[Yaffs-archive] [YAFFS] HW ECC Macro

[Christian Gan]

Hello all,

Ah yes YARFM (Yet Another Request For Macros)...

The current MTD I've modified enables HW ECC which means that I can insert
the ECC values into the appropriate bytes in the OOB from the MTD BUT I
can't have YAFFS trying to manipulate those bytes when it does an OOB Write
/ Read...

Charles, can we have another compile macro that disables YAFFS ECCs?  I
currently have an implementation that works, I can email it to you if you
would like.

A further problem I have to think about now is the max number of allowable
writes in the OOB.  Some NANDs allow for three writes but there are some
who's maxes are speced for two.  Which means that in my case:

  1 write to OOB by the MTD when writing a page (for HW ECC).
  1 write to OOB by YAFFS for tags.
  1 write to OOB by YAFFS to mark pages deleted.
  = 3 writes

which of course would violate some NAND specs...

What I'm thinking:
  - write a MTD level function that does the page and OOB write at the same
time.
  - somehow pass the ECC value up to the calling function from the MTD and
have higher levels write the value into OOB.
  - any other ideas?

Thanks!

Christian


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