/*
 * Functions for dealing with DT resolution
 *
 * 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: resolver: " 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 "of_private.h"

/* illegal phandle value (set when unresolved) */
#define OF_PHANDLE_ILLEGAL      0xdeadbeef

static phandle live_tree_max_phandle(void)
{
        struct device_node *node;
        phandle phandle;
        unsigned long flags;

        raw_spin_lock_irqsave(&devtree_lock, flags);
        phandle = 0;
        for_each_of_allnodes(node) {
                if (node->phandle != OF_PHANDLE_ILLEGAL &&
                                node->phandle > phandle)
                        phandle = node->phandle;
        }
        raw_spin_unlock_irqrestore(&devtree_lock, flags);

        return phandle;
}

static void adjust_overlay_phandles(struct device_node *overlay,
                int phandle_delta)
{
        struct device_node *child;
        struct property *prop;
        phandle phandle;

        /* adjust node's phandle in node */
        if (overlay->phandle != 0 && overlay->phandle != OF_PHANDLE_ILLEGAL)
                overlay->phandle += phandle_delta;

        /* copy adjusted phandle into *phandle properties */
        for_each_property_of_node(overlay, prop) {

                if (of_prop_cmp(prop->name, "phandle") &&
                    of_prop_cmp(prop->name, "linux,phandle"))
                        continue;

                if (prop->length < 4)
                        continue;

                phandle = be32_to_cpup(prop->value);
                if (phandle == OF_PHANDLE_ILLEGAL)
                        continue;

                *(__be32 *)prop->value = cpu_to_be32(overlay->phandle);
        }

        for_each_child_of_node(overlay, child)
                adjust_overlay_phandles(child, phandle_delta);
}

static int update_usages_of_a_phandle_reference(struct device_node *overlay,
                struct property *prop_fixup, phandle phandle)
{
        struct device_node *refnode;
        struct property *prop;
        char *value, *cur, *end, *node_path, *prop_name, *s;
        int offset, len;
        int err = 0;

        value = kmalloc(prop_fixup->length, GFP_KERNEL);
        if (!value)
                return -ENOMEM;
        memcpy(value, prop_fixup->value, prop_fixup->length);

        /* prop_fixup contains a list of tuples of path:property_name:offset */
        end = value + prop_fixup->length;
        for (cur = value; cur < end; cur += len + 1) {
                len = strlen(cur);

                node_path = cur;
                s = strchr(cur, ':');
                if (!s) {
                        err = -EINVAL;
                        goto err_fail;
                }
                *s++ = '\0';

                prop_name = s;
                s = strchr(s, ':');
                if (!s) {
                        err = -EINVAL;
                        goto err_fail;
                }
                *s++ = '\0';

                err = kstrtoint(s, 10, &offset);
                if (err)
                        goto err_fail;

                refnode = __of_find_node_by_full_path(of_node_get(overlay), node_path);
                if (!refnode)
                        continue;

                for_each_property_of_node(refnode, prop) {
                        if (!of_prop_cmp(prop->name, prop_name))
                                break;
                }
                of_node_put(refnode);

                if (!prop) {
                        err = -ENOENT;
                        goto err_fail;
                }

                *(__be32 *)(prop->value + offset) = cpu_to_be32(phandle);
        }

err_fail:
        kfree(value);
        return err;
}

/* compare nodes taking into account that 'name' strips out the @ part */
static int node_name_cmp(const struct device_node *dn1,
                const struct device_node *dn2)
{
        const char *n1 = kbasename(dn1->full_name);
        const char *n2 = kbasename(dn2->full_name);

        return of_node_cmp(n1, n2);
}

/*
 * Adjust the local phandle references by the given phandle delta.
 *
 * Subtree @local_fixups, which is overlay node __local_fixups__,
 * mirrors the fragment node structure at the root of the overlay.
 *
 * For each property in the fragments that contains a phandle reference,
 * @local_fixups has a property of the same name that contains a list
 * of offsets of the phandle reference(s) within the respective property
 * value(s).  The values at these offsets will be fixed up.
 */
static int adjust_local_phandle_references(struct device_node *local_fixups,
                struct device_node *overlay, int phandle_delta)
{
        struct device_node *child, *overlay_child;
        struct property *prop_fix, *prop;
        int err, i, count;
        unsigned int off;
        phandle phandle;

        if (!local_fixups)
                return 0;

        for_each_property_of_node(local_fixups, prop_fix) {

                /* skip properties added automatically */
                if (!of_prop_cmp(prop_fix->name, "name") ||
                    !of_prop_cmp(prop_fix->name, "phandle") ||
                    !of_prop_cmp(prop_fix->name, "linux,phandle"))
                        continue;

                if ((prop_fix->length % 4) != 0 || prop_fix->length == 0)
                        return -EINVAL;
                count = prop_fix->length / sizeof(__be32);

                for_each_property_of_node(overlay, prop) {
                        if (!of_prop_cmp(prop->name, prop_fix->name))
                                break;
                }

                if (!prop)
                        return -EINVAL;

                for (i = 0; i < count; i++) {
                        off = be32_to_cpu(((__be32 *)prop_fix->value)[i]);
                        if ((off + 4) > prop->length)
                                return -EINVAL;

