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| About | ||
| ===== | ||
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| 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). | ||
| 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: | ||
| - directory indexing - fast file find and list operations | ||
| - extents - fast big file truncate | ||
| - journaling transactions & recovery - power loss resistance | ||
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| Lwext4 may be used with SD/MMC card, USB flash drive or other block based memory device. However it is not good for flash memory–based storage devices. | ||
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| Code is also available on github: | ||
| https://github.com/gkostka/lwext4 | ||
| Lwext4 is an excellent choice for SD/MMC card, USB flash drive or other block based memory device. However it is not good for flash memory–based storage devices. | ||
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| Feel free to contact me: | ||
| [email protected] | ||
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| The most of the source code of lwext4 was taken from HelenOS: | ||
| * http://helenos.org/ | ||
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| Some features are based on FreeBSD and Linux implementations. | ||
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| KaHo Ng (https://github.com/ngkaho1234): | ||
| * advanced extents implementation | ||
| * xattr support | ||
| * metadata checksum support | ||
| * journal recovery | ||
| * journal recovery & transactions | ||
| * many bugfixes & improvements | ||
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| fuse-lwext4 project: | ||
| Lwext4 could be used also as fuse internals. Here is a nice project which uses lwext4 as a filesystem base: | ||
| * https://github.com/ngkaho1234/fuse-lwext4 | ||
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| Features | ||
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| * only C standard library dependency | ||
| * various CPU architectures supported (x86/64, cortex-mX, msp430 ...) | ||
| * small memory footprint | ||
| * flexible configurations | ||
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| Memory footprint (for cortex-m4) | ||
| Memory footprint | ||
| ------------ | ||
| * .text: 20KB - 40KB | ||
| * .data: 8KB (minimum 8 x 1KB block cache) | ||
| * .stack: 2KB | ||
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| 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: | ||
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| * .text: 20KB - only ext2 fs support , 50KB - full ext4 fs feature set | ||
| * .data: 8KB - minimum 8 x 1KB block cache, 12KB - when journaling and extents are enabled | ||
| * .stack: 2KB - is enough (not measured precisely) | ||
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| 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. | ||
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| Supported ext2/3/4 features | ||
| ===== | ||
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| ===== | ||
| * blockdev - block devices set, supported blockdev | ||
| * fs_test - test suite, mkfs and demo application | ||
| * lwext4 - internals of the lwext4 library | ||
| * toolchain - specific toolchain cmake files | ||
| * src - source files | ||
| * include - header files | ||
| * toolchain - cmake toolchain files | ||
| * CMakeLists.txt - CMake config file | ||
| * ext_images.7z - compressed ext2/3/4 100MB images | ||
| * fs_test.mk - automatic tests definitions | ||
| * Makefile - helper makefile to generate cmake and run test suite | ||
| * readme.mediawiki - readme file | ||
| * README.md - readme file | ||
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| Compile | ||
| ===== | ||
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| ===== | ||
| Toolchains needed: | ||
| ------------ | ||
| * arm-none-eabi-gcc for cortex-mX | ||
| * avr-gcc for avr | ||
| * bfin-elf-gcc for bfin | ||
| * msp430-gcc for msp430 | ||
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| Lwext4 could be compiled for many targets. Here are an examples for 8/16/32/64 bit architectures. | ||
| * generic for x86 or amd64 | ||
| * arm-none-eabi-gcc for ARM cortex-m0/m3/m4 microcontrollers | ||
| * avr-gcc for AVR xmega microcontrollers | ||
| * bfin-elf-gcc for blockfin processors | ||
| * msp430-gcc for msp430 microcontrollers | ||
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| 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. | ||
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| Build bf518 library: | ||
| ------------ | ||
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