yaffs2utils
===========

Overview
--------
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 6 (code Squeeze). 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. 

Because of the OOB scheme of a image made from the official yaffs2.net utilities
(mkyaffs2image) is defferend from the Linux MTD by default, a image made from
its "mkyaffs2image" tool cannot be ran normally under my native Linux system.
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|--help] [-e|--endian] [-p|--pagesize pagesize]
	           [-s|--sparesize sparesize] [-o|--oobimg oobimg]
	           [--all-root] [--yaffs-ecclayout] dirname imgfile

* unyaffs2

	./unyaffs2 [-h|--help] [-e|--endian] [-p|--pagesize pagesize]
	           [-s|--sparesize sparesize] [-o|--oobimg oobimg]
	           [-f|--fileset file] [--yaffs-ecclayout] imgfile dirname

* unspare2

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

mkyaffs2
--------
The tool "mkyaffs2" can create a YAFFS2 image 'imgfile' by files retrieved from
the directory 'dirname'. After a image is made, the tool "nandwrite" from the
mtd-utils can be used to write the raw data into the flash (with oob option),
such as:

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

Options '-p' and '-s' can specify the page and spare size of the images. The
information of the page and spare size should be obtained from your NAND
flash datasheet, or they would also be available by the "mtd_debug" tool in the
mtd-utils, such as:

	mtd_debug info /dev/mtd$(MTDNUM)

When the endian of a target system is different from your building machine, the
option '-e' has to be specified to convert the endian for your target system. 

The option '--all-root' could provide the capacity to make all files in the
target system are owned by root (UID = 0, GID = 0).

By default, the oob scheme used by native Linux is different from the one used
by the official "mkyaffs2image" tool. In Linux MTD subsystem, it use the first
two byte in the oob free area to mark the bad block, but the official tool
"mkyaffs2image" use all of the free area to record YAFFS2 private data (it has
its own bad block marker mechanism). If a image is requested to be created
compatibly with the one made from the official "mkyaffs2image" tool, the option
'--yaffs-ecclayout' has to be specified. It will create a image that use the
full free space in the oob area without shifting the first two byte for the bad
block marker by Linux MTD subsystem default.

unyaffs2
--------
The tool "unyaffs2" can extract the content of the image 'imgfile', which was
made by the 'mkyaffs2', into the directory "dirname".

As "mkyaffs2", it also provide the option '-p' and '-s' to specify the page and
spare size, and the option '-e' to provide the endian convert. When the image is
created by the tool using the YAFFS original oob scheme (such as the official
tool "mkyaffs2image", or the "mkyaffs2" with the option '--yaffs-ecclayout'),
the option '--yaffs-ecclayout' is also required.

When the option '-f' is applied, the "unyaffs2" can extract only the selection
of files from the YAFFS image, instead of the whole image content.

At this moment, the tool "unyaffs2" can only extract a image which is made from
the "mkyaffs2" exactly. Extractimg a image dumpped directly from the NAND device
is still unsupported (TODO list).

unspare2
--------
When the oob layout is different from the Linux defailt, the "unspare2" has the
capacity to dump the the oob scheme from the NAND device on the target into a 
file "imgfile", and the oob image file can be used by mkyaffs2/unyaffs2 with the
option "-o" to create/extract the suitable image. The endian convert option '-e'
is also provided while the endian of targets are different from the local
building system. 


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 (with the MTD subsystem), because its oob layout is different
from the default one in the Linux MTD subsystem.

As the discussion in the previous "Usage" section, for an image is requested to
be created/extracted with the compatibilities of the one made by the official
YFFS2 tool (mkyaffs2image), the option '--yaffs-ecclayout' of "mkyaffs2/unyaffs2"
has to be specified. With the option '--yaffs-ecclayout', the "mkyaffs2/unyaffs2"
will create/extract a image by using the YAFFS2 original oob scheme, instead of
using the Linux MTD oob layout by default.


COMPATIBILITY
=============

If a image is request to be created/extracted compatibly with the unknown oob
scheme which is different from the Linux, the tool "unspare" can be cross
compiled and used to extract the oob layout from the NAND flash on the target.
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.


LICENSE
=======

The package "yaffs2utils is published as GNU GPL version 2. Detalis about the
GNU GPL version 2 is shown in the file "COPYING".


TODO
====

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


NOTE
====

Files under "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]>