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yaffs2utils
-----------
The yaffs2utils is the collection of utilities to make/extract a YAFFS2/YAFFS1
image for Linux.

Currently, it inclueds the following tools:
(1) mkyaffs2: making a yaffs2 (yaffs1) image 
(2) unyaffs2: extract a yaffs2 (yaffs1) image made by mkyaffs2.
(3) unspare2: extract the spare(oob) layout from the NAND device.

This project is developed under the Debian Linux 5 (code Lenny). It can make a
yaffs2 image to be ran under my embedded system (Linux 2.6.20), and extract a
yaffs2 image made by itself. 

Due to some lack of the official utilities from yaffs2.net (A image made from
its "mkyaffs2image" tool cannot be ran normally under my embedded system because
of the wrong OOB origination), I re-wrote it almost and create the "mkyaffs2"
tool to make a yaffs2 image for Linux 2.6.20. A tool named "unyaffs2" is also
provided to extract the image made from its "mkyaffs2". The license for this 
package is stated as GPLv2 only.

Making a yaffs1 image to be ran properly is NOT verified, since I don't have an
embedded system device with the old NAND flash (512k page). I will be glad if
someone can help me to verify the integrity to make and extract a yaffs1 image.

* Project Page

	http://code.google.com/p/yaffs2utils/


HOWTO
-----
Building the source by "make", then enjoying them.


Usage
-----
* mkyaffs2

	./mkyaffs2 [-h] [-e] [-p pagesize] [-s sparesize] [-o oobimg] dirname imgfile

* unyaffs2

	./unyaffs2 [-h] [-e] [-p pagesize] [-s sparesize] [-o oobimg] [-f file] imgfile dirname

* unspare2

	./unspare2 [-h] [-e] devfile imgfile

After making a yaffs2 image, the tool "nandwrite" in the mtd-utils can be used
to recode data into the flash (with oob option), such as:

	nandwrite -a -o /dev/mtd${MTDNUM} ${YAFFS2IMAGE}

The option '-p' and '-s' can specify the page and spare size of the images, and
the information of the page and spare size should be available from your NAND
flash datasheet. If the oob layout is differed from the Linux default, the tool
"unspare2" can be used to extract the oob layout from the NAND device. If the
endian is different from your building system, The option "-e" is required while
executing the "unspare2" on the targets. Finally, by the option '-o' to specify
the oob image while using the "mkyaffs2/unyaffs2" can create/extract the YAFFS
image with the various oob layout for the different NAND devices.


Android
-------
Recently, I found that the most Android images are made from the official YAFFS2
tool - "mkyaffs2image". As the discussion in the previous section "yaffs2utils",
an image created by the official YAFFS2 tools (mkyaffs2image) can not be run on
the native Linux, because its oob layout is different from the default one in
the Linux MTD subsystem.

For an image is requested to be created/extracted with the compatibilities of
the one made by the official YFFS2 tool (mkyaffs2image), such as Android uses,
some methods are described:

1. Enable the CFLAGS in Makefile

   #CFLAGS	+= _HAVE_ANDROID


2. Modify the default the oob layout in the source by the following patch:

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
--- src.old/yaffs2utils_ecc.h	2011-06-20 16:23:45.000000000 +0800
+++ src.new/yaffs2utils_ecc.h	2011-06-20 16:22:55.000000000 +0800
@@ -32,7 +32,8 @@
         .eccpos = {40, 41, 42, 43, 44, 45, 46, 47,
                    48, 49, 50, 51, 52, 53, 54, 55,
                    56, 57, 58, 59, 60, 61, 62, 63},
-        .oobfree = {{.offset = 2, .length = 38}},
+//        .oobfree = {{.offset = 2, .length = 38}},
+        .oobfree = {{.offset = 0, .length = 38}},
 };
 
 static struct nand_ecclayout nand_oob_user = {0};
--------------------------------------------------------------------

3. Use "-o" option to specify the oob image, which can be available by using the
   tool "unspare2" on the target device, while creating/extracting the image.


LICENSE
-------
Except files under "src/yaffs2", yaffs2utils is published as GNU GPL version 2.
Files under "src/yaffs2" are branched from the official YAFFS2 and their license
are announced in their header.


TODO
----
1. Verify the implementation for yaffs1 images.
2. Extract the runtime image dumpped directly from the NAND flash.


NOTE
----
Files under "src/yaffs2" is branched from the official YAFFS2, because of the
compiling issues of the inconstant naming rules in the official YAFFS2 source.
These files are required by the current yaffs2utils. I will continue updating
these files untils the oficial source is integrated into the Linux kernel or it
has a stable release.


SPECIAL THANKS
--------------
1. Stijn Devriendt <[email protected]>


=============
Luen-Yung Lin
<[email protected]>