drivers/of/overlay.c - kernel/msm-5.4 - Gitiles

 /*
  * Functions for working with device tree overlays
  *
  * Copyright (C) 2012 Pantelis Antoniou <panto@antoniou-consulting.com>
  * Copyright (C) 2012 Texas Instruments Inc.
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License
  * version 2 as published by the Free Software Foundation.
  */

 #define pr_fmt(fmt)	"OF: overlay: " fmt

 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/of.h>
 #include <linux/of_device.h>
 #include <linux/string.h>
 #include <linux/ctype.h>
 #include <linux/errno.h>
 #include <linux/slab.h>
 #include <linux/err.h>
 #include <linux/idr.h>

 #include "of_private.h"

 /**
  * struct fragment - info about fragment nodes in overlay expanded device tree
  * @target:	target of the overlay operation
  * @overlay:	pointer to the __overlay__ node
  */
 struct fragment {
 	struct device_node *target;
 	struct device_node *overlay;
 	bool is_symbols_node;
 };

 /**
  * struct overlay_changeset
  * @ovcs_list:	list on which we are located
  * @count:	count of @fragments structures
  * @fragments:	info about fragment nodes in overlay expanded device tree
  * @cset:	changeset to apply fragments to live device tree
  */
 struct overlay_changeset {
 	int id;
 	struct list_head ovcs_list;
 	int count;
 	struct fragment *fragments;
 	struct of_changeset cset;
 };

 static int build_changeset_next_level(struct overlay_changeset *ovcs,
 		struct device_node *target_node,
 		const struct device_node *overlay_node,
 		bool is_symbols_node);

 static BLOCKING_NOTIFIER_HEAD(overlay_notify_chain);

 int of_overlay_notifier_register(struct notifier_block *nb)
 {
 	return blocking_notifier_chain_register(&overlay_notify_chain, nb);
 }
 EXPORT_SYMBOL_GPL(of_overlay_notifier_register);

 int of_overlay_notifier_unregister(struct notifier_block *nb)
 {
 	return blocking_notifier_chain_unregister(&overlay_notify_chain, nb);
 }
 EXPORT_SYMBOL_GPL(of_overlay_notifier_unregister);

 static int overlay_notify(struct overlay_changeset *ovcs,
 		enum of_overlay_notify_action action)
 {
 	struct of_overlay_notify_data nd;
 	int i, ret;

 	for (i = 0; i < ovcs->count; i++) {
 		struct fragment *fragment = &ovcs->fragments[i];

 		nd.target = fragment->target;
 		nd.overlay = fragment->overlay;

 		ret = blocking_notifier_call_chain(&overlay_notify_chain,
 						   action, &nd);
 		if (ret)
 			return notifier_to_errno(ret);
 	}

 	return 0;
 }

 static struct property *dup_and_fixup_symbol_prop(
 		struct overlay_changeset *ovcs, const struct property *prop)
 {
 	struct fragment *fragment;
 	struct property *new;
 	const char *overlay_name;
 	char *label_path;
 	char *symbol_path;
 	const char *target_path;
 	int k;
 	int label_path_len;
 	int overlay_name_len;
 	int target_path_len;

 	if (!prop->value)
 		return NULL;
 	symbol_path = prop->value;

 	new = kzalloc(sizeof(*new), GFP_KERNEL);
 	if (!new)
 		return NULL;

 	for (k = 0; k < ovcs->count; k++) {
 		fragment = &ovcs->fragments[k];
 		overlay_name = fragment->overlay->full_name;
 		overlay_name_len = strlen(overlay_name);
 		if (!strncasecmp(symbol_path, overlay_name, overlay_name_len))
 			break;
 	}

 	if (k >= ovcs->count)
 		goto err_free;

 	target_path = fragment->target->full_name;
 	target_path_len = strlen(target_path);

 	label_path = symbol_path + overlay_name_len;
 	label_path_len = strlen(label_path);

 	new->name = kstrdup(prop->name, GFP_KERNEL);
 	new->length = target_path_len + label_path_len + 1;
 	new->value = kzalloc(new->length, GFP_KERNEL);

 	if (!new->name || !new->value)
 		goto err_free;

 	strcpy(new->value, target_path);
 	strcpy(new->value + target_path_len, label_path);

 	of_property_set_flag(new, OF_DYNAMIC);

 	return new;

  err_free:
 	kfree(new->name);
 	kfree(new->value);
 	kfree(new);
 	return NULL;


 }

 /**
  * add_changeset_property() - add @overlay_prop to overlay changeset
  * @ovcs:		overlay changeset
  * @target_node:	where to place @overlay_prop in live tree
  * @overlay_prop:	property to add or update, from overlay tree
  * is_symbols_node:	1 if @target_node is "/__symbols__"
  *
  * If @overlay_prop does not already exist in @target_node, add changeset entry
  * to add @overlay_prop in @target_node, else add changeset entry to update
  * value of @overlay_prop.
  *
  * Some special properties are not updated (no error returned).
  *
  * Update of property in symbols node is not allowed.
  *
  * Returns 0 on success, -ENOMEM if memory allocation failure, or -EINVAL if
  * invalid @overlay.
  */
 static int add_changeset_property(struct overlay_changeset *ovcs,
 		struct device_node *target_node,
 		struct property *overlay_prop,
 		bool is_symbols_node)
 {
 	struct property *new_prop = NULL, *prop;
 	int ret = 0;

 	prop = of_find_property(target_node, overlay_prop->name, NULL);

