Hi Charles,

Thanks for the info.
I'm going over the code right now, I found the ecc layout structs.
My question is: where can I find out the addresses yaffs writes to?
I saw 

int nandmtd2_WriteChunkWithTagsToNAND(yaffs_Device *dev, int
chunkInNAND, const __u8 *data, const yaffs_ExtendedTags *tags)

has some calls to mtd->write_oob(mtd, addr, &ops); 
and started printing the addr out but then I wondered what exactly the
addr means. Is it a real address in the chip or is it some kind of
offset?
I know I'm a bit lost here, and would very much appreciate your help.

Thanks,

Boaz.


On Thu, 2010-12-30 at 11:06 +1300, Charles Manning wrote:
> On Tuesday 28 December 2010 06:38:17 Ross Younger wrote:
> > * Boaz Ben-David <boaz.bd@wellsense-tech.com> wrote:
> > > My problem is that when I try to write some files (even using "touch")
> > > it seems yaffs is trying to retire all of the blocks on the partition.
> >
> > Most problems I've encountered of this nature have been caused by bugs in
> > the MTD driver(s). The root causes have been things like the MTD driver
> > misreporting to YAFFS that the write failed, the write actually failing
> > due to a protocol or timing error, or YAFFS believing there to be an
> > ECC mismatch somewhere along the line. Particularly check the ECC -
> > sometimes you have to special-case the check for empty pages (if the
> > ECC for an erased block - all 0xFF - is not itself all 0xFF).
> >
> > You may be able to get more of an insight into exactly what has gone
> > wrong by turning on tracing and working backwards from the exact error
> > reported.
> >
> > Ross
> 
> Ross is almost certainly right.
> 
> The nand oob/spare area is generally split into three areas:
> * bad block marker - typically 2 bytes at offset 0
> * ECC bytes.
> * oobferee used by yaffs to store tags.
> 
> Eg there is a typical oob layout structure:
>   
> static struct nand_ecclayout nand_oob_64 = {
>         .eccbytes = 24,
>         .eccpos = {
>                    40, 41, 42, 43, 44, 45, 46, 47,
>                    48, 49, 50, 51, 52, 53, 54, 55,
>                    56, 57, 58, 59, 60, 61, 62, 63},
>         .oobfree = {
>                 {.offset = 2,
>                  .length = 38}}
> };
> 
> The structure starts at offset 2 because the first two bytes are used by the 
> bad block marker.
> 
> The yaffs tags reading/writing should be accessing oobfree.
> 
> Some drivers get this wrong and reads/writes that should be accessing the 
> oobfree areas are instead accessing some other area. A typical mistake is to 
> not apply the layout and just access at offset 0. This causes problems 
> because the tags and bad block marker get mashed together.
> 
> I suggest you work through the function calls to check that the right bytes 
> are being accessed.
> 
> --- Charles