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

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

#define BRCM_U_BOOT_MAX_OFFSET          0x200000
#define BRCM_U_BOOT_STEP                0x1000

#define BRCM_U_BOOT_MAX_PARTS           2

#define BRCM_U_BOOT_MAGIC               0x75456e76      /* uEnv */

struct brcm_u_boot_header {
        __le32 magic;
        __le32 length;
} __packed;

static const char *names[BRCM_U_BOOT_MAX_PARTS] = {
        "u-boot-env",
        "u-boot-env-backup",
};

static int brcm_u_boot_parse(struct mtd_info *mtd,
                             const struct mtd_partition **pparts,
                             struct mtd_part_parser_data *data)
{
        struct brcm_u_boot_header header;
        struct mtd_partition *parts;
        size_t bytes_read;
        size_t offset;
        int err;
        int i = 0;

        parts = kzalloc_objs(*parts, BRCM_U_BOOT_MAX_PARTS);
        if (!parts)
                return -ENOMEM;

        for (offset = 0;
             offset < min_t(size_t, mtd->size, BRCM_U_BOOT_MAX_OFFSET);
             offset += BRCM_U_BOOT_STEP) {
                err = mtd_read(mtd, offset, sizeof(header), &bytes_read, (uint8_t *)&header);
                if (err && !mtd_is_bitflip(err)) {
                        pr_err("Failed to read from %s at 0x%zx: %d\n", mtd->name, offset, err);
                        continue;
                }

                if (le32_to_cpu(header.magic) != BRCM_U_BOOT_MAGIC)
                        continue;

                parts[i].name = names[i];
                parts[i].offset = offset;
                parts[i].size = sizeof(header) + le32_to_cpu(header.length);
                i++;
                pr_info("offset:0x%zx magic:0x%08x BINGO\n", offset, header.magic);

                if (i == BRCM_U_BOOT_MAX_PARTS)
                        break;
        }

        *pparts = parts;

        return i;
};

static const struct of_device_id brcm_u_boot_of_match_table[] = {
        { .compatible = "brcm,u-boot" },
        {},
};
MODULE_DEVICE_TABLE(of, brcm_u_boot_of_match_table);

static struct mtd_part_parser brcm_u_boot_mtd_parser = {
        .parse_fn = brcm_u_boot_parse,
        .name = "brcm_u-boot",
        .of_match_table = brcm_u_boot_of_match_table,
};
module_mtd_part_parser(brcm_u_boot_mtd_parser);

MODULE_DESCRIPTION("Broadcom's U-Boot partition parser");
MODULE_LICENSE("GPL");