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Re: JFFS2 for NAND flash file system


On 31.05.2011 17:42, Ross Younger wrote:

> Running a non-NAND-aware filesystem on NAND is a very bad idea.

Is there any NAND-aware filesystem with eCos-compatible license?
I only know of jffs2 - yaffs2 is GPL or (a lot of) $$$ and ubifs
is also GPL.

Actually I am seeing this situation as a major drawback to eCos -
nowadays just about any device uses NAND for larger storage...

> Even reading a NAND page can, once in a while, cause a bit in-flash to
> flip (the "read disturb" effect). If your filesystem doesn't periodically
> refresh its contents, files and/or filesystem metadata which is frequently
> read but never changed will gradually rot.

Hmm, does jffs2 handle this? I don't remember seeing something like this
in the code, but maybe I did not look at recent enough one.

> Now, the public JFFS2 tree has had support for NAND flash since 2003.
> It looks like the version in eCos dates from around that time, though
> has its NAND support disabled; there's an argument to be made that this
> perhaps ought to be put right some time.

AFAIK when this was discussed there was some architectural problem -
Linux's jffs2 uses mtd layer and that code is GPL, so it needs
to be written from scratch:
http://www.cygwin.com/ml/ecos-discuss/2008-07/msg00055.html

-- 
                                           Stano

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