Author: Ian McDonnell Date: To: yaffs Subject: Re: [Yaffs] Re: [YAFFS1] Some bits are changed - systematically
On Tuesday 29 November 2005 09:28, Martin Egholm Nielsen wrote: > Can this occur, say, with a bad NAND? Would YAFFS/MTD puke up
> with a lot of checksum errors?
The most you could hope for is an uncorrected ECC. ECC can
correct a single bit error within each 256 byte sub-page block
of data. If the data was corrupted on the way out to flash,
before the ECC was calculated, the ECC will be consistent with
the data, if the corruption happen 'below ECC', say on the chip
or i/o to/from the chip, then the ECC should be inconsistent
with the data. If you can figure out the physical block/page
address of the offending data, you could instrument the ECC code
(in MTD) to show how the stored data and stored ECC measures up.
If the ECC is good, then the corruption very probably happened
'above' the ECC when the data was written. None of the above
really answers the question of how/what introduced the
corruption, it just narrows the scope.
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