Re: [SPAM] FAT on NAND

["Jim Zeus" <jimzeus@vip.sina.com>]

> > What I am doing now is to build a filesystem which can be
> > recognized on _raw_ NAND flash. So, I think FAT will be the only
> > choice(though I know it's very unstable). And I have following question
> > now:
> For what ? Why don't you use JFFS2 or YAFFS, which handle NAND out of the box 
> ?

Because I've got to build a FS which can be accessed by Windows and Linux at the same 
time.I think JFFS2/YAFFS can't be recognized by Windows nowadays. 
And , it seems like I have to support some device layer between the FS and Flash so the
Linux can access it, isn't it?
Is there anyway else I can choose?

> 
> > 1.How unstable would it be? Does it support:
> >      a.journaling (crash/power-off safe ,I mean)
> >      b.bad block management
> >      c.wear levelling
> >      d.error correction
> >      e.something else I dont know to make the FS reliable
> JFFS2 and YAFFS have all this, read the source and build a new one, if you 
> have enough time.

Are all the functions supported by JFFS2/YAFFS? Somebody told me the wear levelling
is supported by MTD

And It seems like I don't have enough time ,maybe I can finish it with all my leisure time.

> > 4.Everybody tells me that the Fat on a NAND is not reliable,but I
> > think USB mass storage are based on NAND and got a FAT (or some
> > filesystem which windows can recognize) on it, so ,how comes it
> > happen?
> Yes, this is Smart-Media-FAT, which is not exactly the same as DOS-FAT. 
> SmartMedia-FAT is used on SmartMedia cards for MP3-Players, Digicams ... 
> There exist various adapters (USB, serial, LPT) to access it via a PC. 
> SmartMedia-FAT is designed for NAND-FLASH and handles bad block management 
> and error correction. 
> If you want compability to this, you have to write a fs-driver, which is 
> compatible to the SMART-Media-FAT definition, which is available from Toshiba 
> under a non disclosure aggreement. 

Does the SMART-Media-FAT build directly on a _bare_ NAND Flash ? 
If it is, That's nothing useful to me 'cause Linux cant access it.


Thanks a lot for answering my questions

Your Faithful
Jim Zeus