lwext4

==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