The main goal of the lwext4 project is to provide ext2/3/4 filesystem for microcontrollers. It may be an interesting alternative for traditional MCU filesystem libraries (mostly based on FAT32). Library has some cool and unique features in microcontrollers world:
Lwext4 is an excellent choice for SD/MMC card, USB flash drive or any other wear leveled memory types. However it is not good for raw flash devices.
Feel free to contact me: [email protected]
The most of the source code of lwext4 was taken from HelenOS:
Some features are based on FreeBSD and Linux implementations.
KaHo Ng (https://github.com/ngkaho1234):
Lwext4 could be used also as fuse internals. Here is a nice project which uses lwext4 as a filesystem base:
Some of the source files are licensed under GPLv2. It makes whole lwext4 GPLv2 licensed. To use library as a BSD3, GPLv2 licensed source files must be removed first. At this point there are two files licensed under GPLv2:
All other modules and headers are BSD-3-Clause licensed code.
Advanced ext4 filesystem features, like extents or journaling require some memory. However most of the memory expensive features could be disabled at compile time. Here is a brief summary for cortex-m4 processor:
Blocks are allocated dynamically. Previous versions of library could work without malloc but from 1.0.0 dynamic memory allocation is required. However, block cache should not allocate more than CONFIG_BLOCK_DEV CACHE_SIZE.
Download MSYS-2: https://sourceforge.net/projects/msys2/
Install required packages is MSYS2 Shell package manager:
pacman -S make gcc cmake p7zip
Package installation (Debian):
apt-get install make gcc cmake p7zip
make generic cd build_generic make sudo make install
Simple lwext4 library test application:
How to use for images/blockdevices:
lwext4-generic -i ext_images/ext2 lwext4-generic -i ext_images/ext3 lwext4-generic -i ext_images/ext4
Show full option set:
Execute tests for 100MB unpacked images:
Execute tests for autogenerated 1GB images (only on Linux targets) + fsck:
It is possible to create ext2/3/4 partition by internal library tool.
Generate empty file (1GB):
dd if=/dev/zero of=ext_image bs=1M count=1024
Create ext2 partition:
lwext4-mkfs -i ext_image -e 2
Create ext3 partition:
lwext4-mkfs -i ext_image -e 3
Create ext4 partition:
lwext4-mkfs -i ext_image -e 4
Show full option set:
Lwext4 could be compiled for many targets. Here are an examples for 8/16/32/64 bit architectures.
Library has been tested only for generic (amd64) & ARM Cortex M architectures. For other targets compilation passes (with warnings somewhere) but tests are not done yet. Lwext4 code is written with endianes respect. Big endian behavior also hasn't been tested yet.
make avrxmega7 cd build_avrxmega7 make lwext4
make cortex-m0 cd build_cortex-m0 make lwext4
make cortex-m3 cd build_cortex-m3 make lwext4
make cortex-m4 cd build_cortex-m4 make lwext4