OpenWrt – Rev 3

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/*
 *  Copyright (C) 2013 Gabor Juhos <juhosg@openwrt.org>
 *
 *  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.
 *
 */

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

#include "mtdsplit.h"

#define SEAMA_MAGIC             0x5EA3A417
#define SEAMA_NR_PARTS          2
#define SEAMA_MIN_ROOTFS_OFFS   0x80000 /* 512KiB */

struct seama_header {
        __be32  magic;          /* should always be SEAMA_MAGIC. */
        __be16  reserved;       /* reserved for  */
        __be16  metasize;       /* size of the META data */
        __be32  size;           /* size of the image */
        u8      md5[16];        /* digest */
};

static int mtdsplit_parse_seama(struct mtd_info *master,
                                const struct mtd_partition **pparts,
                                struct mtd_part_parser_data *data)
{
        struct seama_header hdr;
        size_t hdr_len, retlen, kernel_ent_size;
        size_t rootfs_offset;
        struct mtd_partition *parts;
        enum mtdsplit_part_type type;
        int err;

        hdr_len = sizeof(hdr);
        err = mtd_read(master, 0, hdr_len, &retlen, (void *) &hdr);
        if (err)
                return err;

        if (retlen != hdr_len)
                return -EIO;

        /* sanity checks */
        if (be32_to_cpu(hdr.magic) != SEAMA_MAGIC)
                return -EINVAL;

        kernel_ent_size = hdr_len + be32_to_cpu(hdr.size) +
                          be16_to_cpu(hdr.metasize);
        if (kernel_ent_size > master->size)
                return -EINVAL;

        /* Check for the rootfs right after Seama entity with a kernel. */
        err = mtd_check_rootfs_magic(master, kernel_ent_size, &type);
        if (!err) {
                rootfs_offset = kernel_ent_size;
        } else {
                /*
                 * On some devices firmware entity might contain both: kernel
                 * and rootfs. We can't determine kernel size so we just have to
                 * look for rootfs magic.
                 * Start the search from an arbitrary offset.
                 */
                err = mtd_find_rootfs_from(master, SEAMA_MIN_ROOTFS_OFFS,
                                           master->size, &rootfs_offset, &type);
                if (err)
                        return err;
        }

        parts = kzalloc(SEAMA_NR_PARTS * sizeof(*parts), GFP_KERNEL);
        if (!parts)
                return -ENOMEM;

        parts[0].name = KERNEL_PART_NAME;
        parts[0].offset = sizeof hdr + be16_to_cpu(hdr.metasize);
        parts[0].size = rootfs_offset - parts[0].offset;

        if (type == MTDSPLIT_PART_TYPE_UBI)
                parts[1].name = UBI_PART_NAME;
        else
                parts[1].name = ROOTFS_PART_NAME;
        parts[1].offset = rootfs_offset;
        parts[1].size = master->size - rootfs_offset;

        *pparts = parts;
        return SEAMA_NR_PARTS;
}

static struct mtd_part_parser mtdsplit_seama_parser = {
        .owner = THIS_MODULE,
        .name = "seama-fw",
        .parse_fn = mtdsplit_parse_seama,
        .type = MTD_PARSER_TYPE_FIRMWARE,
};

static int __init mtdsplit_seama_init(void)
{
        register_mtd_parser(&mtdsplit_seama_parser);

        return 0;
}

subsys_initcall(mtdsplit_seama_init);