(struct of_changeset_entry *ce)
  {
  	struct property *old_prop, **propp;
  	unsigned long flags;
  	int ret = 0;
  
  	__of_changeset_entry_dump(ce);
  
  	raw_spin_lock_irqsave(&devtree_lock, flags);
  	switch (ce->action) {
  	case OF_RECONFIG_ATTACH_NODE:
  		__of_attach_node(ce->np);
  		break;
  	case OF_RECONFIG_DETACH_NODE:
  		__of_detach_node(ce->np);
  		break;
  	case OF_RECONFIG_ADD_PROPERTY:
  		/* If the property is in deadprops then it must be removed */
  		for (propp = &ce->np->deadprops; *propp; propp = &(*propp)->next) {
  			if (*propp == ce->prop) {
  				*propp = ce->prop->next;
  				ce->prop->next = NULL;
  				break;
  			}
  		}
  
  		ret = __of_add_property(ce->np, ce->prop);
  		if (ret) {
  			pr_err("%s: add_property failed @%s/%s
  ",
  				__func__, ce->np->full_name,
  				ce->prop->name);
  			break;
  		}
  		break;
  	case OF_RECONFIG_REMOVE_PROPERTY:
  		ret = __of_remove_property(ce->np, ce->prop);
  		if (ret) {
  			pr_err("%s: remove_property failed @%s/%s
  ",
  				__func__, ce->np->full_name,
  				ce->prop->name);
  			break;
  		}
  		break;
  
  	case OF_RECONFIG_UPDATE_PROPERTY:
  		/* If the property is in deadprops then it must be removed */
  		for (propp = &ce->np->deadprops; *propp; propp = &(*propp)->next) {
  			if (*propp == ce->prop) {
  				*propp = ce->prop->next;
  				ce->prop->next = NULL;
  				break;
  			}
  		}
  
  		ret = __of_update_property(ce->np, ce->prop, &old_prop);
  		if (ret) {
  			pr_err("%s: update_property failed @%s/%s
  ",
  				__func__, ce->np->full_name,
  				ce->prop->name);
  			break;
  		}
  		break;
  	default:
  		ret = -EINVAL;
  	}
  	raw_spin_unlock_irqrestore(&devtree_lock, flags);
  
  	if (ret)
  		return ret;
  
  	switch (ce->action) {
  	case OF_RECONFIG_ATTACH_NODE:
  		__of_attach_node_sysfs(ce->np);
  		break;
  	case OF_RECONFIG_DETACH_NODE:
  		__of_detach_node_sysfs(ce->np);
  		break;
  	case OF_RECONFIG_ADD_PROPERTY:
  		/* ignore duplicate names */
  		__of_add_property_sysfs(ce->np, ce->prop);
  		break;
  	case OF_RECONFIG_REMOVE_PROPERTY:
  		__of_remove_property_sysfs(ce->np, ce->prop);
  		break;
  	case OF_RECONFIG_UPDATE_PROPERTY:
  		__of_update_property_sysfs(ce->np, ce->prop, ce->old_prop);
  		break;
  	}
  
  	return 0;
  }
  
  static inline int __of_changeset_entry_revert(struct of_changeset_entry *ce)
  {
  	struct of_changeset_entry ce_inverted;
  
  	__of_changeset_entry_invert(ce, &ce_inverted);
  	return __of_changeset_entry_apply(&ce_inverted);
  }
  
  /**
   * of_changeset_init - Initialize a changeset for use
   *
   * @ocs:	changeset pointer
   *
   * Initialize a changeset structure
   */
  void of_changeset_init(struct of_changeset *ocs)
  {
  	memset(ocs, 0, sizeof(*ocs));
  	INIT_LIST_HEAD(&ocs->entries);
  }
  
  /**
   * of_changeset_destroy - Destroy a changeset
   *
   * @ocs:	changeset pointer
   *
   * Destroys a changeset. Note that if a changeset is applied,
   * its changes to the tree cannot be reverted.
   */
  void of_changeset_destroy(struct of_changeset *ocs)
  {
  	struct of_changeset_entry *ce, *cen;
  
  	list_for_each_entry_safe_reverse(ce, cen, &ocs->entries, node)
  		__of_changeset_entry_destroy(ce);
  }
  