                        phandle = be32_to_cpu(*(__be32 *)(prop->value + off));
                        phandle += phandle_delta;
                        *(__be32 *)(prop->value + off) = cpu_to_be32(phandle);
                }
        }

        /*
         * These nested loops recurse down two subtrees in parallel, where the
         * node names in the two subtrees match.
         *
         * The roots of the subtrees are the overlay's __local_fixups__ node
         * and the overlay's root node.
         */
        for_each_child_of_node(local_fixups, child) {

                for_each_child_of_node(overlay, overlay_child)
                        if (!node_name_cmp(child, overlay_child))
                                break;

                if (!overlay_child)
                        return -EINVAL;

                err = adjust_local_phandle_references(child, overlay_child,
                                phandle_delta);
                if (err)
                        return err;
        }

        return 0;
}

/**
 * of_resolve_phandles - Relocate and resolve overlay against live tree
 *
 * @overlay:    Pointer to devicetree overlay to relocate and resolve
 *
 * Modify (relocate) values of local phandles in @overlay to a range that
 * does not conflict with the live expanded devicetree.  Update references
 * to the local phandles in @overlay.  Update (resolve) phandle references
 * in @overlay that refer to the live expanded devicetree.
 *
 * Phandle values in the live tree are in the range of
 * 1 .. live_tree_max_phandle().  The range of phandle values in the overlay
 * also begin with at 1.  Adjust the phandle values in the overlay to begin
 * at live_tree_max_phandle() + 1.  Update references to the phandles to
 * the adjusted phandle values.
 *
 * The name of each property in the "__fixups__" node in the overlay matches
 * the name of a symbol (a label) in the live tree.  The values of each
 * property in the "__fixups__" node is a list of the property values in the
 * overlay that need to be updated to contain the phandle reference
 * corresponding to that symbol in the live tree.  Update the references in
 * the overlay with the phandle values in the live tree.
 *
 * @overlay must be detached.
 *
 * Resolving and applying @overlay to the live expanded devicetree must be
 * protected by a mechanism to ensure that multiple overlays are processed
 * in a single threaded manner so that multiple overlays will not relocate
 * phandles to overlapping ranges.  The mechanism to enforce this is not
 * yet implemented.
 *
 * Return: %0 on success or a negative error value on error.
 */
int of_resolve_phandles(struct device_node *overlay)
{
        struct device_node *child, *local_fixups, *refnode;
        struct device_node *tree_symbols, *overlay_fixups;
        struct property *prop;
        const char *refpath;
        phandle phandle, phandle_delta;
        int err;

        tree_symbols = NULL;

        if (!overlay) {
                pr_err("null overlay\n");
                err = -EINVAL;
                goto out;
        }
        if (!of_node_check_flag(overlay, OF_DETACHED)) {
                pr_err("overlay not detached\n");
                err = -EINVAL;
                goto out;
        }

        phandle_delta = live_tree_max_phandle() + 1;
        adjust_overlay_phandles(overlay, phandle_delta);

        for_each_child_of_node(overlay, local_fixups)
                if (!of_node_cmp(local_fixups->name, "__local_fixups__"))
                        break;

        err = adjust_local_phandle_references(local_fixups, overlay, phandle_delta);
        if (err)
                goto out;

        overlay_fixups = NULL;

        for_each_child_of_node(overlay, child) {
                if (!of_node_cmp(child->name, "__fixups__"))
                        overlay_fixups = child;
        }

        if (!overlay_fixups) {
                err = 0;
                goto out;
        }

        tree_symbols = of_find_node_by_path("/__symbols__");
        if (!tree_symbols) {
                pr_err("no symbols in root of device tree.\n");
                err = -EINVAL;
                goto out;
        }

        for_each_property_of_node(overlay_fixups, prop) {

                /* skip properties added automatically */
                if (!of_prop_cmp(prop->name, "name"))
                        continue;

                err = of_property_read_string(tree_symbols,
                                prop->name, &refpath);
                if (err)
                        goto out;

                refnode = of_find_node_by_path(refpath);
                if (!refnode) {
                        err = -ENOENT;
                        goto out;
                }

                phandle = refnode->phandle;
                of_node_put(refnode);

                err = update_usages_of_a_phandle_reference(overlay, prop, phandle);
                if (err)
                        break;
        }

out:
        if (err)
                pr_err("overlay phandle fixup failed: %d\n", err);
        of_node_put(tree_symbols);

        return err;
}
EXPORT_SYMBOL_GPL(of_resolve_phandles);