Linux 5.9.7

[linux/fpc-iii.git] / drivers / of / dynamic.c

// SPDX-License-Identifier: GPL-2.0
/*
 * 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.
 */

#define pr_fmt(fmt)     "OF: " fmt

#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"

static struct device_node *kobj_to_device_node(struct kobject *kobj)
{
        return container_of(kobj, struct device_node, kobj);
}

/**
 * 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);

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("notify %-15s %pOF\n", action_names[action],
                        pr->dn);
                break;
        case OF_RECONFIG_ADD_PROPERTY:
        case OF_RECONFIG_REMOVE_PROPERTY:
        case OF_RECONFIG_UPDATE_PROPERTY:
                pr_debug("notify %-15s %pOF:%s\n", action_names[action],
                        pr->dn, 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);
}

static void __of_attach_node(struct device_node *np)
{
        const __be32 *phandle;
        int sz;

        if (!of_node_check_flag(np, OF_OVERLAY)) {
                np->name = __of_get_property(np, "name", NULL);
                if (!np->name)
                        np->name = "<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);
                if (phandle && (sz >= 4))
                        np->phandle = be32_to_cpup(phandle);
                else
                        np->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);

        /* race with of_find_node_by_phandle() prevented by devtree_lock */
        __of_phandle_cache_inv_entry(np->phandle);
}

/**
 * of_detach_node() - "Unplug" a node from the device tree.
 */
int of_detach_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_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 0;
}
EXPORT_SYMBOL_GPL(of_detach_node);

static void property_list_free(struct property *prop_list)
{
        struct property *prop, *next;

        for (prop = prop_list; prop != NULL; prop = next) {
                next = prop->next;
                kfree(prop->name);
                kfree(prop->value);
                kfree(prop);
        }
}

/**
 * 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);

        /* 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 %pOF\n", node);
                dump_stack();
                return;
        }
        if (!of_node_check_flag(node, OF_DYNAMIC))
                return;

        if (of_node_check_flag(node, OF_OVERLAY)) {

                if (!of_node_check_flag(node, OF_OVERLAY_FREE_CSET)) {
                        /* premature refcount of zero, do not free memory */
                        pr_err("ERROR: memory leak before free overlay changeset,  %pOF\n",
                               node);
                        return;
                }

                /*
                 * If node->properties non-empty then properties were added
                 * to this node either by different overlay that has not
                 * yet been removed, or by a non-overlay mechanism.
                 */
                if (node->properties)
                        pr_err("ERROR: %s(), unexpected properties in %pOF\n",
                               __func__, node);
        }

        property_list_free(node->properties);
        property_list_free(node->deadprops);

        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.
 * @np:         if not NULL, contains properties to be duplicated in new node
 * @full_name:  string value to be duplicated into new node's full_name field
 *
 * Create a device tree node, optionally duplicating the properties of
 * another node.  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 *full_name)
{
        struct device_node *node;

        node = kzalloc(sizeof(*node), GFP_KERNEL);
        if (!node)
                return NULL;
        node->full_name = kstrdup(full_name, GFP_KERNEL);
        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)
{
        if (ce->action == OF_RECONFIG_ATTACH_NODE &&
            of_node_check_flag(ce->np, OF_OVERLAY)) {
                if (kref_read(&ce->np->kobj.kref) > 1) {
                        pr_err("ERROR: memory leak, expected refcount 1 instead of %d, of_node_get()/of_node_put() unbalanced - destroy cset entry: attach overlay node %pOF\n",
                               kref_read(&ce->np->kobj.kref), ce->np);
                } else {
                        of_node_set_flag(ce->np, OF_OVERLAY_FREE_CSET);
                }
        }

        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("cset<%p> %-15s %pOF/%s\n", ce, action_names[ce->action],
                        ce->np, ce->prop->name);
                break;
        case OF_RECONFIG_ATTACH_NODE:
        case OF_RECONFIG_DETACH_NODE:
                pr_debug("cset<%p> %-15s %pOF\n", ce, action_names[ce->action],
                        ce->np);
                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;
                /* update was used but original property did not exist */
                if (!rce->prop) {
                        rce->action = OF_RECONFIG_REMOVE_PROPERTY;
                        rce->prop = ce->prop;
                }
                break;
        }
}

static int __of_changeset_entry_notify(struct of_changeset_entry *ce,
                bool revert)
{
        struct of_reconfig_data rd;
        struct of_changeset_entry ce_inverted;
        int ret = 0;

        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("invalid devicetree changeset action: %i\n",
                        (int)ce->action);
                ret = -EINVAL;
        }

        if (ret)
                pr_err("changeset notifier error @%pOF\n", ce->np);
        return ret;
}

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("changeset: add_property failed @%pOF/%s\n",
                                ce->np,
                                ce->prop->name);
                        break;
                }
                break;
        case OF_RECONFIG_REMOVE_PROPERTY:
                ret = __of_remove_property(ce->np, ce->prop);
                if (ret) {
                        pr_err("changeset: remove_property failed @%pOF/%s\n",
                                ce->np,
                                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("changeset: update_property failed @%pOF/%s\n",
                                ce->np,
                                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);
}
EXPORT_SYMBOL_GPL(of_changeset_init);