  /**
   * of_changeset_apply - Applies a changeset
   *
   * @ocs:	changeset pointer
   *
   * Applies a changeset to the live tree.
   * Any side-effects of live tree state changes are applied here on
   * sucess, like creation/destruction of devices and side-effects
   * like creation of sysfs properties and directories.
   * Returns 0 on success, a negative error value in case of an error.
   * On error the partially applied effects are reverted.
   */
  int of_changeset_apply(struct of_changeset *ocs)
  {
  	struct of_changeset_entry *ce;
  	int ret;
  
  	/* perform the rest of the work */
  	pr_debug("of_changeset: applying...
  ");
  	list_for_each_entry(ce, &ocs->entries, node) {
  		ret = __of_changeset_entry_apply(ce);
  		if (ret) {
  			pr_err("%s: Error applying changeset (%d)
  ", __func__, ret);
  			list_for_each_entry_continue_reverse(ce, &ocs->entries, node)
  				__of_changeset_entry_revert(ce);
  			return ret;
  		}
  	}
  	pr_debug("of_changeset: applied, emitting notifiers.
  ");
  
  	/* drop the global lock while emitting notifiers */
  	mutex_unlock(&of_mutex);
  	list_for_each_entry(ce, &ocs->entries, node)
  		__of_changeset_entry_notify(ce, 0);
  	mutex_lock(&of_mutex);
  	pr_debug("of_changeset: notifiers sent.
  ");
  
  	return 0;
  }
  
  /**
   * of_changeset_revert - Reverts an applied changeset
   *
   * @ocs:	changeset pointer
   *
   * Reverts a changeset returning the state of the tree to what it
   * was before the application.
   * Any side-effects like creation/destruction of devices and
   * removal of sysfs properties and directories are applied.
   * Returns 0 on success, a negative error value in case of an error.
   */
  int of_changeset_revert(struct of_changeset *ocs)
  {
  	struct of_changeset_entry *ce;
  	int ret;
  
  	pr_debug("of_changeset: reverting...
  ");
  	list_for_each_entry_reverse(ce, &ocs->entries, node) {
  		ret = __of_changeset_entry_revert(ce);
  		if (ret) {
  			pr_err("%s: Error reverting changeset (%d)
  ", __func__, ret);
  			list_for_each_entry_continue(ce, &ocs->entries, node)
  				__of_changeset_entry_apply(ce);
  			return ret;
  		}
  	}
  	pr_debug("of_changeset: reverted, emitting notifiers.
  ");
  
  	/* drop the global lock while emitting notifiers */
  	mutex_unlock(&of_mutex);
  	list_for_each_entry_reverse(ce, &ocs->entries, node)
  		__of_changeset_entry_notify(ce, 1);
  	mutex_lock(&of_mutex);
  	pr_debug("of_changeset: notifiers sent.
  ");
  
  	return 0;
  }
  
  /**
   * of_changeset_action - Perform a changeset action
   *
   * @ocs:	changeset pointer
   * @action:	action to perform
   * @np:		Pointer to device node
   * @prop:	Pointer to property
   *
   * On action being one of:
   * + OF_RECONFIG_ATTACH_NODE
   * + OF_RECONFIG_DETACH_NODE,
   * + OF_RECONFIG_ADD_PROPERTY
   * + OF_RECONFIG_REMOVE_PROPERTY,
   * + OF_RECONFIG_UPDATE_PROPERTY
   * Returns 0 on success, a negative error value in case of an error.
   */
  int of_changeset_action(struct of_changeset *ocs, unsigned long action,
  		struct device_node *np, struct property *prop)
  {
  	struct of_changeset_entry *ce;
  
  	ce = kzalloc(sizeof(*ce), GFP_KERNEL);
  	if (!ce) {
  		pr_err("%s: Failed to allocate
  ", __func__);
  		return -ENOMEM;
  	}
  	/* get a reference to the node */
  	ce->action = action;
  	ce->np = of_node_get(np);
  	ce->prop = prop;
  
  	if (action == OF_RECONFIG_UPDATE_PROPERTY && prop)
  		ce->old_prop = of_find_property(np, prop->name, NULL);
  
  	/* add it to the list */
  	list_add_tail(&ce->node, &ocs->entries);
  	return 0;
  }