// SPDX-License-Identifier: GPL-2.0+
/*
 * Virtual concat MTD device driver
 *
 * Copyright (C) 2018 Bernhard Frauendienst
 * Author: Bernhard Frauendienst <kernel@nospam.obeliks.de>
 */

#include <linux/device.h>
#include <linux/mtd/mtd.h>
#include "mtdcore.h"
#include <linux/mtd/partitions.h>
#include <linux/of.h>
#include <linux/of_platform.h>
#include <linux/slab.h>
#include <linux/mtd/concat.h>

#define CONCAT_PROP "part-concat-next"
#define CONCAT_POSTFIX "concat"
#define MIN_DEV_PER_CONCAT 1

static LIST_HEAD(concat_node_list);

/**
 * struct mtd_virt_concat_node - components of a concatenation
 * @head: List handle
 * @count: Number of nodes
 * @nodes: Pointer to the nodes (partitions) to concatenate
 * @concat: Concatenation container
 */
struct mtd_virt_concat_node {
        struct list_head head;
        unsigned int count;
        struct mtd_concat *concat;
        struct device_node *nodes[] __counted_by(count);
};

/**
 * mtd_is_part_concat - Check if the device is already part
 *                       of a concatenated device
 * @dev:        pointer to 'device_node'
 *
 * Return: true if the device is already part of a concatenation,
 *         false otherwise.
 */
static bool mtd_is_part_concat(struct device_node *dev)
{
        struct mtd_virt_concat_node *item;
        int idx;

        list_for_each_entry(item, &concat_node_list, head) {
                for (idx = 0; idx < item->count; idx++) {
                        if (item->nodes[idx] == dev)
                                return true;
                }
        }
        return false;
}

static void mtd_virt_concat_put_mtd_devices(struct mtd_concat *concat)
{
        int i;

        for (i = 0; i < concat->num_subdev; i++)
                put_mtd_device(concat->subdev[i]);
}

void mtd_virt_concat_destroy_joins(void)
{
        struct mtd_virt_concat_node *item, *tmp;
        struct mtd_info *mtd;

        list_for_each_entry_safe(item, tmp, &concat_node_list, head) {
                mtd = &item->concat->mtd;
                if (item->concat) {
                        mtd_device_unregister(mtd);
                        kfree(mtd->name);
                        mtd_virt_concat_put_mtd_devices(item->concat);
                        mtd_concat_destroy(mtd);
                }
        }
}

/**
 * mtd_virt_concat_destroy - Destroy the concat that includes the mtd object
 * @mtd:        pointer to 'mtd_info'
 *
 * Return: 0 on success, -error otherwise.
 */
int mtd_virt_concat_destroy(struct mtd_info *mtd)
{
        struct mtd_info *child, *master = mtd_get_master(mtd);
        struct mtd_virt_concat_node *item, *tmp;
        struct mtd_concat *concat;
        int idx, ret = 0;
        bool is_mtd_found;

        list_for_each_entry_safe(item, tmp, &concat_node_list, head) {
                is_mtd_found = false;

                /* Find the concat item that hold the mtd device */
                for (idx = 0; idx < item->count; idx++) {
                        if (item->nodes[idx] == mtd->dev.of_node) {
                                is_mtd_found = true;
                                break;
                        }
                }
                if (!is_mtd_found)
                        continue;
                concat = item->concat;

                /*
                 * Since this concatenated device is being removed, retrieve
                 * all MTD devices that are part of it and register them
                 * individually.
                 */
                for (idx = 0; idx < concat->num_subdev; idx++) {
                        child = concat->subdev[idx];
                        if (child->dev.of_node != mtd->dev.of_node) {
                                ret = add_mtd_device(child);
                                if (ret)
                                        goto out;
                        }
                }
                /* Destroy the concat */
                if (concat->mtd.name) {
                        del_mtd_device(&concat->mtd);
                        kfree(concat->mtd.name);
                        mtd_virt_concat_put_mtd_devices(item->concat);
                        mtd_concat_destroy(&concat->mtd);
                }

                for (idx = 0; idx < item->count; idx++)
                        of_node_put(item->nodes[idx]);

                kfree(item);
        }
        return 0;
out:
        mutex_lock(&master->master.partitions_lock);
        list_del(&child->part.node);
        mutex_unlock(&master->master.partitions_lock);
        kfree(mtd->name);
        kfree(mtd);

        return ret;
}

/**
 * mtd_virt_concat_create_item - Create a concat item
 * @parts:        pointer to 'device_node'
 * @count:        number of mtd devices that make up
 *                the concatenated device.
 *
 * Return: 0 on success, -error otherwise.
 */
static int mtd_virt_concat_create_item(struct device_node *parts,
                                       unsigned int count)
{
        struct mtd_virt_concat_node *item;
        struct mtd_concat *concat;
        int i;

        for (i = 0; i < (count - 1); i++) {
                if (mtd_is_part_concat(of_parse_phandle(parts, CONCAT_PROP, i)))
                        return 0;
        }

        item = kzalloc_flex(*item, nodes, count, GFP_KERNEL);
        if (!item)
                return -ENOMEM;

        item->count = count;

