fatfsgen.py: enabled automatic detection of the FATFS type for FAT12 and FAT16

2025-08-11 13:00:19 +00:00 · 2021-12-06 18:17:20 +01:00
parent 6ddf2ea05e
commit f3425dea96
13 changed files with 390 additions and 119 deletions
--- a/components/fatfs/fatfsgen_utils/fatfs_parser.py
+++ b/components/fatfs/fatfsgen_utils/fatfs_parser.py
@@ -0,0 +1,67 @@
+# SPDX-FileCopyrightText: 2021-2022 Espressif Systems (Shanghai) CO LTD
+# SPDX-License-Identifier: Apache-2.0
+from construct import Const, Int8ul, Int16ul, Int32ul, PaddedString, Struct
+
+from .utils import (BYTES_PER_DIRECTORY_ENTRY, get_fatfs_type, get_non_data_sectors_cnt, number_of_clusters,
+                    read_filesystem)
+
+
+class FATFSParser:
+    MAX_VOL_LAB_SIZE = 11
+    MAX_OEM_NAME_SIZE = 8
+    MAX_FS_TYPE_SIZE = 8
+
+    # the FAT specification defines 512 bytes for the boot sector header
+    BOOT_HEADER_SIZE = 512
+
+    BOOT_SECTOR_HEADER = Struct(
+        'BS_jmpBoot' / Const(b'\xeb\xfe\x90'),
+        'BS_OEMName' / PaddedString(MAX_OEM_NAME_SIZE, 'utf-8'),
+        'BPB_BytsPerSec' / Int16ul,
+        'BPB_SecPerClus' / Int8ul,
+        'BPB_RsvdSecCnt' / Int16ul,
+        'BPB_NumFATs' / Int8ul,
+        'BPB_RootEntCnt' / Int16ul,
+        'BPB_TotSec16' / Int16ul,
+        'BPB_Media' / Int8ul,
+        'BPB_FATSz16' / Int16ul,
+        'BPB_SecPerTrk' / Int16ul,
+        'BPB_NumHeads' / Int16ul,
+        'BPB_HiddSec' / Int32ul,
+        'BPB_TotSec32' / Int32ul,
+        'BS_DrvNum' / Const(b'\x80'),
+        'BS_Reserved1' / Const(b'\x00'),
+        'BS_BootSig' / Const(b'\x29'),
+        'BS_VolID' / Int32ul,
+        'BS_VolLab' / PaddedString(MAX_VOL_LAB_SIZE, 'utf-8'),
+        'BS_FilSysType' / PaddedString(MAX_FS_TYPE_SIZE, 'utf-8'),
+        'BS_EMPTY' / Const(448 * b'\x00'),
+        'Signature_word' / Const(b'\x55\xAA')
+    )
+    assert BOOT_SECTOR_HEADER.sizeof() == BOOT_HEADER_SIZE
+
+    def __init__(self, image_file_path: str, wl_support: bool = False) -> None:
+        if wl_support:
+            raise NotImplementedError('Parser is not implemented for WL yet.')
+        self.fatfs = read_filesystem(image_file_path)
+
+        # when wl is not supported we expect boot sector to be the first
+        self.parsed_header = FATFSParser.BOOT_SECTOR_HEADER.parse(self.fatfs[:FATFSParser.BOOT_HEADER_SIZE])
+
+    def print(self) -> None:
+        print('Properties of the FATFS:')
+        for key in self.parsed_header.keys():
+            if key in ('_io', 'BS_EMPTY', 'Signature_word'):
+                continue
+            print('  {}: {}'.format(key.replace('BPB_', '').replace('BS_', ''), self.parsed_header[key]))
+        root_dir_cnt = (self.parsed_header['BPB_RootEntCnt'] * BYTES_PER_DIRECTORY_ENTRY) // self.parsed_header[
+            'BPB_BytsPerSec']
+        non_data_sectors = get_non_data_sectors_cnt(self.parsed_header['BPB_RsvdSecCnt'],
+                                                    # this has to be changed when FAT32 is supported
+                                                    self.parsed_header['BPB_FATSz16'], root_dir_cnt)
+        data_clusters = self.parsed_header['BPB_TotSec16'] - non_data_sectors
+        clusters_num = number_of_clusters(data_clusters, self.parsed_header['BPB_SecPerClus'])
+        assert self.parsed_header['BPB_BytsPerSec'] in (512, 1024, 2048, 4096)
+        assert self.parsed_header['BPB_SecPerClus'] in (1, 2, 4, 8, 16, 32, 64, 128)
+        print(f'  Clusters number: {clusters_num}')
+        print(f'  FATFS type: FAT{get_fatfs_type(clusters_num)}')