OOB Location

OOB Location

[Ajay Jain]

Hi All, 

I have one question regarding JFFS2 on NAND flash. My hardware has a
NAND flash controller, which does automatic error correction. It needs
10 bytes for this, which it stores in the OOB area of each page. JFFS2
also stores some information in this area, from locations 8-15 for a 512
page-size NAND flash. Now the issue is that the storage locations as
used by our hardware and JFFS2 clash. My first hunch is that its a
quirky hardware. My questions is:
Is it possible to use some other location for storing file-system
information. Is there an option, so that JFFS2 can store this
information in some other area? If yes, how to use this. I saw the
'mkfs.jffs2' help, it does not expose any such option. 

Thanks.
Ajay 

 

Re: OOB Location

[Thomas Gleixner]

On Sat, 2006-09-16 at 18:56 +0530, Ajay Jain wrote:
> I have one question regarding JFFS2 on NAND flash. My hardware has a
> NAND flash controller, which does automatic error correction. It needs
> 10 bytes for this, which it stores in the OOB area of each page. JFFS2
> also stores some information in this area, from locations 8-15 for a 512
> page-size NAND flash. Now the issue is that the storage locations as
> used by our hardware and JFFS2 clash. My first hunch is that its a
> quirky hardware. My questions is:

That's supported. JFFS2 puts the cleanmarker into the bytes which are
not used by ECC.

static struct nand_ecclayout rtc_from4_nand_oobinfo = {
	.eccbytes = 32,
	.eccpos = {
		   0, 1, 2, 3, 4, 5, 6, 7,
		   8, 9, 10, 11, 12, 13, 14, 15,
		   16, 17, 18, 19, 20, 21, 22, 23,
		   24, 25, 26, 27, 28, 29, 30, 31},
	.oobfree = {{32, 32}}
};

JFFS2 puts the cleanmarker at offset 32 in OOB.

> Is it possible to use some other location for storing file-system
> information. Is there an option, so that JFFS2 can store this
> information in some other area? If yes, how to use this. I saw the
> 'mkfs.jffs2' help, it does not expose any such option. 

mkfs.jffs2 does not know anything about the OOB usage scheme at all.

	tglx