LXR busybox/util-linux/volume

   1/*
   2 * volume_id - reads filesystem label and uuid
   3 *
   4 * Copyright (C) 2018 Sven-Göran Bergh <sgb@systemaxion.se>
   5 *
   6 * Licensed under GPLv2, see file LICENSE in this source tree.
   7 */
   8//config:config FEATURE_VOLUMEID_LFS
   9//config:       bool "LittleFS filesystem"
  10//config:       default y
  11//config:       depends on VOLUMEID && FEATURE_BLKID_TYPE
  12//config:       help
  13//config:       LittleFS is a small fail-safe filesystem designed for embedded
  14//config:       systems. It has strong copy-on-write guarantees and storage on disk
  15//config:       is always kept in a valid state. It also provides a form of dynamic
  16//config:       wear levelling for systems that can not fit a full flash translation
  17//config:       layer.
  18
  19//kbuild:lib-$(CONFIG_FEATURE_VOLUMEID_LFS) += lfs.o
  20
  21#include "volume_id_internal.h"
  22
  23#define LFS_SB1_OFFSET          0x10
  24#define LFS_MAGIC_NAME          "littlefs"
  25#define LFS_MAGIC_LEN           8
  26
  27// The superblock is stored in the first metadata pair, i.e the first two blocks.
  28struct lfs_super_block {        // A block in a metadata pair
  29// /* 0x00 */   uint32_t        rev_count;              // Revision count
  30// /* 0x04 */   uint32_t        dir_size;               // Directory size
  31// /* 0x08 */   uint64_t        tail_ptr;               // Tail pointer
  32/* 0x10 */      uint8_t         entry_type;             // Entry type
  33/* 0x11 */      uint8_t         entry_len;              // Entry length
  34/* 0x12 */      uint8_t         att_len;                // Attribute length
  35/* 0x13 */      uint8_t         name_len;               // Name length
  36/* 0x14 */      uint64_t        root_dir;               // Root directory
  37/* 0x1C */      uint32_t        block_size;             // Block size
  38/* 0x20 */      uint32_t        block_count;            // Block count
  39/* 0x24 */      uint16_t        ver_major;              // Version major
  40/* 0x26 */      uint16_t        ver_minor;              // Version minor
  41/* 0x28 */      uint8_t         magic[LFS_MAGIC_LEN];   // Magic string "littlefs"
  42// /* 0x30 */   uint32_t        crc;                    // CRC-32 checksum
  43} PACKED;
  44
  45int FAST_FUNC volume_id_probe_lfs(struct volume_id *id /*,uint64_t off*/)
  46{
  47        struct lfs_super_block *sb;
  48
  49        // Go for primary super block (ignore second sb)
  50        dbg("lfs: probing at offset 0x%x", LFS_SB1_OFFSET);
  51        sb = volume_id_get_buffer(id, LFS_SB1_OFFSET, sizeof(*sb));
  52
  53        if (!sb)
  54                return -1;
  55
  56        if (memcmp(sb->magic, LFS_MAGIC_NAME, LFS_MAGIC_LEN) != 0)
  57                return -1;
  58
  59        IF_FEATURE_BLKID_TYPE(id->type = LFS_MAGIC_NAME);
  60
  61        return 0;
  62}
  63