1UFFS: Ultra-low-cost Flash File System
2
3Project: http://uffs.sf.net/
4Blog: http://all-about-uffs.blogspot.com/
5Q/A: http://groups.google.com/group/uffs/
6
7Author: Ricky Zheng <[email protected]>
8
9INTRODUCTION
10------------
11
12UFFS is a nand flash file system designed for embedded system.
13
14UFFS have some unique and advanced features:
15 * Low cost: e.g. it needs only 41K bytes RAM for 64MB NAND flash (page size 2048).
16
17 * Fast booting: it reads only a few spares from each block, typically
18 mounting a fully filled file system (Gbits) within one second.
19
20 * Superb Reliability:
21 - The file system is designed for the embedded system which may
22 frequently lost power/reset without care.
23 - Journal file system, the file system will automatically rollback
24 to the last state when lost power on the middle of flash programing.
25 - When 'write' return without error, the data is guarenteed been
26 saved on flash.
27
28 * Fast file create/read/write/seek.
29 * Bad-block tolerant, ECC enable and good ware-leveling.
30 * There is no garbage collection needed for UFFS.
31 * Support multiple NAND flash class in one system.
32 * Support bare flash hardware, no operating system needed.
33 * Support static memory allocation (works without 'malloc').
34 * Fully simulated on PC (Windows/Linux) platform.
35
36Disadvantage:
37 * space inefficency for small files: UFFS use at least one
38 'block'(the minial erase unit for NAND flash, e.g. 16K ) for a file.
39 * maximum supported blocks: 2^16 = 65535
40
41Memory consuming example:
42 For page size = 512:
43 [VARY]Tree nodes: 16 * total_blocks
44 [CONST]Page Bufs: MAX_CACHED_BUFFERS(10) * (40 + pageSize(512)) = 5.4K
45 [CONST]Block Info caches: (24 + 14 * pages_per_block (32)) * MAX_CACHED_BLOCK_INFO (10) = 4.6K
46
47 Example 1: 128M bytes NAND, 8192 blocks, total memory cost:
48 (16 * 8192)128K + 5.4K + 4.6K = 138K bytes.
49
50 Example 2: 32M Bytes NAND, 2048 blocks, total memory cost:
51 (16 * 2048)32K + 5.4K + 4.6K = 42K bytes.
52
53 Example 3: 16M bytes NAND, 1024 blocks, total memory cost:
54 (16 * 1024)16K + 5.4K + 4.6K = 26K bytes.
55
56 For page size = 2048:
57 [VARY]Tree nodes: 16 * total_blocks
58 [CONST]Page Bufs: MAX_CACHED_BUFFERS(10) * (40 + pageSize(2048)) = 20.4K
59 [CONST]Block Info caches: (24 + 14 * pages_per_block (32)) * MAX_CACHED_BLOCK_INFO (10) = 4.6K
60
61 Example 1: 512M bytes NAND, 8192 blocks, total memory cost:
62 (16 * 8192)128K + 20.4K + 4.6K = 153K bytes.
63
64 Example 2: 128M Bytes NAND, 2048 blocks, total memory cost:
65 (16 * 2048)32K + 20.4K + 4.6K = 57K bytes.
66
67 Example 3: 64M bytes NAND, 1024 blocks, total memory cost:
68 (16 * 1024)16K + 20.4K + 4.6K = 41K bytes.
69
70
71BUILD SIMULATOR REQUIREMENT
72---------------------------
73From V1.2.0, build uffs simulator requires 'cmake'.
74'cmake' can be downloaded from: http://www.cmake.org/
75
76or, under Debian/Ubuntu:
77 sudo apt-get install cmake
78
79BUILD SIMULATOR ON LINUX
80------------------------
811) create a 'build' dir:
82
83mkdir -p ~/build/uffs
84
852) create Makefiles and build:
86 cd ~/build/uffs
87 cmake <path_to_uffs>
88 make
89
905) run simulator (interactive mode):
91 src/utils/mkuffs
92
93
94BUILD SIMULATOR ON WINDOWS
95--------------------------
96
971) create a 'build' dir along with uffs source dir,
98 d:\build\uffs
99
1002) Create VC project files:
101 cd build\uffs
102 cmake <path_to_uffs>
103
1043) Open uffs.dsw (or uffs.sln for VC > 6 ), compile & run.
105
106
107LATEST SOURCE CODE
108------------------
109You can get the latest source code from git repository:
110 git clone git://uffs.git.sourceforge.net/gitroot/uffs/uffs
111
112
113CURRENT STATUS
114--------------
115UFFS 0.1.x is a working version on PC simulator, also has been ported to
116uBase embedded OS as a 'real world' product for thousands of copies,
117it works fine so far.
118
119UFFS 0.2.0 implementes full directory.
120
121UFFS 1.0.0 is the first stable release at sf.net.
122
123UFFS 1.1.0: support NAND flash with large page size (up to 2K).
124
125UFFS 1.1.1: bug fixes. a tool for making uffs disk image.