 	if (!of_prop_cmp(overlay_prop->name, "name") ||
 	    !of_prop_cmp(overlay_prop->name, "phandle") ||
 	    !of_prop_cmp(overlay_prop->name, "linux,phandle"))
 		return 0;

 	if (is_symbols_node) {
 		if (prop)
 			return -EINVAL;
 		new_prop = dup_and_fixup_symbol_prop(ovcs, overlay_prop);
 	} else {
 		new_prop = __of_prop_dup(overlay_prop, GFP_KERNEL);
 	}

 	if (!new_prop)
 		return -ENOMEM;

 	if (!prop)
 		ret = of_changeset_add_property(&ovcs->cset, target_node,
 						new_prop);
 	else
 		ret = of_changeset_update_property(&ovcs->cset, target_node,
 						   new_prop);

 	if (ret) {
 		kfree(new_prop->name);
 		kfree(new_prop->value);
 		kfree(new_prop);
 	}
 	return ret;
 }

 /**
  * add_changeset_node() - add @node (and children) to overlay changeset
  * @ovcs:		overlay changeset
  * @target_node:	where to place @node in live tree
  * @node:		node from within overlay device tree fragment
  *
  * If @node does not already exist in @target_node, add changeset entry
  * to add @node in @target_node.
  *
  * If @node already exists in @target_node, and the existing node has
  * a phandle, the overlay node is not allowed to have a phandle.
  *
  * If @node has child nodes, add the children recursively via
  * build_changeset_next_level().
  *
  * NOTE: Multiple mods of created nodes not supported.
  *
  * Returns 0 on success, -ENOMEM if memory allocation failure, or -EINVAL if
  * invalid @overlay.
  */
 static int add_changeset_node(struct overlay_changeset *ovcs,
 		struct device_node *target_node, struct device_node *node)
 {
 	const char *node_kbasename;
 	struct device_node *tchild;
 	int ret = 0;

 	node_kbasename = kbasename(node->full_name);
 	if (!node_kbasename)
 		return -ENOMEM;

 	for_each_child_of_node(target_node, tchild)
 		if (!of_node_cmp(node_kbasename, kbasename(tchild->full_name)))
 			break;

 	if (tchild) {
 		if (node->phandle)
 			return -EINVAL;

 		ret = build_changeset_next_level(ovcs, tchild, node, 0);
 		of_node_put(tchild);
 	} else {
 		tchild = __of_node_dup(node, "%pOF/%s",
 				       target_node, node_kbasename);
 		if (!tchild)
 			return -ENOMEM;

 		tchild->parent = target_node;

 		ret = of_changeset_attach_node(&ovcs->cset, tchild);
 		if (ret)
 			return ret;

 		ret = build_changeset_next_level(ovcs, tchild, node, 0);
 		if (ret)
 			return ret;
 	}

 	return ret;
 }

 /**
  * build_changeset_next_level() - add level of overlay changeset
  * @ovcs:		overlay changeset
  * @target_node:	where to place @overlay_node in live tree
  * @overlay_node:	node from within an overlay device tree fragment
  * @is_symbols_node:	@overlay_node is node "/__symbols__"
  *
  * Add the properties (if any) and nodes (if any) from @overlay_node to the
  * @ovcs->cset changeset.  If an added node has child nodes, they will
  * be added recursively.
  *
  * Do not allow symbols node to have any children.
  *
  * Returns 0 on success, -ENOMEM if memory allocation failure, or -EINVAL if
  * invalid @overlay_node.
  */
 static int build_changeset_next_level(struct overlay_changeset *ovcs,
 		struct device_node *target_node,
 		const struct device_node *overlay_node,
 		bool is_symbols_node)
 {
 	struct device_node *child;
 	struct property *prop;
 	int ret;

 	for_each_property_of_node(overlay_node, prop) {
 		ret = add_changeset_property(ovcs, target_node, prop,
 					     is_symbols_node);
 		if (ret) {
 			pr_err("Failed to apply prop @%pOF/%s\n",
 			       target_node, prop->name);
 			return ret;
 		}
 	}

 	if (is_symbols_node)
 		return 0;

 	for_each_child_of_node(overlay_node, child) {
 		ret = add_changeset_node(ovcs, target_node, child);
 		if (ret) {
 			pr_err("Failed to apply node @%pOF/%s\n",
 			       target_node, child->name);
 			of_node_put(child);
 			return ret;
 		}
 	}

 	return 0;
 }

 /**
  * build_changeset() - populate overlay changeset in @ovcs from @ovcs->fragments
  * @ovcs:	Overlay changeset
  *
  * Create changeset @ovcs->cset to contain the nodes and properties of the
  * overlay device tree fragments in @ovcs->fragments[].  If an error occurs,
  * any portions of the changeset that were successfully created will remain
  * in @ovcs->cset.
  *
  * Returns 0 on success, -ENOMEM if memory allocation failure, or -EINVAL if
  * invalid overlay in @ovcs->fragments[].
  */
 static int build_changeset(struct overlay_changeset *ovcs)
 {
 	int i, ret;

 	for (i = 0; i < ovcs->count; i++) {
 		struct fragment *fragment = &ovcs->fragments[i];

 		ret = build_changeset_next_level(ovcs, fragment->target,
 					       fragment->overlay,
 					       fragment->is_symbols_node);
 		if (ret) {
 			pr_err("apply failed '%pOF'\n", fragment->target);
 			return ret;
 		}
 	}

