2 * MTD splitter for MikroTik NOR devices
4 * Copyright (C) 2017 Thibaut VARENE <varenet@parisc-linux.org>
6 * This program is free software; you can redistribute it and/or modify it
7 * under the terms of the GNU General Public License version 2 as published
8 * by the Free Software Foundation.
10 * The rootfs is expected at erase-block boundary due to the use of
11 * mtd_find_rootfs_from(). We use a trimmed down version of the yaffs header
12 * for two main reasons:
13 * - the original header uses weakly defined types (int, enum...) which can
14 * vary in length depending on build host (and the struct is not packed),
15 * and the name field can have a different total length depending on
16 * whether or not the yaffs code was _built_ with unicode support.
17 * - the only field that could be of real use here (file_size_low) contains
18 * invalid data in the header generated by kernel2minor, so we cannot use
19 * it to infer the exact position of the rootfs and do away with
20 * mtd_find_rootfs_from() (and thus have non-EB-aligned rootfs).
23 #include <linux/module.h>
24 #include <linux/init.h>
25 #include <linux/kernel.h>
26 #include <linux/slab.h>
27 #include <linux/mtd/mtd.h>
28 #include <linux/mtd/partitions.h>
29 #include <linux/string.h>
33 #define YAFFS_OBJECT_TYPE_FILE 0x1
34 #define YAFFS_OBJECTID_ROOT 0x1
35 #define YAFFS_SUM_UNUSED 0xFFFF
36 #define YAFFS_NAME "kernel"
38 #define MINOR_NR_PARTS 2
41 * This structure is based on yaffs_obj_hdr from yaffs_guts.h
42 * The weak types match upstream. The fields have cpu-endianness
48 char yaffs_name[sizeof(YAFFS_NAME)];
51 static int mtdsplit_parse_minor(struct mtd_info *master,
52 const struct mtd_partition **pparts,
53 struct mtd_part_parser_data *data)
55 struct minor_header hdr;
56 size_t hdr_len, retlen;
58 struct mtd_partition *parts;
61 hdr_len = sizeof(hdr);
62 err = mtd_read(master, 0, hdr_len, &retlen, (void *) &hdr);
66 if (retlen != hdr_len)
70 if (hdr.yaffs_type != YAFFS_OBJECT_TYPE_FILE)
73 if (hdr.yaffs_obj_id != YAFFS_OBJECTID_ROOT)
76 if (hdr.yaffs_sum_unused != YAFFS_SUM_UNUSED)
79 if (memcmp(hdr.yaffs_name, YAFFS_NAME, sizeof(YAFFS_NAME)))
82 err = mtd_find_rootfs_from(master, master->erasesize, master->size,
83 &rootfs_offset, NULL);
87 parts = kzalloc(MINOR_NR_PARTS * sizeof(*parts), GFP_KERNEL);
91 parts[0].name = KERNEL_PART_NAME;
93 parts[0].size = rootfs_offset;
95 parts[1].name = ROOTFS_PART_NAME;
96 parts[1].offset = rootfs_offset;
97 parts[1].size = master->size - rootfs_offset;
100 return MINOR_NR_PARTS;
103 static struct mtd_part_parser mtdsplit_minor_parser = {
104 .owner = THIS_MODULE,
106 .parse_fn = mtdsplit_parse_minor,
107 .type = MTD_PARSER_TYPE_FIRMWARE,
110 static int __init mtdsplit_minor_init(void)
112 register_mtd_parser(&mtdsplit_minor_parser);
117 subsys_initcall(mtdsplit_minor_init);