ref: 222d026d9875be802e35f75d07b127856bc214f4
parent: 2eb1882c69281f7a101aed4c62df1f707fea9a6e
author: gkostka <kostka.grzegorz@gmail.com>
date: Tue Feb 9 16:34:33 EST 2016
Update README.md
--- a/README.md
+++ b/README.md
@@ -5,13 +5,13 @@
About
=====
-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
-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.
+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.
-Code is also available on github:
-https://github.com/gkostka/lwext4
-
Feel free to contact me:
kostka.grzegorz@gmail.com
@@ -20,6 +20,7 @@
The most of the source code of lwext4 was taken from HelenOS:
* http://helenos.org/
+
Some features are based on FreeBSD and Linux implementations.
KaHo Ng (https://github.com/ngkaho1234):
@@ -26,10 +27,10 @@
* advanced extents implementation
* xattr support
* metadata checksum support
-* journal recovery
+* journal recovery & transactions
* many bugfixes & improvements
-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
Features
@@ -43,14 +44,23 @@
* only C standard library dependency
* various CPU architectures supported (x86/64, cortex-mX, msp430 ...)
* small memory footprint
+* flexible configurations
-
-Memory footprint (for cortex-m4)
+Memory footprint
------------
-* .text: 20KB - 40KB
-* .data: 8KB (minimum 8 x 1KB block cache)
-* .stack: 2KB
+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:
+
+* .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)
+
+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.
+
Supported ext2/3/4 features
=====
Features incompatible:
@@ -97,13 +107,14 @@
=====
* 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
Compile
=====
@@ -195,11 +206,18 @@
=====
Toolchains needed:
------------
-* arm-none-eabi-gcc for cortex-mX
-* avr-gcc for avr
-* bfin-elf-gcc for bfin
-* msp430-gcc for msp430
+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
+
+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.
Build bf518 library:
------------