dt: add of_alias_scan and of_alias_get_id

[mirror_ubuntu-jammy-kernel.git] / drivers / of / base.c

/*
 * 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/ctype.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/spinlock.h>
#include <linux/slab.h>
#include <linux/proc_fs.h>

/**
 * struct alias_prop - Alias property in 'aliases' node
 * @link:       List node to link the structure in aliases_lookup list
 * @alias:      Alias property name
 * @np:         Pointer to device_node that the alias stands for
 * @id:         Index value from end of alias name
 * @stem:       Alias string without the index
 *
 * The structure represents one alias property of 'aliases' node as
 * an entry in aliases_lookup list.
 */
struct alias_prop {
        struct list_head link;
        const char *alias;
        struct device_node *np;
        int id;
        char stem[0];
};

static LIST_HEAD(aliases_lookup);

struct device_node *allnodes;
struct device_node *of_chosen;
struct device_node *of_aliases;

static DEFINE_MUTEX(of_aliases_mutex);

/* 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\n", 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_property_read_u32_array - Find and read an array of 32 bit integers
 * from a property.
 *
 * @np:         device node from which the property value is to be read.
 * @propname:   name of the property to be searched.
 * @out_value:  pointer to return value, modified only if return value is 0.
 *
 * Search for a property in a device node and read 32-bit value(s) from
 * it. Returns 0 on success, -EINVAL if the property does not exist,
 * -ENODATA if property does not have a value, and -EOVERFLOW if the
 * property data isn't large enough.
 *
 * The out_value is modified only if a valid u32 value can be decoded.
 */
int of_property_read_u32_array(const struct device_node *np,
                               const char *propname, u32 *out_values,
                               size_t sz)
{
        struct property *prop = of_find_property(np, propname, NULL);
        const __be32 *val;

        if (!prop)
                return -EINVAL;
        if (!prop->value)
                return -ENODATA;
        if ((sz * sizeof(*out_values)) > prop->length)
                return -EOVERFLOW;

        val = prop->value;
        while (sz--)
                *out_values++ = be32_to_cpup(val++);
        return 0;
}
EXPORT_SYMBOL_GPL(of_property_read_u32_array);

/**
 * of_property_read_string - Find and read a string from a property
 * @np:         device node from which the property value is to be read.
 * @propname:   name of the property to be searched.
 * @out_string: pointer to null terminated return string, modified only if
 *              return value is 0.
 *
 * Search for a property in a device tree node and retrieve a null
 * terminated string value (pointer to data, not a copy). Returns 0 on
 * success, -EINVAL if the property does not exist, -ENODATA if property
 * does not have a value, and -EILSEQ if the string is not null-terminated
 * within the length of the property data.
 *
 * The out_string pointer is modified only if a valid string can be decoded.
 */
int of_property_read_string(struct device_node *np, const char *propname,
                                const char **out_string)
{
        struct property *prop = of_find_property(np, propname, NULL);
        if (!prop)
                return -EINVAL;
        if (!prop->value)
                return -ENODATA;
        if (strnlen(prop->value, prop->length) >= prop->length)
                return -EILSEQ;
        *out_string = prop->value;
        return 0;
}
EXPORT_SYMBOL_GPL(of_property_read_string);

/**
 * 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\n",
                                 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\n",
                                 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\n",
                                 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\n", __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) */

static void of_alias_add(struct alias_prop *ap, struct device_node *np,
                         int id, const char *stem, int stem_len)
{
        ap->np = np;
        ap->id = id;
        strncpy(ap->stem, stem, stem_len);
        ap->stem[stem_len] = 0;
        list_add_tail(&ap->link, &aliases_lookup);
        pr_debug("adding DT alias:%s: stem=%s id=%i node=%s\n",
                 ap->alias, ap->stem, ap->id, np ? np->full_name : NULL);
}

/**
 * of_alias_scan - Scan all properties of 'aliases' node
 *
 * The function scans all the properties of 'aliases' node and populate
 * the the global lookup table with the properties.  It returns the
 * number of alias_prop found, or error code in error case.
 *
 * @dt_alloc:   An allocator that provides a virtual address to memory
 *              for the resulting tree
 */
void of_alias_scan(void * (*dt_alloc)(u64 size, u64 align))
{
        struct property *pp;

        of_chosen = of_find_node_by_path("/chosen");
        if (of_chosen == NULL)
                of_chosen = of_find_node_by_path("/chosen@0");
        of_aliases = of_find_node_by_path("/aliases");
        if (!of_aliases)
                return;

        for_each_property(pp, of_aliases->properties) {
                const char *start = pp->name;
                const char *end = start + strlen(start);
                struct device_node *np;
                struct alias_prop *ap;
                int id, len;

                /* Skip those we do not want to proceed */
                if (!strcmp(pp->name, "name") ||
                    !strcmp(pp->name, "phandle") ||
                    !strcmp(pp->name, "linux,phandle"))
                        continue;

                np = of_find_node_by_path(pp->value);
                if (!np)
                        continue;

                /* walk the alias backwards to extract the id and work out
                 * the 'stem' string */
                while (isdigit(*(end-1)) && end > start)
                        end--;
                len = end - start;

                if (kstrtoint(end, 10, &id) < 0)
                        continue;

                /* Allocate an alias_prop with enough space for the stem */
                ap = dt_alloc(sizeof(*ap) + len + 1, 4);
                if (!ap)
                        continue;
                ap->alias = start;
                of_alias_add(ap, np, id, start, len);
        }
}

/**
 * of_alias_get_id - Get alias id for the given device_node
 * @np:         Pointer to the given device_node
 * @stem:       Alias stem of the given device_node
 *
 * The function travels the lookup table to get alias id for the given
 * device_node and alias stem.  It returns the alias id if find it.
 */
int of_alias_get_id(struct device_node *np, const char *stem)
{
        struct alias_prop *app;
        int id = -ENODEV;

        mutex_lock(&of_aliases_mutex);
        list_for_each_entry(app, &aliases_lookup, link) {
                if (strcmp(app->stem, stem) != 0)
                        continue;

                if (np == app->np) {
                        id = app->id;
                        break;
                }
        }
        mutex_unlock(&of_aliases_mutex);

        return id;
}
EXPORT_SYMBOL_GPL(of_alias_get_id);