 	return 0;
 }

 /*
  * Find the target node using a number of different strategies
  * in order of preference:
  *
  * 1) "target" property containing the phandle of the target
  * 2) "target-path" property containing the path of the target
  */
 static struct device_node *find_target_node(struct device_node *info_node)
 {
 	const char *path;
 	u32 val;
 	int ret;

 	ret = of_property_read_u32(info_node, "target", &val);
 	if (!ret)
 		return of_find_node_by_phandle(val);

 	ret = of_property_read_string(info_node, "target-path", &path);
 	if (!ret)
 		return of_find_node_by_path(path);

 	pr_err("Failed to find target for node %p (%s)\n",
 		info_node, info_node->name);

 	return NULL;
 }

 /**
  * of_fill_overlay_info() - Fill an overlay info structure
  * @ov		Overlay to fill
  * @info_node:	Device node containing the overlay
  * @ovinfo:	Pointer to the overlay info structure to fill
  *
  * Fills an overlay info structure with the overlay information
  * from a device node. This device node must have a target property
  * which contains a phandle of the overlay target node, and an
  * __overlay__ child node which has the overlay contents.
  * Both ovinfo->target & ovinfo->overlay have their references taken.
  *
  * Returns 0 on success, or a negative error value.
  */
 static int of_fill_overlay_info(struct overlay_changeset *ovcset,
 		struct device_node *info_node, struct fragment *fragment)
 {
 	fragment->overlay = of_get_child_by_name(info_node, "__overlay__");
 	if (!fragment->overlay)
 		goto err_fail;

 	fragment->target = find_target_node(info_node);
 	if (!fragment->target)
 		goto err_fail;

 	return 0;

 err_fail:
 	of_node_put(fragment->target);
 	of_node_put(fragment->overlay);

 	memset(fragment, 0, sizeof(*fragment));
 	return -EINVAL;
 }

 /**
  * init_overlay_changeset() - initialize overlay changeset from overlay tree
  * @ovcs	Overlay changeset to build
  * @tree:	Contains all the overlay fragments and overlay fixup nodes
  *
  * Initialize @ovcs.  Populate @ovcs->fragments with node information from
  * the top level of @tree.  The relevant top level nodes are the fragment
  * nodes and the __symbols__ node.  Any other top level node will be ignored.
  *
  * Returns 0 on success, -ENOMEM if memory allocation failure, -EINVAL if error
  * detected in @tree, or -ENODEV if no valid nodes found.
  */
 static int init_overlay_changeset(struct overlay_changeset *ovcs,
 		struct device_node *tree)
 {
 	struct device_node *node;
 	struct fragment *fragment;
 	struct fragment *fragments;
 	int cnt, ret;

 	cnt = 0;
 	for_each_child_of_node(tree, node)
 		cnt++;

 	if (of_get_child_by_name(tree, "__symbols__"))
 		cnt++;

 	fragments = kcalloc(cnt, sizeof(*fragments), GFP_KERNEL);
 	if (!fragments)
 		return -ENOMEM;

 	cnt = 0;
 	for_each_child_of_node(tree, node) {
 		ret = of_fill_overlay_info(ovcs, node, &fragments[cnt]);
 		if (!ret)
 			cnt++;
 	}

 	node = of_get_child_by_name(tree, "__symbols__");
 	if (node) {
 		fragment = &fragments[cnt];
 		fragment->overlay = node;
 		fragment->target = of_find_node_by_path("/__symbols__");
 		fragment->is_symbols_node = 1;

 		if (!fragment->target) {
 			pr_err("no symbols in root of device tree.\n");
 			return -EINVAL;
 		}

 		cnt++;
 	}

 	if (!cnt) {
 		kfree(fragments);
 		return -ENODEV;
 	}

 	ovcs->count = cnt;
 	ovcs->fragments = fragments;

 	return 0;
 }

 /**
  * free_overlay_fragments() - Free a fragments array
  * @ovcs	Overlay to free the overlay info from
  *
  * Frees the memory of an ovcs->fragments[] array.
  */
 static void free_overlay_fragments(struct overlay_changeset *ovcs)
 {
 	int i;

 	/* do it in reverse */
 	for (i = ovcs->count - 1; i >= 0; i--) {
 		of_node_put(ovcs->fragments[i].target);
 		of_node_put(ovcs->fragments[i].overlay);
 	}

 	kfree(ovcs->fragments);
 }

 static LIST_HEAD(ovcs_list);
 static DEFINE_IDR(ovcs_idr);

 /**
  * of_overlay_apply() - Create and apply an overlay changeset
  * @tree:	Expanded overlay device tree
  *
  * Creates and applies an overlay changeset.  If successful, the overlay
  * changeset is added to the overlay changeset list.
  *
  * Returns the id of the created overlay changeset, or a negative error number
  */
 int of_overlay_apply(struct device_node *tree)
 {
 	struct overlay_changeset *ovcs;
 	int id, ret;

 	ovcs = kzalloc(sizeof(*ovcs), GFP_KERNEL);
 	if (!ovcs)
 		return -ENOMEM;
 	ovcs->id = -1;

