276 lines
9.5 KiB
Plaintext
276 lines
9.5 KiB
Plaintext
UFFS: Ultra-low-cost Flash File System
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Project: http://uffs.sf.net/
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Blog: http://all-about-uffs.blogspot.com/
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Q/A: http://groups.google.com/group/uffs/
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Author: Ricky Zheng <ricky_gz_zheng@yahoo.co.nz>
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INTRODUCTION
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------------
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UFFS is a nand flash file system designed for embedded system.
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UFFS have some unique and advanced features:
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* Low cost: e.g. it needs only 41K bytes RAM for 64MB NAND flash (page size 2048).
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* Fast booting: it reads only a few spares from each block, typically
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mounting a fully filled file system (Gbits) within one second.
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* Superb Reliability:
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- The file system is designed for the embedded system which may
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frequently lost power/reset without care.
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- Journal file system, the file system will automatically rollback
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to the last state when lost power on the middle of flash programing.
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- When 'write' return without error, the data is guarenteed been
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saved on flash.
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* Fast file create/read/write/seek.
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* Bad-block tolerant, ECC enable and good ware-leveling.
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* There is no garbage collection needed for UFFS.
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* Support multiple NAND flash class in one system.
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* Support bare flash hardware, no operating system needed.
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* Support static memory allocation (works without 'malloc').
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* Fully simulated on PC (Windows/Linux) platform.
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Disadvantage:
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* space inefficency for small files: UFFS use at least one
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'block'(the minial erase unit for NAND flash, e.g. 16K ) for a file.
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* maximum supported blocks: 2^16 = 65535
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Memory consuming example:
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For page size = 512:
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[VARY]Tree nodes: 16 * total_blocks
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[CONST]Page Bufs: MAX_CACHED_BUFFERS(10) * (40 + pageSize(512)) = 5.4K
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[CONST]Block Info caches: (24 + 14 * pages_per_block (32)) * MAX_CACHED_BLOCK_INFO (10) = 4.6K
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Example 1: 128M bytes NAND, 8192 blocks, total memory cost:
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(16 * 8192)128K + 5.4K + 4.6K = 138K bytes.
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Example 2: 32M Bytes NAND, 2048 blocks, total memory cost:
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(16 * 2048)32K + 5.4K + 4.6K = 42K bytes.
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Example 3: 16M bytes NAND, 1024 blocks, total memory cost:
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(16 * 1024)16K + 5.4K + 4.6K = 26K bytes.
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For page size = 2048:
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[VARY]Tree nodes: 16 * total_blocks
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[CONST]Page Bufs: MAX_CACHED_BUFFERS(10) * (40 + pageSize(2048)) = 20.4K
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[CONST]Block Info caches: (24 + 14 * pages_per_block (32)) * MAX_CACHED_BLOCK_INFO (10) = 4.6K
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Example 1: 512M bytes NAND, 8192 blocks, total memory cost:
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(16 * 8192)128K + 20.4K + 4.6K = 153K bytes.
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Example 2: 128M Bytes NAND, 2048 blocks, total memory cost:
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(16 * 2048)32K + 20.4K + 4.6K = 57K bytes.
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Example 3: 64M bytes NAND, 1024 blocks, total memory cost:
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(16 * 1024)16K + 20.4K + 4.6K = 41K bytes.
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BUILD SIMULATOR REQUIREMENT
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---------------------------
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From V1.2.0, build uffs simulator requires 'cmake'.
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'cmake' can be downloaded from: http://www.cmake.org/
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or, under Debian/Ubuntu:
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sudo apt-get install cmake
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BUILD SIMULATOR ON LINUX
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------------------------
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1) create a 'build' dir:
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mkdir -p ~/build/uffs
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2) create Makefiles and build:
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cd ~/build/uffs
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cmake <path_to_uffs>
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make
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5) run simulator (interactive mode):
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src/utils/mkuffs
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BUILD SIMULATOR ON WINDOWS
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--------------------------
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1) create a 'build' dir along with uffs source dir,
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d:\build\uffs
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2) Create VC project files:
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cd build\uffs
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cmake <path_to_uffs>
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3) Open uffs.dsw (or uffs.sln for VC > 6 ), compile & run.
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LATEST SOURCE CODE
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------------------
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You can get the latest source code from git repository:
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git clone git://uffs.git.sourceforge.net/gitroot/uffs/uffs
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CURRENT STATUS
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--------------
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UFFS 0.1.x is a working version on PC simulator, also has been ported to
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uBase embedded OS as a 'real world' product for thousands of copies,
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it works fine so far.
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UFFS 0.2.0 implementes full directory.
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UFFS 1.0.0 is the first stable release at sf.net.
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UFFS 1.1.0: support NAND flash with large page size (up to 2K).
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UFFS 1.1.1: bug fixes. a tool for making uffs disk image.
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UFFS 1.1.2: bug fixes. add more Flash Class. change Licence from GNU GPLv2 to GNU LGPLv2
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UFFS 1.2.0:
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- eliminate 'current path' and relatives. Now you should use absolute path in all
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uffs APIs. For dir, the fullname should end with '/'.
