/*
 * 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.
 */
#undef DEBUG
#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/string.h>
#include <linux/slab.h>
#include <linux/err.h>
#include <linux/idr.h>

#include "of_private.h"

/**
 * struct of_overlay_info - Holds a single overlay info
 * @target:     target of the overlay operation
 * @overlay:    pointer to the overlay contents node
 *
 * Holds a single overlay state, including all the overlay logs &
 * records.
 */
struct of_overlay_info {
        struct device_node *target;
        struct device_node *overlay;
};

/**
 * struct of_overlay - Holds a complete overlay transaction
 * @node:       List on which we are located
 * @count:      Count of ovinfo structures
 * @ovinfo_tab: Overlay info table (count sized)
 * @cset:       Changeset to be used
 *
 * Holds a complete overlay transaction
 */
struct of_overlay {
        int id;
        struct list_head node;
        int count;
        struct of_overlay_info *ovinfo_tab;
        struct of_changeset cset;
};

static int of_overlay_apply_one(struct of_overlay *ov,
                struct device_node *target, const struct device_node *overlay);

static int of_overlay_apply_single_property(struct of_overlay *ov,
                struct device_node *target, struct property *prop)
{
        struct property *propn, *tprop;

        /* NOTE: Multiple changes of single properties not supported */
        tprop = of_find_property(target, prop->name, NULL);

        /* special properties are not meant to be updated (silent NOP) */
        if (of_prop_cmp(prop->name, "name") == 0 ||
            of_prop_cmp(prop->name, "phandle") == 0 ||
            of_prop_cmp(prop->name, "linux,phandle") == 0)
                return 0;

        propn = __of_prop_dup(prop, GFP_KERNEL);
        if (propn == NULL)
                return -ENOMEM;

        /* not found? add */
        if (tprop == NULL)
                return of_changeset_add_property(&ov->cset, target, propn);

        /* found? update */
        return of_changeset_update_property(&ov->cset, target, propn);
}

static int of_overlay_apply_single_device_node(struct of_overlay *ov,
                struct device_node *target, struct device_node *child)
{
        const char *cname;
        struct device_node *tchild;
        int ret = 0;

        cname = kbasename(child->full_name);
        if (cname == NULL)
                return -ENOMEM;

        /* NOTE: Multiple mods of created nodes not supported */
        tchild = of_get_child_by_name(target, cname);
        if (tchild != NULL) {
                /* apply overlay recursively */
                ret = of_overlay_apply_one(ov, tchild, child);
                of_node_put(tchild);
        } else {
                /* create empty tree as a target */
                tchild = __of_node_dup(child, "%s/%s", target->full_name, cname);
                if (!tchild)
                        return -ENOMEM;

                /* point to parent */
                tchild->parent = target;

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

                ret = of_overlay_apply_one(ov, tchild, child);
                if (ret)
                        return ret;
        }

        return ret;
}

/*
 * Apply a single overlay node recursively.
 *
 * Note that the in case of an error the target node is left
 * in a inconsistent state. Error recovery should be performed
 * by using the changeset.
 */
static int of_overlay_apply_one(struct of_overlay *ov,
                struct device_node *target, const struct device_node *overlay)
{
        struct device_node *child;
        struct property *prop;
        int ret;

        for_each_property_of_node(overlay, prop) {
                ret = of_overlay_apply_single_property(ov, target, prop);
                if (ret) {
                        pr_err("%s: Failed to apply prop @%s/%s\n",
                                __func__, target->full_name, prop->name);
                        return ret;
                }
        }

        for_each_child_of_node(overlay, child) {
                ret = of_overlay_apply_single_device_node(ov, target, child);
                if (ret != 0) {
                        pr_err("%s: Failed to apply single node @%s/%s\n",
                                        __func__, target->full_name,
                                        child->name);
                        return ret;
                }
        }

        return 0;
}

/**
 * of_overlay_apply() - Apply @count overlays pointed at by @ovinfo_tab
 * @ov:         Overlay to apply
 *
 * Applies the overlays given, while handling all error conditions
 * appropriately. Either the operation succeeds, or if it fails the
 * live tree is reverted to the state before the attempt.
 * Returns 0, or an error if the overlay attempt failed.
 */
static int of_overlay_apply(struct of_overlay *ov)
{
        int i, err;