 	INIT_LIST_HEAD(&ovcs->ovcs_list);

 	of_changeset_init(&ovcs->cset);

 	mutex_lock(&of_mutex);

 	id = idr_alloc(&ovcs_idr, ovcs, 0, 0, GFP_KERNEL);
 	if (id < 0) {
 		ret = id;
 		goto err_destroy_trans;
 	}
 	ovcs->id = id;

 	ret = init_overlay_changeset(ovcs, tree);
 	if (ret) {
 		pr_err("init_overlay_changeset() failed for tree@%pOF\n",
 		       tree);
 		goto err_free_idr;
 	}

 	ret = overlay_notify(ovcs, OF_OVERLAY_PRE_APPLY);
 	if (ret < 0) {
 		pr_err("%s: Pre-apply notifier failed (ret=%d)\n",
 		       __func__, ret);
 		goto err_free_overlay_fragments;
 	}

 	ret = build_changeset(ovcs);
 	if (ret)
 		goto err_free_overlay_fragments;

 	ret = __of_changeset_apply(&ovcs->cset);
 	if (ret)
 		goto err_free_overlay_fragments;

 	list_add_tail(&ovcs->ovcs_list, &ovcs_list);

 	overlay_notify(ovcs, OF_OVERLAY_POST_APPLY);

 	mutex_unlock(&of_mutex);

 	return id;

 err_free_overlay_fragments:
 	free_overlay_fragments(ovcs);
 err_free_idr:
 	idr_remove(&ovcs_idr, ovcs->id);
 err_destroy_trans:
 	of_changeset_destroy(&ovcs->cset);
 	kfree(ovcs);
 	mutex_unlock(&of_mutex);

 	return ret;
 }
 EXPORT_SYMBOL_GPL(of_overlay_apply);

 /*
  * Find @np in @tree.
  *
  * Returns 1 if @np is @tree or is contained in @tree, else 0
  */
 static int find_node(struct device_node *tree, struct device_node *np)
 {
 	struct device_node *child;

 	if (tree == np)
 		return 1;

 	for_each_child_of_node(tree, child) {
 		if (find_node(child, np)) {
 			of_node_put(child);
 			return 1;
 		}
 	}

 	return 0;
 }

 /*
  * Is @remove_ce_np a child of or the same as any
  * node in an overlay changeset more topmost than @remove_ovcs?
  *
  * Returns 1 if found, else 0
  */
 static int node_in_later_cs(struct overlay_changeset *remove_ovcs,
 		struct device_node *remove_ce_np)
 {
 	struct overlay_changeset *ovcs;
 	struct of_changeset_entry *ce;

 	list_for_each_entry_reverse(ovcs, &ovcs_list, ovcs_list) {
 		if (ovcs == remove_ovcs)
 			break;

 		list_for_each_entry(ce, &ovcs->cset.entries, node) {
 			if (find_node(ce->np, remove_ce_np)) {
 				pr_err("%s: #%d clashes #%d @%pOF\n",
 					__func__, remove_ovcs->id, ovcs->id,
 					remove_ce_np);
 				return 1;
 			}
 		}
 	}

 	return 0;
 }

 /*
  * We can safely remove the overlay only if it's the top-most one.
  * Newly applied overlays are inserted at the tail of the overlay list,
  * so a top most overlay is the one that is closest to the tail.
  *
  * The topmost check is done by exploiting this property. For each
  * affected device node in the log list we check if this overlay is
  * the one closest to the tail. If another overlay has affected this
  * device node and is closest to the tail, then removal is not permited.
  */
 static int overlay_removal_is_ok(struct overlay_changeset *remove_ovcs)
 {
 	struct of_changeset_entry *remove_ce;

 	list_for_each_entry(remove_ce, &remove_ovcs->cset.entries, node) {
 		if (node_in_later_cs(remove_ovcs, remove_ce->np)) {
 			pr_err("overlay #%d is not topmost\n", remove_ovcs->id);
 			return 0;
 		}
 	}

 	return 1;
 }

 /**
  * of_overlay_remove() - Revert and free an overlay changeset
  * @ovcs_id:	Overlay changeset id number
  *
  * Removes an overlay if it is permissible.  ovcs_id was previously returned
  * by of_overlay_apply().
  *
  * Returns 0 on success, or a negative error number
  */
 int of_overlay_remove(int ovcs_id)
 {
 	struct overlay_changeset *ovcs;
 	int ret = 0;

 	mutex_lock(&of_mutex);

 	ovcs = idr_find(&ovcs_idr, ovcs_id);
 	if (!ovcs) {
 		ret = -ENODEV;
 		pr_err("remove: Could not find overlay #%d\n", ovcs_id);
 		goto out;
 	}

 	if (!overlay_removal_is_ok(ovcs)) {
 		ret = -EBUSY;
 		goto out;
 	}

 	overlay_notify(ovcs, OF_OVERLAY_PRE_REMOVE);
 	list_del(&ovcs->ovcs_list);
 	__of_changeset_revert(&ovcs->cset);
 	overlay_notify(ovcs, OF_OVERLAY_POST_REMOVE);
 	free_overlay_fragments(ovcs);
 	idr_remove(&ovcs_idr, ovcs_id);
 	of_changeset_destroy(&ovcs->cset);
 	kfree(ovcs);

 out:
 	mutex_unlock(&of_mutex);

 	return ret;
 }
 EXPORT_SYMBOL_GPL(of_overlay_remove);

 /**
  * of_overlay_remove_all() - Reverts and frees all overlay changesets
  *
  * Removes all overlays from the system in the correct order.
  *
  * Returns 0 on success, or a negative error number
  */
 int of_overlay_remove_all(void)
 {
 	struct overlay_changeset *ovcs, *ovcs_n;

 	mutex_lock(&of_mutex);

