fs/jffs2/Kconfig v3.0-rc7


Journalling Flash File System v2 (JFFS2) support

JFFS2 is the second generation of the Journalling Flash File System
for use on diskless embedded devices. It provides improved wear
levelling, compression and support for hard links. You cannot use
this on normal block devices, only on 'MTD' devices.

Further information on the design and implementation of JFFS2 is
available at <http://sources.redhat.com/jffs2/>.


JFFS2 debugging verbosity (0 = quiet, 2 = noisy)

This controls the amount of debugging messages produced by the JFFS2
code. Set it to zero for use in production systems. For evaluation,
testing and debugging, it's advisable to set it to one. This will
enable a few assertions and will print debugging messages at the
KERN_DEBUG loglevel, where they won't normally be visible. Level 2
is unlikely to be useful - it enables extra debugging in certain
areas which at one point needed debugging, but when the bugs were
located and fixed, the detailed messages were relegated to level 2.

If reporting bugs, please try to have available a full dump of the
messages at debug level 1 while the misbehaviour was occurring.


JFFS2 write-buffering support

This enables the write-buffering support in JFFS2.

This functionality is required to support JFFS2 on the following
types of flash devices:
- NAND flash
- NOR flash with transparent ECC
- DataFlash


Verify JFFS2 write-buffer reads

This causes JFFS2 to read back every page written through the
write-buffer, and check for errors.


JFFS2 summary support (EXPERIMENTAL)

This feature makes it possible to use summary information
for faster filesystem mount.

The summary information can be inserted into a filesystem image
by the utility 'sumtool'.

If unsure, say 'N'.



Extended attributes are name:value pairs associated with inodes by
the kernel or by users (see the attr(5) manual page, or visit
<http://acl.bestbits.at/> for details).

If unsure, say N.


JFFS2 POSIX Access Control Lists

Posix Access Control Lists (ACLs) support permissions for users and
groups beyond the owner/group/world scheme.

To learn more about Access Control Lists, visit the Posix ACLs for
Linux website <http://acl.bestbits.at/>.

If you don't know what Access Control Lists are, say N


JFFS2 Security Labels

Security labels support alternative access control models
implemented by security modules like SELinux.  This option
enables an extended attribute handler for file security
labels in the jffs2 filesystem.

If you are not using a security module that requires using
extended attributes for file security labels, say N.


Advanced compression options for JFFS2

Enabling this option allows you to explicitly choose which
compression modules, if any, are enabled in JFFS2. Removing
compressors can mean you cannot read existing file systems,
and enabling experimental compressors can mean that you
write a file system which cannot be read by a standard kernel.

If unsure, you should _definitely_ say 'N'.


JFFS2 ZLIB compression support

Zlib is designed to be a free, general-purpose, legally unencumbered,
lossless data-compression library for use on virtually any computer
hardware and operating system. See <http://www.gzip.org/zlib/> for
further information.

Say 'Y' if unsure.


JFFS2 LZO compression support

minilzo-based compression. Generally works better than Zlib.

This feature was added in July, 2007. Say 'N' if you need
compatibility with older bootloaders or kernels.


JFFS2 RTIME compression support

Rtime does manage to recompress already-compressed data. Say 'Y' if unsure.


JFFS2 RUBIN compression support

RUBINMIPS and DYNRUBIN compressors. Say 'N' if unsure.


JFFS2 default compression mode

You can set here the default compression mode of JFFS2 from
the available compression modes. Don't touch if unsure.


no compression

Uses no compression.



Tries the compressors in a predefined order and chooses the first
successful one.



Tries all compressors and chooses the one which has the smallest


Favour LZO

Tries all compressors and chooses the one which has the smallest
result but gives some preference to LZO (which has faster
decompression) at the expense of size.