        /* first we apply the overlays atomically */
        for (i = 0; i < ov->count; i++) {
                struct of_overlay_info *ovinfo = &ov->ovinfo_tab[i];

                err = of_overlay_apply_one(ov, ovinfo->target, ovinfo->overlay);
                if (err != 0) {
                        pr_err("%s: overlay failed '%s'\n",
                                __func__, ovinfo->target->full_name);
                        return err;
                }
        }

        return 0;
}

/*
 * Find the target node using a number of different strategies
 * in order of preference
 *
 * "target" property containing the phandle of the target
 * "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;

        /* first try to go by using the target as a phandle */
        ret = of_property_read_u32(info_node, "target", &val);
        if (ret == 0)
                return of_find_node_by_phandle(val);

        /* now try to locate by path */
        ret = of_property_read_string(info_node, "target-path", &path);
        if (ret == 0)
                return of_find_node_by_path(path);

        pr_err("%s: Failed to find target for node %p (%s)\n", __func__,
                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 of_overlay *ov,
                struct device_node *info_node, struct of_overlay_info *ovinfo)
{
        ovinfo->overlay = of_get_child_by_name(info_node, "__overlay__");
        if (ovinfo->overlay == NULL)
                goto err_fail;

        ovinfo->target = find_target_node(info_node);
        if (ovinfo->target == NULL)
                goto err_fail;

        return 0;

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

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

/**
 * of_build_overlay_info() - Build an overlay info array
 * @ov          Overlay to build
 * @tree:       Device node containing all the overlays
 *
 * Helper function that given a tree containing overlay information,
 * allocates and builds an overlay info array containing it, ready
 * for use using of_overlay_apply.
 *
 * Returns 0 on success with the @cntp @ovinfop pointers valid,
 * while on error a negative error value is returned.
 */
static int of_build_overlay_info(struct of_overlay *ov,
                struct device_node *tree)
{
        struct device_node *node;
        struct of_overlay_info *ovinfo;
        int cnt, err;

        /* worst case; every child is a node */
        cnt = 0;
        for_each_child_of_node(tree, node)
                cnt++;

        ovinfo = kcalloc(cnt, sizeof(*ovinfo), GFP_KERNEL);
        if (ovinfo == NULL)
                return -ENOMEM;

        cnt = 0;
        for_each_child_of_node(tree, node) {
                memset(&ovinfo[cnt], 0, sizeof(*ovinfo));
                err = of_fill_overlay_info(ov, node, &ovinfo[cnt]);
                if (err == 0)
                        cnt++;
        }

        /* if nothing filled, return error */
        if (cnt == 0) {
                kfree(ovinfo);
                return -ENODEV;
        }

        ov->count = cnt;
        ov->ovinfo_tab = ovinfo;

        return 0;
}

/**
 * of_free_overlay_info() - Free an overlay info array
 * @ov          Overlay to free the overlay info from
 * @ovinfo_tab: Array of overlay_info's to free
 *
 * Releases the memory of a previously allocated ovinfo array
 * by of_build_overlay_info.
 * Returns 0, or an error if the arguments are bogus.
 */
static int of_free_overlay_info(struct of_overlay *ov)
{
        struct of_overlay_info *ovinfo;
        int i;

        /* do it in reverse */
        for (i = ov->count - 1; i >= 0; i--) {
                ovinfo = &ov->ovinfo_tab[i];

                of_node_put(ovinfo->target);
                of_node_put(ovinfo->overlay);
        }
        kfree(ov->ovinfo_tab);

        return 0;
}

static LIST_HEAD(ov_list);
static DEFINE_IDR(ov_idr);

/**
 * of_overlay_create() - Create and apply an overlay
 * @tree:       Device node containing all the overlays
 *
 * Creates and applies an overlay while also keeping track
 * of the overlay in a list. This list can be used to prevent
 * illegal overlay removals.
 *
 * Returns the id of the created overlay, or a negative error number
 */
int of_overlay_create(struct device_node *tree)
{
        struct of_overlay *ov;
        int err, id;

        /* allocate the overlay structure */
        ov = kzalloc(sizeof(*ov), GFP_KERNEL);
        if (ov == NULL)
                return -ENOMEM;
        ov->id = -1;

        INIT_LIST_HEAD(&ov->node);

        of_changeset_init(&ov->cset);

        mutex_lock(&of_mutex);

        id = idr_alloc(&ov_idr, ov, 0, 0, GFP_KERNEL);
        if (id < 0) {
                pr_err("%s: idr_alloc() failed for tree@%s\n",
                                __func__, tree->full_name);
                err = id;
                goto err_destroy_trans;
        }
        ov->id = id;

        /* build the overlay info structures */
        err = of_build_overlay_info(ov, tree);
        if (err) {
                pr_err("%s: of_build_overlay_info() failed for tree@%s\n",
                                __func__, tree->full_name);
                goto err_free_idr;
        }