 	/* the tail of list is guaranteed to be safe to remove */
 	list_for_each_entry_safe_reverse(ovcs, ovcs_n, &ovcs_list, ovcs_list) {
 		list_del(&ovcs->ovcs_list);
 		__of_changeset_revert(&ovcs->cset);
 		free_overlay_fragments(ovcs);
 		idr_remove(&ovcs_idr, ovcs->id);
 		kfree(ovcs);
 	}

 	mutex_unlock(&of_mutex);

 	return 0;
 }
 EXPORT_SYMBOL_GPL(of_overlay_remove_all);
	/*
	* Functions for working with device tree overlays
	*
	* Copyright (C) 2012 Pantelis Antoniou <panto@antoniou-consulting.com>
	* Copyright (C) 2012 Texas Instruments Inc.
	*
	* This program is free software; you can redistribute it and/or
	* modify it under the terms of the GNU General Public License
	* version 2 as published by the Free Software Foundation.
	*/

	#define pr_fmt(fmt) "OF: overlay: " fmt

	#include <linux/kernel.h>
	#include <linux/module.h>
	#include <linux/of.h>
	#include <linux/of_device.h>
	#include <linux/string.h>
	#include <linux/ctype.h>
	#include <linux/errno.h>
	#include <linux/slab.h>
	#include <linux/err.h>
	#include <linux/idr.h>

	#include "of_private.h"

	/**
	* struct fragment - info about fragment nodes in overlay expanded device tree
	* @target: target of the overlay operation
	* @overlay: pointer to the __overlay__ node
	*/
	struct fragment {
	struct device_node *target;
	struct device_node *overlay;
	bool is_symbols_node;
	};

	/**
	* struct overlay_changeset
	* @ovcs_list: list on which we are located
	* @count: count of @fragments structures
	* @fragments: info about fragment nodes in overlay expanded device tree
	* @cset: changeset to apply fragments to live device tree
	*/
	struct overlay_changeset {
	int id;
	struct list_head ovcs_list;
	int count;
	struct fragment *fragments;
	struct of_changeset cset;
	};

	static int build_changeset_next_level(struct overlay_changeset *ovcs,
	struct device_node *target_node,
	const struct device_node *overlay_node,
	bool is_symbols_node);

	static BLOCKING_NOTIFIER_HEAD(overlay_notify_chain);

	int of_overlay_notifier_register(struct notifier_block *nb)
	{
	return blocking_notifier_chain_register(&overlay_notify_chain, nb);
	}
	EXPORT_SYMBOL_GPL(of_overlay_notifier_register);

	int of_overlay_notifier_unregister(struct notifier_block *nb)
	{
	return blocking_notifier_chain_unregister(&overlay_notify_chain, nb);
	}
	EXPORT_SYMBOL_GPL(of_overlay_notifier_unregister);

	static int overlay_notify(struct overlay_changeset *ovcs,
	enum of_overlay_notify_action action)
	{
	struct of_overlay_notify_data nd;
	int i, ret;

	for (i = 0; i < ovcs->count; i++) {
	struct fragment *fragment = &ovcs->fragments[i];

	nd.target = fragment->target;
	nd.overlay = fragment->overlay;

	ret = blocking_notifier_call_chain(&overlay_notify_chain,
	action, &nd);
	if (ret)
	return notifier_to_errno(ret);
	}

	return 0;
	}

	static struct property *dup_and_fixup_symbol_prop(
	struct overlay_changeset ovcs, const struct property prop)
	{
	struct fragment *fragment;
	struct property *new;
	const char *overlay_name;
	char *label_path;
	char *symbol_path;
	const char *target_path;
	int k;
	int label_path_len;
	int overlay_name_len;
	int target_path_len;

	if (!prop->value)
	return NULL;
	symbol_path = prop->value;

	new = kzalloc(sizeof(*new), GFP_KERNEL);
	if (!new)
	return NULL;

	for (k = 0; k < ovcs->count; k++) {
	fragment = &ovcs->fragments[k];
	overlay_name = fragment->overlay->full_name;
	overlay_name_len = strlen(overlay_name);
	if (!strncasecmp(symbol_path, overlay_name, overlay_name_len))
	break;
	}

	if (k >= ovcs->count)
	goto err_free;

	target_path = fragment->target->full_name;
	target_path_len = strlen(target_path);

	label_path = symbol_path + overlay_name_len;
	label_path_len = strlen(label_path);

	new->name = kstrdup(prop->name, GFP_KERNEL);
	new->length = target_path_len + label_path_len + 1;
	new->value = kzalloc(new->length, GFP_KERNEL);

	if (!new->name \|\| !new->value)
	goto err_free;

	strcpy(new->value, target_path);
	strcpy(new->value + target_path_len, label_path);

	of_property_set_flag(new, OF_DYNAMIC);

	return new;

	err_free:
	kfree(new->name);
	kfree(new->value);
	kfree(new);
	return NULL;


