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Re: FAT32 over NAND


Andrew Lunn wrote:
On Tue, Jan 20, 2009 at 07:38:02PM +0530, Himanshu Patel wrote:
Hi,

We want to have FAT32 file system over NAND flash. Is it possible? What
approach should we take for developing the same?

If you look back in the archive, last year there was some work to get YAFFS on NAND working. I would suggest trying to build on the NAND infrastructure that provided.

I implemented basic NAND flash functionality and a wrapper layer for YAFFS2, a file system designed specifically for NAND flash. For an alpha release (and maybe later on, beta release) of my code, see: http://www.cs.vu.nl/~rutger/software/ecos/nand-flash/


If you want FAT32, you will have to create (port from elsewhere?) a FTL (Flash Translation Layer) that implements lots of stuff to make FAT32 behave in a NAND-compatible way. For a discussion of this in the context of UBIFS (the latest-greatest Linux NAND flash file system), see:

http://www.linux-mtd.infradead.org/doc/ubifs.html#L_raw_vs_ftl

An FTL should minimally provide:
- wear levelling
- garbage collection for released blocks
- bad block management
- write caching because programming has to be consecutive and in at most a few operations.


YAFFS2 implements all this already. Is using YAFFS2 an option, maybe?

Rutger Hofman
VU Amsterdam

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