        /* apply the overlay */
        err = of_overlay_apply(ov);
        if (err) {
                pr_err("%s: of_overlay_apply() failed for tree@%s\n",
                                __func__, tree->full_name);
                goto err_abort_trans;
        }

        /* apply the changeset */
        err = of_changeset_apply(&ov->cset);
        if (err) {
                pr_err("%s: of_changeset_apply() failed for tree@%s\n",
                                __func__, tree->full_name);
                goto err_revert_overlay;
        }

        /* add to the tail of the overlay list */
        list_add_tail(&ov->node, &ov_list);

        mutex_unlock(&of_mutex);

        return id;

err_revert_overlay:
err_abort_trans:
        of_free_overlay_info(ov);
err_free_idr:
        idr_remove(&ov_idr, ov->id);
err_destroy_trans:
        of_changeset_destroy(&ov->cset);
        kfree(ov);
        mutex_unlock(&of_mutex);

        return err;
}
EXPORT_SYMBOL_GPL(of_overlay_create);

/* check whether the given node, lies under the given tree */
static int overlay_subtree_check(struct device_node *tree,
                struct device_node *dn)
{
        struct device_node *child;

        /* match? */
        if (tree == dn)
                return 1;

        for_each_child_of_node(tree, child) {
                if (overlay_subtree_check(child, dn))
                        return 1;
        }

        return 0;
}

/* check whether this overlay is the topmost */
static int overlay_is_topmost(struct of_overlay *ov, struct device_node *dn)
{
        struct of_overlay *ovt;
        struct of_changeset_entry *ce;

        list_for_each_entry_reverse(ovt, &ov_list, node) {
                /* if we hit ourselves, we're done */
                if (ovt == ov)
                        break;

                /* check against each subtree affected by this overlay */
                list_for_each_entry(ce, &ovt->cset.entries, node) {
                        if (overlay_subtree_check(ce->np, dn)) {
                                pr_err("%s: #%d clashes #%d @%s\n",
                                        __func__, ov->id, ovt->id,
                                        dn->full_name);
                                return 0;
                        }
                }
        }

        /* overlay is topmost */
        return 1;
}

/*
 * 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 of_overlay *ov)
{
        struct of_changeset_entry *ce;

        list_for_each_entry(ce, &ov->cset.entries, node) {
                if (!overlay_is_topmost(ov, ce->np)) {
                        pr_err("%s: overlay #%d is not topmost\n",
                                        __func__, ov->id);
                        return 0;
                }
        }

        return 1;
}

/**
 * of_overlay_destroy() - Removes an overlay
 * @id: Overlay id number returned by a previous call to of_overlay_create
 *
 * Removes an overlay if it is permissible.
 *
 * Returns 0 on success, or a negative error number
 */
int of_overlay_destroy(int id)
{
        struct of_overlay *ov;
        int err;

        mutex_lock(&of_mutex);

        ov = idr_find(&ov_idr, id);
        if (ov == NULL) {
                err = -ENODEV;
                pr_err("%s: Could not find overlay #%d\n",
                                __func__, id);
                goto out;
        }

        /* check whether the overlay is safe to remove */
        if (!overlay_removal_is_ok(ov)) {
                err = -EBUSY;
                pr_err("%s: removal check failed for overlay #%d\n",
                                __func__, id);
                goto out;
        }


        list_del(&ov->node);
        of_changeset_revert(&ov->cset);
        of_free_overlay_info(ov);
        idr_remove(&ov_idr, id);
        of_changeset_destroy(&ov->cset);
        kfree(ov);

        err = 0;

out:
        mutex_unlock(&of_mutex);

        return err;
}
EXPORT_SYMBOL_GPL(of_overlay_destroy);

/**
 * of_overlay_destroy_all() - Removes all overlays from the system
 *
 * Removes all overlays from the system in the correct order.
 *
 * Returns 0 on success, or a negative error number
 */
int of_overlay_destroy_all(void)
{
        struct of_overlay *ov, *ovn;

        mutex_lock(&of_mutex);

        /* the tail of list is guaranteed to be safe to remove */
        list_for_each_entry_safe_reverse(ov, ovn, &ov_list, node) {
                list_del(&ov->node);
                of_changeset_revert(&ov->cset);
                of_free_overlay_info(ov);
                idr_remove(&ov_idr, ov->id);
                kfree(ov);
        }

        mutex_unlock(&of_mutex);

        return 0;
}
EXPORT_SYMBOL_GPL(of_overlay_destroy_all);