	}

	/**
	* add_changeset_property() - add @overlay_prop to overlay changeset
	* @ovcs: overlay changeset
	* @target_node: where to place @overlay_prop in live tree
	* @overlay_prop: property to add or update, from overlay tree
	* is_symbols_node: 1 if @target_node is "/__symbols__"
	*
	* If @overlay_prop does not already exist in @target_node, add changeset entry
	* to add @overlay_prop in @target_node, else add changeset entry to update
	* value of @overlay_prop.
	*
	* Some special properties are not updated (no error returned).
	*
	* Update of property in symbols node is not allowed.
	*
	* Returns 0 on success, -ENOMEM if memory allocation failure, or -EINVAL if
	* invalid @overlay.
	*/
	static int add_changeset_property(struct overlay_changeset *ovcs,
	struct device_node *target_node,
	struct property *overlay_prop,
	bool is_symbols_node)
	{
	struct property new_prop = NULL, prop;
	int ret = 0;

	prop = of_find_property(target_node, overlay_prop->name, NULL);

	if (!of_prop_cmp(overlay_prop->name, "name") \|\|
	!of_prop_cmp(overlay_prop->name, "phandle") \|\|
	!of_prop_cmp(overlay_prop->name, "linux,phandle"))
	return 0;

	if (is_symbols_node) {
	if (prop)
	return -EINVAL;
	new_prop = dup_and_fixup_symbol_prop(ovcs, overlay_prop);
	} else {
	new_prop = __of_prop_dup(overlay_prop, GFP_KERNEL);
	}

	if (!new_prop)
	return -ENOMEM;

	if (!prop)
	ret = of_changeset_add_property(&ovcs->cset, target_node,
	new_prop);
	else
	ret = of_changeset_update_property(&ovcs->cset, target_node,
	new_prop);

	if (ret) {
	kfree(new_prop->name);
	kfree(new_prop->value);
	kfree(new_prop);
	}
	return ret;
	}

	/**
	* add_changeset_node() - add @node (and children) to overlay changeset
	* @ovcs: overlay changeset
	* @target_node: where to place @node in live tree
	* @node: node from within overlay device tree fragment
	*
	* If @node does not already exist in @target_node, add changeset entry
	* to add @node in @target_node.
	*
	* If @node already exists in @target_node, and the existing node has
	* a phandle, the overlay node is not allowed to have a phandle.
	*
	* If @node has child nodes, add the children recursively via
	* build_changeset_next_level().
	*
	* NOTE: Multiple mods of created nodes not supported.
	*
	* Returns 0 on success, -ENOMEM if memory allocation failure, or -EINVAL if
	* invalid @overlay.
	*/
	static int add_changeset_node(struct overlay_changeset *ovcs,
	struct device_node target_node, struct device_node node)
	{
	const char *node_kbasename;
	struct device_node *tchild;
	int ret = 0;

	node_kbasename = kbasename(node->full_name);
	if (!node_kbasename)
	return -ENOMEM;

	for_each_child_of_node(target_node, tchild)
	if (!of_node_cmp(node_kbasename, kbasename(tchild->full_name)))
	break;

	if (tchild) {
	if (node->phandle)
	return -EINVAL;

	ret = build_changeset_next_level(ovcs, tchild, node, 0);
	of_node_put(tchild);
	} else {
	tchild = __of_node_dup(node, "%pOF/%s",
	target_node, node_kbasename);
	if (!tchild)
	return -ENOMEM;

	tchild->parent = target_node;

	ret = of_changeset_attach_node(&ovcs->cset, tchild);
	if (ret)
	return ret;

	ret = build_changeset_next_level(ovcs, tchild, node, 0);
	if (ret)
	return ret;
	}

	return ret;
	}

	/**
	* build_changeset_next_level() - add level of overlay changeset
	* @ovcs: overlay changeset
	* @target_node: where to place @overlay_node in live tree
	* @overlay_node: node from within an overlay device tree fragment
	* @is_symbols_node: @overlay_node is node "/__symbols__"
	*
	* Add the properties (if any) and nodes (if any) from @overlay_node to the
	* @ovcs->cset changeset. If an added node has child nodes, they will
	* be added recursively.
	*
	* Do not allow symbols node to have any children.
	*
	* Returns 0 on success, -ENOMEM if memory allocation failure, or -EINVAL if
	* invalid @overlay_node.
	*/
	static int build_changeset_next_level(struct overlay_changeset *ovcs,
	struct device_node *target_node,
	const struct device_node *overlay_node,
	bool is_symbols_node)
	{
	struct device_node *child;
	struct property *prop;
	int ret;

	for_each_property_of_node(overlay_node, prop) {
	ret = add_changeset_property(ovcs, target_node, prop,
	is_symbols_node);
	if (ret) {
	pr_err("Failed to apply prop @%pOF/%s\n",
	target_node, prop->name);
	return ret;
	}
	}

	if (is_symbols_node)
	return 0;

	for_each_child_of_node(overlay_node, child) {
	ret = add_changeset_node(ovcs, target_node, child);
	if (ret) {
	pr_err("Failed to apply node @%pOF/%s\n",
	target_node, child->name);
	of_node_put(child);
	return ret;
	}
	}

	return 0;
	}

	/**
	* build_changeset() - populate overlay changeset in @ovcs from @ovcs->fragments
	* @ovcs: Overlay changeset
	*
	* Create changeset @ovcs->cset to contain the nodes and properties of the
	* overlay device tree fragments in @ovcs->fragments[]. If an error occurs,
	* any portions of the changeset that were successfully created will remain
	* in @ovcs->cset.
	*
	* Returns 0 on success, -ENOMEM if memory allocation failure, or -EINVAL if
	* invalid overlay in @ovcs->fragments[].
	*/
	static int build_changeset(struct overlay_changeset *ovcs)
	{
	int i, ret;

	for (i = 0; i < ovcs->count; i++) {
	struct fragment *fragment = &ovcs->fragments[i];

	ret = build_changeset_next_level(ovcs, fragment->target,
	fragment->overlay,
	fragment->is_symbols_node);
	if (ret) {
	pr_err("apply failed '%pOF'\n", fragment->target);
	return ret;
	}
	}