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- allow using static memory allocation, 'malloc' is no longer needed.
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- using cmake for building simulator.
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- bug fixes & minor changes.
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UFFS 1.2.1:
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- improve bad block management
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- bug fixes
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- change Licence to modified GNU GPLv2.
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UFFS 1.3.0:
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- improved flash interface
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- support hardware ECC
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- support user defined spare layout (for customized NAND flash controller)
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- support 4K page size
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- no partial page program required, support MLC NAND flash
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- reduced buffer flushes by grouping buffers
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- structual improvments and bug fixes
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UFFS v1.3.1:
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- Tidy up three memory allocators: static, native and system.
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- Fix bugs in flash interface example.
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- Fix memory allocation bugs when using static memory allocator.
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- Add flash driver interface 'WriteFullPage()'.
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- Fix compilation errors for BlackFin DSP compiler.
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UFFS v1.3.2:
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- Add POSIX like file system APIs.
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- Bug fixes.
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UFFS v1.3.3:
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- Change Flash Interface, simplify interface.
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- Improved bad block handling.
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- Better support for MLC NAND flash.
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- Added hardware ECC and RS-ECC controller emulator.
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- Bug fixes.
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UFFS v1.3.4
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- New UO_NOECC option for skipping ECC (fast reading).
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- POSIX compliance uffs_seek().
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- Improved unclean page detection (add new 'seal' byte in spare area).
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- Optional page data CRC.
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- Bug fixes.
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- Other improvements.
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LICENCE
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-------
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From v1.2.1, UFFS is released under a modified GNU GPLv2. (the same as eCos Licence)
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The full licence text can be found in the header of source files:
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UFFS is free software; you can redistribute it and/or modify it under
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the GNU Library General Public License as published by the Free Software
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Foundation; either version 2 of the License, or (at your option) any
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later version.
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UFFS is distributed in the hope that it will be useful, but WITHOUT
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ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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or GNU Library General Public License, as applicable, for more details.
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You should have received a copy of the GNU General Public License
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and GNU Library General Public License along with UFFS; if not, write
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to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
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Boston, MA 02110-1301, USA.
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As a special exception, if other files instantiate templates or use
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macros or inline functions from this file, or you compile this file
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and link it with other works to produce a work based on this file,
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this file does not by itself cause the resulting work to be covered
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by the GNU General Public License. However the source code for this
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file must still be made available in accordance with section (3) of
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the GNU General Public License v2.
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This exception does not invalidate any other reasons why a work based
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on this file might be covered by the GNU General Public License.
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TESTING UFFS WITH SQLITE3 REGRESSION TEST CASES
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-----------------------------------------------
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UFFS can be tested with sqlite3 regression test cases (on Linux).
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1) install tcl8.5-dev on host PC:
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apt-get install tcl8.5 tcl8.5-dev
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# make sure your Linux is using tcl8.5 as the default tclsh:
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sudo update-alternatives --config tclsh
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(select "tclsh8.5" from the list.)
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2) build uffs:
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mkdir -p ~/build/uffs
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cd ~/build/uffs
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cmake <path_to_uffs>
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3) build sqlite3:
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cd <path_to_uffs>/src/test/sqlite3/sqlite-src-3070900
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./configure # create some build support files
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git checkout -f Makefile config.h # restore modified Makefile and config.h
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make test # start build 'testfixture' program.
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# now you'll see something like:
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Connect: Connection refused
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Assert (uffs_ret == ret && ret == bak_ret) fail at /home/.../src/test/api_test/os_uffs.c:os_unlink:329: unlink("/home/.../src/test/sqlite3/sqlite-src-3070900/./test.db-journal"), unix return 0, uffs return -1, bak return -1
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make: *** [test] Error 1
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4) run test cases:
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Open two terminals.
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on termional A:
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cd ~/build/uffs
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src/utils/mkuffs -t 1024
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#on uffs simulator command line, enter:
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format /
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apisrv
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on terminal B:
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cd <path_to_uffs>/src/test/sqlite3/sqlite-src-3070900
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./test-uffs.sh
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Note: if you want to run mkuffs on another PC, for example, a Windows PC, you need to specify the IP address in test-uffs.sh.
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The test will take 1~4 hours, depends on how fast your Linux box is.
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ACKNOWLEDGMENT
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---------------
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Special thanks for your contributions to:
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(list in no particular order)
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* Chen Jun <chj@nlscan.com>
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* Michail <digiolog@mail.ru>
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* Sjpu <sjpu@163.com>
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* RobertGray <xennex@hotmail.com>
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* Dongbo <dongbo@ftsafe.com>
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* Cag <seucag@hotmail.com>
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* Sergey <s_sazonov@m2m-t.ru>
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* Chris Conrad <chris.conrad@halliburton.com>
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* Vladimir <decoder@rambler.ru>
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* Thien Pham <thienpham2008@yahoo.com>
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* Emmanuel Blot <eblot.ml@gmail.com>
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* Michael <yowong2@gmail.com>
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* Mick D <mick-eng@sourceforge.net>
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* Paul <paulr227@gmail.com>
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* Rogerz <rogerz.zhang@gmail.com>
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