==About==



The main goal of the lwext4 project is to provide ext2/3/4 filesystem

library for microcontrolers with SD/MMC card support. Ext2/3/4, in my

opinion is one of the best filesystem for SD/MMC.



kostka.grzegorz@gmail.com



==Minimum memory requirements==



=====PROGRAM:=====

 - 20KB

=====RAM:=====

 - 8KB

=====STACK:=====

 - 2KB





==ext2/3/4 vs FAT32==

;ext2/3/4 > FAT32

* fseek operation on big file in FAT32 is IO heavy

* ext2/3/4 HTREE directories operations are faster than FAT32  

* ext4 extents makes truncate/remove opertion really fast

* more at https://ext4.wiki.kernel.org/index.php/Ext4_Disk_Layout



;ext2/3/4 < FAT32

* FAT32 has smaller footprint



==Credits==



A lot of the implementation of lwext4 was taken from HelenOS:

    http://helenos.org/

 

Some of ideas and features are based on FreeBSD and Linux implementations.



==Supported ext2/3/4 fs features==



;FEATURE_INCOMPAT (unable to mount with unsupported feature):

 COMPRESSION: no

 FILETYPE:    yes

 RECOVER:     no

 JOURNAL_DEV: no

 META_BG:     no

 EXTENTS:     yes

 64BIT:       yes

 MMP:         no

 FLEX_BG:     no

 EA_INODE:    no

 DIRDATA:     no

 

;FEATURE_COMPAT (able to mount with unsupported feature):

 DIR_PREALLOC:   no

 IMAGIC_INODES:  no

 HAS_JOURNAL:    no

 EXT_ATTR:       no

 RESIZE_INODE:   no

 DIR_INDEX:      yes



;FEATURE_RO (able to mount in read only mode):

 SPARSE_SUPER:  yes

 LARGE_FILE:    yes

 BTREE_DIR:     no

 HUGE_FILE:     yes

 GDT_CSUM:      yes

 DIR_NLINK:     yes

 EXTRA_ISIZE:   yes



==Supported filetypes:==

 FIFO:      no

 CHARDEV:   no

 DIRECTORY: yes

 BLOCKDEV:  no

 FILE:      yes

 SOFTLINK:  no

 SOCKET:    no



==Other==

 - block_size: 1KB, 2KB, 4KB ... 64KB

 - little/big endian architecture support





==Project tree==



 - blockdev         - block devices set, supported blockdevs

 -- filedev         - file based block device

 -- io_raw          - wiodows IO block device



 - demos            - demo directory sources

 -- generic         - generic demo app, used for development and and debbuging purpose

 

 - lwext4           - internals of the lwext4 library



 - toolchain        - specific toolchain cmake files



 - ext4.h           - lwext4 client library header

 - CMakeLists.txt   - CMake config file

 - ext_images.7z    - ext2/3/4 100MB images

 - Makefile         - helper makefile to call cmake

 - readme.mediawiki - yes, you are here ;)

  

==Compile: Windows==

;Tools needed:

* CMake:  http://www.cmake.org/cmake/resources/software.html

* MinGw:  http://www.mingw.org/

* GnuWin: http://gnuwin32.sourceforge.net/ 



;Create CMake files:

 make



;Remove CMake files:

 clean



;Build

 cd build_generic

 make



==Compile: Linux==



Tools needed:

 - CMake:  http://www.cmake.org/cmake/resources/software.html

 

;Create CMake files:

 make



;Remove CMake files:

 clean



;Build

 cd build_generic

 make



==Generic demo applicarion==



Features:

 - load ext2/3/4 images

 - load linux block device with ext2/3/4 part

 - load windows volume with ext2/3/4 filesystem 

 - directory speed test

 - file write/read speed test



How to use:

Windows/Linux fileimages:

 cd build_generic

 fileimage_demo --in ext2 



Windows volumes:

 cd build_generic

 fileimage_demo --in I: --wpart



Linux block devices:

 cd build_generic

 fileimage_demo --in /dev/your_block_device



Usage:                                                          

    --i   - input file              (default = ext2)            

    --rws - single R/W size         (default = 1024 * 1024)     

    --rwc - R/W count               (default = 10)                     

    --cache  - 0 static, 1 dynamic  (default = 1)               

    --dirs   - directory test count (default = 0)               

    --clean  - clean up after test                              

    --bstat  - block device stats                               

    --sbstat - superblock stats                                 

    --wpart  - windows partition mode                           





==Cross-Compile==



 Toolchain for ARM Cortex-m3/4: https://launchpad.net/gcc-arm-embedded

 Toolchain for Blackfin: http://blackfin.uclinux.org/doku.php



Build bf518 library:

 make bf518



Build cortex-m3 library:

 make cortex-m3



Build cortex-m4 library:

 make cortex-m4



==Ports==

 *Blackfin BF518 EZKIT SD Card Demo: TBD

 *STM32F4-Discovery SD Card Demo: TBD 



==Footprint==

                           

TBD