	return 0;
	}

	/*
	* Find the target node using a number of different strategies
	* in order of preference:
	*
	* 1) "target" property containing the phandle of the target
	* 2) "target-path" property containing the path of the target
	*/
	static struct device_node find_target_node(struct device_node info_node)
	{
	const char *path;
	u32 val;
	int ret;

	ret = of_property_read_u32(info_node, "target", &val);
	if (!ret)
	return of_find_node_by_phandle(val);

	ret = of_property_read_string(info_node, "target-path", &path);
	if (!ret)
	return of_find_node_by_path(path);

	pr_err("Failed to find target for node %p (%s)\n",
	info_node, info_node->name);

	return NULL;
	}

	/**
	* of_fill_overlay_info() - Fill an overlay info structure
	* @ov Overlay to fill
	* @info_node: Device node containing the overlay
	* @ovinfo: Pointer to the overlay info structure to fill
	*
	* Fills an overlay info structure with the overlay information
	* from a device node. This device node must have a target property
	* which contains a phandle of the overlay target node, and an
	* __overlay__ child node which has the overlay contents.
	* Both ovinfo->target & ovinfo->overlay have their references taken.
	*
	* Returns 0 on success, or a negative error value.
	*/
	static int of_fill_overlay_info(struct overlay_changeset *ovcset,
	struct device_node info_node, struct fragment fragment)
	{
	fragment->overlay = of_get_child_by_name(info_node, "__overlay__");
	if (!fragment->overlay)
	goto err_fail;

	fragment->target = find_target_node(info_node);
	if (!fragment->target)
	goto err_fail;

	return 0;

	err_fail:
	of_node_put(fragment->target);
	of_node_put(fragment->overlay);

	memset(fragment, 0, sizeof(*fragment));
	return -EINVAL;
	}

	/**
	* init_overlay_changeset() - initialize overlay changeset from overlay tree
	* @ovcs Overlay changeset to build
	* @tree: Contains all the overlay fragments and overlay fixup nodes
	*
	* Initialize @ovcs. Populate @ovcs->fragments with node information from
	* the top level of @tree. The relevant top level nodes are the fragment
	* nodes and the __symbols__ node. Any other top level node will be ignored.
	*
	* Returns 0 on success, -ENOMEM if memory allocation failure, -EINVAL if error
	* detected in @tree, or -ENODEV if no valid nodes found.
	*/
	static int init_overlay_changeset(struct overlay_changeset *ovcs,
	struct device_node *tree)
	{
	struct device_node *node;
	struct fragment *fragment;
	struct fragment *fragments;
	int cnt, ret;

	cnt = 0;
	for_each_child_of_node(tree, node)
	cnt++;

	if (of_get_child_by_name(tree, "__symbols__"))
	cnt++;

	fragments = kcalloc(cnt, sizeof(*fragments), GFP_KERNEL);
	if (!fragments)
	return -ENOMEM;

	cnt = 0;
	for_each_child_of_node(tree, node) {
	ret = of_fill_overlay_info(ovcs, node, &fragments[cnt]);
	if (!ret)
	cnt++;
	}

	node = of_get_child_by_name(tree, "__symbols__");
	if (node) {
	fragment = &fragments[cnt];
	fragment->overlay = node;
	fragment->target = of_find_node_by_path("/__symbols__");
	fragment->is_symbols_node = 1;

	if (!fragment->target) {
	pr_err("no symbols in root of device tree.\n");
	return -EINVAL;
	}

	cnt++;
	}

	if (!cnt) {
	kfree(fragments);
	return -ENODEV;
	}

	ovcs->count = cnt;
	ovcs->fragments = fragments;

	return 0;
	}

	/**
	* free_overlay_fragments() - Free a fragments array
	* @ovcs Overlay to free the overlay info from
	*
	* Frees the memory of an ovcs->fragments[] array.
	*/
	static void free_overlay_fragments(struct overlay_changeset *ovcs)
	{
	int i;

	/* do it in reverse */
	for (i = ovcs->count - 1; i >= 0; i--) {
	of_node_put(ovcs->fragments[i].target);
	of_node_put(ovcs->fragments[i].overlay);
	}

	kfree(ovcs->fragments);
	}

	static LIST_HEAD(ovcs_list);
	static DEFINE_IDR(ovcs_idr);

	/**
	* of_overlay_apply() - Create and apply an overlay changeset
	* @tree: Expanded overlay device tree
	*
	* Creates and applies an overlay changeset. If successful, the overlay
	* changeset is added to the overlay changeset list.
	*
	* Returns the id of the created overlay changeset, or a negative error number
	*/
	int of_overlay_apply(struct device_node *tree)
	{
	struct overlay_changeset *ovcs;
	int id, ret;

	ovcs = kzalloc(sizeof(*ovcs), GFP_KERNEL);
	if (!ovcs)
	return -ENOMEM;
	ovcs->id = -1;

