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Re: Re: RE : JFFS2 for NAND flash file system


On 06/01/2011 04:43 PM, Paul MAILLET wrote:
>
> Hi,
>
> So the FS has to be aware of the NAND device. Plus, with this
>
I think most FS's are aware of the HW below. FAT was designed for a HD 
(a rotating mechanical disk with cylinders ..), not for a flash device 
(silicon chip, with erase sectors, writing means first erasing to all 
1's, and flipping the needed bits to 0). Of course you can make a 
translation layer for compatibility at the cost of efficiency.
But flash is
>
> abstraction layer using a journaled file system (like JFFS) will
> introduce twice wear levelling... Thanks for the help.
>
why twice? NAND support on JFFS2 just adds (or should add, I don't know) 
some extra things needed for NAND on top of JFFS2-designed-for-NOR flash 
(ECC and BBT (bad block table)).
>
>
> Anyway, I need to go deeper with my eCos configuration here.
> I succeeded in running JFFS2, but I am totaly unable to tell which
> version it is, if it support NAND or not in this version or
> anything...
> I didn't found anything about the version I currently use, and more
> it's quite disturbing to find these lines in the TODO's file from the
> JFFS2 package (even in the v3.0 release version):
>
> [...]
>  - NAND flash support:
>         - almost done :)
>         - use bad block check instead of the hardwired byte check
> [...]
>
> All I can tell is that sources from the JFFS2 package I use are mostly
> post 2004 with version like 1.1xx.
>
I guess you need to check linux jffs2, maybe mail the mtd mailing list.
I remember a ask-for-support mail to update the JFFS2 in eCos.
>
>
> How can I ensure that my version support NAND?
>
Ask in a separate mail if anybody has done it before..
>
> Is there any tests I can run to validate the FS?
>
Use (T)FTP and read/write/overwrite/erase files until the FS is full, 
with big or small files, over and over again, for days, weeks, without 
power cycling or unmounting. And check the heap status.
>
>
> Thanks for your time,
> Best regards,
> Paul
>
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> Before posting, please read the FAQ: http://ecos.sourceware.org/fom/ecos
> and search the list archive: http://ecos.sourceware.org/ml/ecos-discuss
>


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