        /*
         * The partition in which "part-concat-next" property
         * is defined is the first device in the list of concat
         * devices.
         */
        item->nodes[0] = parts;

        for (i = 1; i < count; i++)
                item->nodes[i] = of_parse_phandle(parts, CONCAT_PROP, (i - 1));

        concat = kzalloc_flex(*concat, subdev, count, GFP_KERNEL);
        if (!concat) {
                kfree(item);
                return -ENOMEM;
        }

        item->concat = concat;

        list_add_tail(&item->head, &concat_node_list);

        return 0;
}

void mtd_virt_concat_destroy_items(void)
{
        struct mtd_virt_concat_node *item, *temp;
        int i;

        list_for_each_entry_safe(item, temp, &concat_node_list, head) {
                for (i = 0; i < item->count; i++)
                        of_node_put(item->nodes[i]);

                kfree(item);
        }
}

/**
 * mtd_virt_concat_add - Add a mtd device to the concat list
 * @mtd:        pointer to 'mtd_info'
 *
 * Return: true on success, false otherwise.
 */
bool mtd_virt_concat_add(struct mtd_info *mtd)
{
        struct mtd_virt_concat_node *item;
        struct mtd_concat *concat;
        int idx;

        list_for_each_entry(item, &concat_node_list, head) {
                concat = item->concat;
                for (idx = 0; idx < item->count; idx++) {
                        if (item->nodes[idx] == mtd->dev.of_node) {
                                concat->subdev[concat->num_subdev++] = mtd;
                                return true;
                        }
                }
        }
        return false;
}

/**
 * mtd_virt_concat_node_create - List all the concatenations found in DT
 *
 * Return: 0 on success, -error otherwise.
 */
int mtd_virt_concat_node_create(void)
{
        struct device_node *parts = NULL;
        int ret = 0, count = 0;

        /* List all the concatenations found in DT */
        do {
                parts = of_find_node_with_property(parts, CONCAT_PROP);
                if (!of_device_is_available(parts))
                        continue;

                if (mtd_is_part_concat(parts))
                        continue;

                count = of_count_phandle_with_args(parts, CONCAT_PROP, NULL);
                if (count < MIN_DEV_PER_CONCAT)
                        continue;

                /*
                 * The partition in which "part-concat-next" property is defined
                 * is also part of the concat device, so increament count by 1.
                 */
                count++;

                ret = mtd_virt_concat_create_item(parts, count);
                if (ret) {
                        of_node_put(parts);
                        goto destroy_items;
                }
        } while (parts);

        return ret;

destroy_items:
        mtd_virt_concat_destroy_items();

        return ret;
}

/**
 * mtd_virt_concat_create_join - Create and register the concatenated
 *                                 MTD device.
 *
 * Return: 0 on success, -error otherwise.
 */
int mtd_virt_concat_create_join(void)
{
        struct mtd_virt_concat_node *item;
        struct mtd_concat *concat;
        struct mtd_info *mtd;
        ssize_t name_sz;
        int ret, idx;
        char *name;

        list_for_each_entry(item, &concat_node_list, head) {
                concat = item->concat;
                /*
                 * Check if item->count != concat->num_subdev, it indicates
                 * that the MTD information for all devices included in the
                 * concatenation are not handy, concat MTD device can't be
                 * created hence switch to next concat device.
                 */
                if (item->count != concat->num_subdev) {
                        continue;
                } else {
                        /* Calculate the legth of the name of the virtual device */
                        for (idx = 0, name_sz = 0; idx < concat->num_subdev; idx++)
                                name_sz += (strlen(concat->subdev[idx]->name) + 1);
                        name_sz += strlen(CONCAT_POSTFIX);
                        name = kmalloc(name_sz + 1, GFP_KERNEL);
                        if (!name) {
                                mtd_virt_concat_put_mtd_devices(concat);
                                return -ENOMEM;
                        }

                        ret = 0;
                        for (idx = 0; idx < concat->num_subdev; idx++) {
                                ret += sprintf((name + ret), "%s-",
                                               concat->subdev[idx]->name);
                        }
                        sprintf((name + ret), CONCAT_POSTFIX);

                        if (concat->mtd.name) {
                                ret = memcmp(concat->mtd.name, name, name_sz);
                                if (ret == 0) {
                                        kfree(name);
                                        continue;
                                }
                        }
                        mtd = mtd_concat_create(concat->subdev, concat->num_subdev, name);
                        if (!mtd) {
                                kfree(name);
                                return -ENXIO;
                        }
                        concat->mtd = *mtd;
                        /* Arbitrary set the first device as parent */
                        concat->mtd.dev.parent = concat->subdev[0]->dev.parent;
                        concat->mtd.dev = concat->subdev[0]->dev;

                        /* Add the mtd device */
                        ret = add_mtd_device(&concat->mtd);
                        if (ret)
                                goto destroy_concat;
                }
        }

        return 0;

destroy_concat:
        mtd_concat_destroy(mtd);

        return ret;
}