	INIT_LIST_HEAD(&ovcs->ovcs_list);

	of_changeset_init(&ovcs->cset);

	mutex_lock(&of_mutex);

	id = idr_alloc(&ovcs_idr, ovcs, 0, 0, GFP_KERNEL);
	if (id < 0) {
	ret = id;
	goto err_destroy_trans;
	}
	ovcs->id = id;

	ret = init_overlay_changeset(ovcs, tree);
	if (ret) {
	pr_err("init_overlay_changeset() failed for tree@%pOF\n",
	tree);
	goto err_free_idr;
	}

	ret = overlay_notify(ovcs, OF_OVERLAY_PRE_APPLY);
	if (ret < 0) {
	pr_err("%s: Pre-apply notifier failed (ret=%d)\n",
	__func__, ret);
	goto err_free_overlay_fragments;
	}

	ret = build_changeset(ovcs);
	if (ret)
	goto err_free_overlay_fragments;

	ret = __of_changeset_apply(&ovcs->cset);
	if (ret)
	goto err_free_overlay_fragments;

	list_add_tail(&ovcs->ovcs_list, &ovcs_list);

	overlay_notify(ovcs, OF_OVERLAY_POST_APPLY);

	mutex_unlock(&of_mutex);

	return id;

	err_free_overlay_fragments:
	free_overlay_fragments(ovcs);
	err_free_idr:
	idr_remove(&ovcs_idr, ovcs->id);
	err_destroy_trans:
	of_changeset_destroy(&ovcs->cset);
	kfree(ovcs);
	mutex_unlock(&of_mutex);

	return ret;
	}
	EXPORT_SYMBOL_GPL(of_overlay_apply);

	/*
	* Find @np in @tree.
	*
	* Returns 1 if @np is @tree or is contained in @tree, else 0
	*/
	static int find_node(struct device_node tree, struct device_node np)
	{
	struct device_node *child;

	if (tree == np)
	return 1;

	for_each_child_of_node(tree, child) {
	if (find_node(child, np)) {
	of_node_put(child);
	return 1;
	}
	}

	return 0;
	}

	/*
	* Is @remove_ce_np a child of or the same as any
	* node in an overlay changeset more topmost than @remove_ovcs?
	*
	* Returns 1 if found, else 0
	*/
	static int node_in_later_cs(struct overlay_changeset *remove_ovcs,
	struct device_node *remove_ce_np)
	{
	struct overlay_changeset *ovcs;
	struct of_changeset_entry *ce;

	list_for_each_entry_reverse(ovcs, &ovcs_list, ovcs_list) {
	if (ovcs == remove_ovcs)
	break;

	list_for_each_entry(ce, &ovcs->cset.entries, node) {
	if (find_node(ce->np, remove_ce_np)) {
	pr_err("%s: #%d clashes #%d @%pOF\n",
	__func__, remove_ovcs->id, ovcs->id,
	remove_ce_np);
	return 1;
	}
	}
	}

	return 0;
	}

	/*
	* We can safely remove the overlay only if it's the top-most one.
	* Newly applied overlays are inserted at the tail of the overlay list,
	* so a top most overlay is the one that is closest to the tail.
	*
	* The topmost check is done by exploiting this property. For each
	* affected device node in the log list we check if this overlay is
	* the one closest to the tail. If another overlay has affected this
	* device node and is closest to the tail, then removal is not permited.
	*/
	static int overlay_removal_is_ok(struct overlay_changeset *remove_ovcs)
	{
	struct of_changeset_entry *remove_ce;

	list_for_each_entry(remove_ce, &remove_ovcs->cset.entries, node) {
	if (node_in_later_cs(remove_ovcs, remove_ce->np)) {
	pr_err("overlay #%d is not topmost\n", remove_ovcs->id);
	return 0;
	}
	}

	return 1;
	}

	/**
	* of_overlay_remove() - Revert and free an overlay changeset
	* @ovcs_id: Overlay changeset id number
	*
	* Removes an overlay if it is permissible. ovcs_id was previously returned
	* by of_overlay_apply().
	*
	* Returns 0 on success, or a negative error number
	*/
	int of_overlay_remove(int ovcs_id)
	{
	struct overlay_changeset *ovcs;
	int ret = 0;

	mutex_lock(&of_mutex);

	ovcs = idr_find(&ovcs_idr, ovcs_id);
	if (!ovcs) {
	ret = -ENODEV;
	pr_err("remove: Could not find overlay #%d\n", ovcs_id);
	goto out;
	}

	if (!overlay_removal_is_ok(ovcs)) {
	ret = -EBUSY;
	goto out;
	}

	overlay_notify(ovcs, OF_OVERLAY_PRE_REMOVE);
	list_del(&ovcs->ovcs_list);
	__of_changeset_revert(&ovcs->cset);
	overlay_notify(ovcs, OF_OVERLAY_POST_REMOVE);
	free_overlay_fragments(ovcs);
	idr_remove(&ovcs_idr, ovcs_id);
	of_changeset_destroy(&ovcs->cset);
	kfree(ovcs);

	out:
	mutex_unlock(&of_mutex);

	return ret;
	}
	EXPORT_SYMBOL_GPL(of_overlay_remove);

	/**
	* of_overlay_remove_all() - Reverts and frees all overlay changesets
	*
	* Removes all overlays from the system in the correct order.
	*
	* Returns 0 on success, or a negative error number
	*/
	int of_overlay_remove_all(void)
	{
	struct overlay_changeset ovcs, ovcs_n;

	mutex_lock(&of_mutex);

	/* the tail of list is guaranteed to be safe to remove */
	list_for_each_entry_safe_reverse(ovcs, ovcs_n, &ovcs_list, ovcs_list) {
	list_del(&ovcs->ovcs_list);
	__of_changeset_revert(&ovcs->cset);
	free_overlay_fragments(ovcs);
	idr_remove(&ovcs_idr, ovcs->id);
	kfree(ovcs);
	}

	mutex_unlock(&of_mutex);

	return 0;
	}
	EXPORT_SYMBOL_GPL(of_overlay_remove_all);