126
127UFFS 1.1.2: bug fixes. add more Flash Class. change Licence from GNU GPLv2 to GNU LGPLv2
128
129UFFS 1.2.0:
130 - eliminate 'current path' and relatives. Now you should use absolute path in all
131 uffs APIs. For dir, the fullname should end with '/'.
132 - allow using static memory allocation, 'malloc' is no longer needed.
133 - using cmake for building simulator.
134 - bug fixes & minor changes.
135
136UFFS 1.2.1:
137 - improve bad block management
138 - bug fixes
139 - change Licence to modified GNU GPLv2.
140
141UFFS 1.3.0:
142 - improved flash interface
143 - support hardware ECC
144 - support user defined spare layout (for customized NAND flash controller)
145 - support 4K page size
146 - no partial page program required, support MLC NAND flash
147 - reduced buffer flushes by grouping buffers
148 - structual improvments and bug fixes
149
150UFFS v1.3.1:
151 - Tidy up three memory allocators: static, native and system.
152 - Fix bugs in flash interface example.
153 - Fix memory allocation bugs when using static memory allocator.
154 - Add flash driver interface 'WriteFullPage()'.
155 - Fix compilation errors for BlackFin DSP compiler.
156
157UFFS v1.3.2:
158 - Add POSIX like file system APIs.
159 - Bug fixes.
160
161UFFS v1.3.3:
162 - Change Flash Interface, simplify interface.
163 - Improved bad block handling.
164 - Better support for MLC NAND flash.
165 - Added hardware ECC and RS-ECC controller emulator.
166 - Bug fixes.
167
168UFFS v1.3.4
169 - New UO_NOECC option for skipping ECC (fast reading).
170 - POSIX compliance uffs_seek().
171 - Improved unclean page detection (add new 'seal' byte in spare area).
172 - Optional page data CRC.
173 - Bug fixes.
174 - Other improvements.
175
176LICENCE
177-------
178 From v1.2.1, UFFS is released under a modified GNU GPLv2. (the same as eCos Licence)
179 The full licence text can be found in the header of source files:
180
181 UFFS is free software; you can redistribute it and/or modify it under
182 the GNU Library General Public License as published by the Free Software
183 Foundation; either version 2 of the License, or (at your option) any
184 later version.
185
186 UFFS is distributed in the hope that it will be useful, but WITHOUT
187 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
188 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
189 or GNU Library General Public License, as applicable, for more details.
190
191 You should have received a copy of the GNU General Public License
192 and GNU Library General Public License along with UFFS; if not, write
193 to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
194 Boston, MA 02110-1301, USA.
195
196 As a special exception, if other files instantiate templates or use
197 macros or inline functions from this file, or you compile this file
198 and link it with other works to produce a work based on this file,
199 this file does not by itself cause the resulting work to be covered
200 by the GNU General Public License. However the source code for this
201 file must still be made available in accordance with section (3) of
202 the GNU General Public License v2.
203
204 This exception does not invalidate any other reasons why a work based
205 on this file might be covered by the GNU General Public License.
206
207
208TESTING UFFS WITH SQLITE3 REGRESSION TEST CASES
209-----------------------------------------------
210UFFS can be tested with sqlite3 regression test cases (on Linux).
211
2121) install tcl8.5-dev on host PC:
213 apt-get install tcl8.5 tcl8.5-dev
214
215 # make sure your Linux is using tcl8.5 as the default tclsh:
216 sudo update-alternatives --config tclsh
217 (select "tclsh8.5" from the list.)
218
2192) build uffs:
220 mkdir -p ~/build/uffs
221 cd ~/build/uffs
222 cmake <path_to_uffs>
223
2243) build sqlite3:
225 cd <path_to_uffs>/src/test/sqlite3/sqlite-src-3070900
226 ./configure # create some build support files
227 git checkout -f Makefile config.h # restore modified Makefile and config.h
228 make test # start build 'testfixture' program.
229
230 # now you'll see something like:
231 Connect: Connection refused
232 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
233 make: *** [test] Error 1
234
2354) run test cases:
236 Open two terminals.
237 on termional A:
238 cd ~/build/uffs
239 src/utils/mkuffs -t 1024
240
241 #on uffs simulator command line, enter:
242 format /
243 apisrv
244
245 on terminal B:
246 cd <path_to_uffs>/src/test/sqlite3/sqlite-src-3070900
247 ./test-uffs.sh
248
249 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.
250
251 The test will take 1~4 hours, depends on how fast your Linux box is.
252
253
254ACKNOWLEDGMENT
255---------------
256Special thanks for your contributions to:
257(list in no particular order)
258
259* Chen Jun <[email protected]>
260* Michail <[email protected]>
261* Sjpu <[email protected]>
262* RobertGray <[email protected]>
263* Dongbo <[email protected]>
264* Cag <[email protected]>
265* Sergey <[email protected]>
266* Chris Conrad <[email protected]>
267* Vladimir <[email protected]>
268* Thien Pham <[email protected]>
269* Emmanuel Blot <[email protected]>
270* Michael <[email protected]>
271* Mick D <[email protected]>
272* Paul <[email protected]>
273* Rogerz <[email protected]>
274
275
276