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/*
* MTD splitter for MikroTik NOR devices
*
* Copyright (C) 2017 Thibaut VARENE <varenet@parisc-linux.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.
*
* The rootfs is expected at erase-block boundary due to the use of
* mtd_find_rootfs_from(). We use a trimmed down version of the yaffs header
* for two main reasons:
* - the original header uses weakly defined types (int, enum...) which can
* vary in length depending on build host (and the struct is not packed),
* and the name field can have a different total length depending on
* whether or not the yaffs code was _built_ with unicode support.
* - the only field that could be of real use here (file_size_low) contains
* invalid data in the header generated by kernel2minor, so we cannot use
* it to infer the exact position of the rootfs and do away with
* mtd_find_rootfs_from() (and thus have non-EB-aligned rootfs).
*/
#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/string.h>
#include "mtdsplit.h"
#define YAFFS_OBJECT_TYPE_FILE 0x1
#define YAFFS_OBJECTID_ROOT 0x1
#define YAFFS_SUM_UNUSED 0xFFFF
#define YAFFS_NAME "kernel"
#define MINOR_NR_PARTS 2
/*
* This structure is based on yaffs_obj_hdr from yaffs_guts.h
* The weak types match upstream. The fields have cpu-endianness
*/
struct minor_header {
int yaffs_type;
int yaffs_obj_id;
u16 yaffs_sum_unused;
char yaffs_name[sizeof(YAFFS_NAME)];
};
static int mtdsplit_parse_minor(struct mtd_info *master,
const struct mtd_partition **pparts,
struct mtd_part_parser_data *data)
{
struct minor_header hdr;
size_t hdr_len, retlen;
size_t rootfs_offset;
struct mtd_partition *parts;
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;
/* match header */
if (hdr.yaffs_type != YAFFS_OBJECT_TYPE_FILE)
return -EINVAL;
if (hdr.yaffs_obj_id != YAFFS_OBJECTID_ROOT)
return -EINVAL;
if (hdr.yaffs_sum_unused != YAFFS_SUM_UNUSED)
return -EINVAL;
if (memcmp(hdr.yaffs_name, YAFFS_NAME, sizeof(YAFFS_NAME)))
return -EINVAL;
err = mtd_find_rootfs_from(master, master->erasesize, master->size,
&rootfs_offset, NULL);
if (err)
return err;
parts = kzalloc(MINOR_NR_PARTS * sizeof(*parts), GFP_KERNEL);
if (!parts)
return -ENOMEM;
parts[0].name = KERNEL_PART_NAME;
parts[0].offset = 0;
parts[0].size = rootfs_offset;
parts[1].name = ROOTFS_PART_NAME;
parts[1].offset = rootfs_offset;
parts[1].size = master->size - rootfs_offset;
*pparts = parts;
return MINOR_NR_PARTS;
}
static const struct of_device_id mtdsplit_minor_of_match_table[] = {
{ .compatible = "mikrotik,minor" },
{},
};
MODULE_DEVICE_TABLE(of, mtdsplit_minor_of_match_table);
static struct mtd_part_parser mtdsplit_minor_parser = {
.owner = THIS_MODULE,
.name = "minor-fw",
.of_match_table = mtdsplit_minor_of_match_table,
.parse_fn = mtdsplit_parse_minor,
.type = MTD_PARSER_TYPE_FIRMWARE,
};
static int __init mtdsplit_minor_init(void)
{
register_mtd_parser(&mtdsplit_minor_parser);
return 0;
}
subsys_initcall(mtdsplit_minor_init);
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