/**
 * 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);
}
EXPORT_SYMBOL_GPL(of_changeset_destroy);

/*
 * Apply the changeset entries in @ocs.
 * If apply fails, an attempt is made to revert the entries that were
 * successfully applied.
 *
 * If multiple revert errors occur then only the final revert error is reported.
 *
 * Returns 0 on success, a negative error value in case of an error.
 * If a revert error occurs, it is returned in *ret_revert.
 */
int __of_changeset_apply_entries(struct of_changeset *ocs, int *ret_revert)
{
        struct of_changeset_entry *ce;
        int ret, ret_tmp;

        pr_debug("changeset: applying...\n");
        list_for_each_entry(ce, &ocs->entries, node) {
                ret = __of_changeset_entry_apply(ce);
                if (ret) {
                        pr_err("Error applying changeset (%d)\n", ret);
                        list_for_each_entry_continue_reverse(ce, &ocs->entries,
                                                             node) {
                                ret_tmp = __of_changeset_entry_revert(ce);
                                if (ret_tmp)
                                        *ret_revert = ret_tmp;
                        }
                        return ret;
                }
        }

        return 0;
}

/*
 * Returns 0 on success, a negative error value in case of an error.
 *
 * If multiple changeset entry notification errors occur then only the
 * final notification error is reported.
 */
int __of_changeset_apply_notify(struct of_changeset *ocs)
{
        struct of_changeset_entry *ce;
        int ret = 0, ret_tmp;

        pr_debug("changeset: emitting notifiers.\n");

        /* drop the global lock while emitting notifiers */
        mutex_unlock(&of_mutex);
        list_for_each_entry(ce, &ocs->entries, node) {
                ret_tmp = __of_changeset_entry_notify(ce, 0);
                if (ret_tmp)
                        ret = ret_tmp;
        }
        mutex_lock(&of_mutex);
        pr_debug("changeset: notifiers sent.\n");

        return ret;
}

/*
 * Returns 0 on success, a negative error value in case of an error.
 *
 * If a changeset entry apply fails, an attempt is made to revert any
 * previous entries in the changeset.  If any of the reverts fails,
 * that failure is not reported.  Thus the state of the device tree
 * is unknown if an apply error occurs.
 */
static int __of_changeset_apply(struct of_changeset *ocs)
{
        int ret, ret_revert = 0;

        ret = __of_changeset_apply_entries(ocs, &ret_revert);
        if (!ret)
                ret = __of_changeset_apply_notify(ocs);

        return ret;
}

/**
 * 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
 * success, 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)
{
        int ret;

        mutex_lock(&of_mutex);
        ret = __of_changeset_apply(ocs);
        mutex_unlock(&of_mutex);

        return ret;
}
EXPORT_SYMBOL_GPL(of_changeset_apply);

/*
 * Revert the changeset entries in @ocs.
 * If revert fails, an attempt is made to re-apply the entries that were
 * successfully removed.
 *
 * If multiple re-apply errors occur then only the final apply error is
 * reported.
 *
 * Returns 0 on success, a negative error value in case of an error.
 * If an apply error occurs, it is returned in *ret_apply.
 */
int __of_changeset_revert_entries(struct of_changeset *ocs, int *ret_apply)
{
        struct of_changeset_entry *ce;
        int ret, ret_tmp;

        pr_debug("changeset: reverting...\n");
        list_for_each_entry_reverse(ce, &ocs->entries, node) {
                ret = __of_changeset_entry_revert(ce);
                if (ret) {
                        pr_err("Error reverting changeset (%d)\n", ret);
                        list_for_each_entry_continue(ce, &ocs->entries, node) {
                                ret_tmp = __of_changeset_entry_apply(ce);
                                if (ret_tmp)
                                        *ret_apply = ret_tmp;
                        }
                        return ret;
                }
        }

        return 0;
}

/*
 * If multiple changeset entry notification errors occur then only the
 * final notification error is reported.
 */
int __of_changeset_revert_notify(struct of_changeset *ocs)
{
        struct of_changeset_entry *ce;
        int ret = 0, ret_tmp;

        pr_debug("changeset: emitting notifiers.\n");

        /* drop the global lock while emitting notifiers */
        mutex_unlock(&of_mutex);
        list_for_each_entry_reverse(ce, &ocs->entries, node) {
                ret_tmp = __of_changeset_entry_notify(ce, 1);
                if (ret_tmp)
                        ret = ret_tmp;
        }
        mutex_lock(&of_mutex);
        pr_debug("changeset: notifiers sent.\n");

        return ret;
}

static int __of_changeset_revert(struct of_changeset *ocs)
{
        int ret, ret_reply;

        ret_reply = 0;
        ret = __of_changeset_revert_entries(ocs, &ret_reply);

        if (!ret)
                ret = __of_changeset_revert_notify(ocs);

        return ret;
}

/**
 * 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)
{
        int ret;

        mutex_lock(&of_mutex);
        ret = __of_changeset_revert(ocs);
        mutex_unlock(&of_mutex);

        return ret;
}
EXPORT_SYMBOL_GPL(of_changeset_revert);

/**
 * of_changeset_action - Add an action to the tail of the changeset list
 *
 * @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)
                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;
}
EXPORT_SYMBOL_GPL(of_changeset_action);