// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright © 2022 Rafał Miłecki <rafal@milecki.pl>
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/mtd/mtd.h>
#include <linux/mtd/partitions.h>
#include <linux/of.h>
#include <linux/slab.h>

#define TPLINK_SAFELOADER_DATA_OFFSET           4
#define TPLINK_SAFELOADER_MAX_PARTS             32

struct safeloader_cmn_header {
        __be32 size;
        uint32_t unused;
} __packed;

static void *mtd_parser_tplink_safeloader_read_table(struct mtd_info *mtd)
{
        struct safeloader_cmn_header hdr;
        struct device_node *np;
        size_t bytes_read;
        size_t size;
        u32 offset;
        char *buf;
        int err;

        np = mtd_get_of_node(mtd);
        if (mtd_is_partition(mtd))
                of_node_get(np);
        else
                np = of_get_child_by_name(np, "partitions");

        if (of_property_read_u32(np, "partitions-table-offset", &offset)) {
                pr_err("Failed to get partitions table offset\n");
                goto err_put;
        }

        err = mtd_read(mtd, offset, sizeof(hdr), &bytes_read, (uint8_t *)&hdr);
        if (err && !mtd_is_bitflip(err)) {
                pr_err("Failed to read from %s at 0x%x\n", mtd->name, offset);
                goto err_put;
        }

        size = be32_to_cpu(hdr.size);

        buf = kmalloc(size + 1, GFP_KERNEL);
        if (!buf)
                goto err_put;

        err = mtd_read(mtd, offset + sizeof(hdr), size, &bytes_read, buf);
        if (err && !mtd_is_bitflip(err)) {
                pr_err("Failed to read from %s at 0x%zx\n", mtd->name, offset + sizeof(hdr));
                goto err_kfree;
        }

        buf[size] = '\0';

        of_node_put(np);

        return buf;

err_kfree:
        kfree(buf);
err_put:
        of_node_put(np);
        return NULL;
}

static int mtd_parser_tplink_safeloader_parse(struct mtd_info *mtd,
                                              const struct mtd_partition **pparts,
                                              struct mtd_part_parser_data *data)
{
        struct mtd_partition *parts;
        char name[65];
        size_t offset;
        size_t bytes;
        char *buf;
        int idx;
        int err;

        parts = kzalloc_objs(*parts, TPLINK_SAFELOADER_MAX_PARTS);
        if (!parts) {
                err = -ENOMEM;
                goto err_out;
        }

        buf = mtd_parser_tplink_safeloader_read_table(mtd);
        if (!buf) {
                err = -ENOENT;
                goto err_free_parts;
        }

        for (idx = 0, offset = TPLINK_SAFELOADER_DATA_OFFSET;
             idx < TPLINK_SAFELOADER_MAX_PARTS &&
             sscanf(buf + offset, "partition %64s base 0x%llx size 0x%llx%zn\n",
                    name, &parts[idx].offset, &parts[idx].size, &bytes) == 3;
             idx++, offset += bytes + 1) {
                parts[idx].name = kstrdup(name, GFP_KERNEL);
                if (!parts[idx].name) {
                        err = -ENOMEM;
                        goto err_free;
                }
        }

        if (idx == TPLINK_SAFELOADER_MAX_PARTS)
                pr_warn("Reached maximum number of partitions!\n");

        kfree(buf);

        *pparts = parts;

        return idx;

err_free:
        kfree(buf);
        for (idx -= 1; idx >= 0; idx--)
                kfree(parts[idx].name);
err_free_parts:
        kfree(parts);
err_out:
        return err;
};

static void mtd_parser_tplink_safeloader_cleanup(const struct mtd_partition *pparts,
                                                 int nr_parts)
{
        int i;

        for (i = 0; i < nr_parts; i++)
                kfree(pparts[i].name);

        kfree(pparts);
}

static const struct of_device_id mtd_parser_tplink_safeloader_of_match_table[] = {
        { .compatible = "tplink,safeloader-partitions" },
        {},
};
MODULE_DEVICE_TABLE(of, mtd_parser_tplink_safeloader_of_match_table);

static struct mtd_part_parser mtd_parser_tplink_safeloader = {
        .parse_fn = mtd_parser_tplink_safeloader_parse,
        .cleanup = mtd_parser_tplink_safeloader_cleanup,
        .name = "tplink-safeloader",
        .of_match_table = mtd_parser_tplink_safeloader_of_match_table,
};
module_mtd_part_parser(mtd_parser_tplink_safeloader);

MODULE_DESCRIPTION("TP-Link Safeloader partitions parser");
MODULE_LICENSE("GPL");