Re: [Yaffs] bit error rates --> a vendor speaks

Josh Boyer
2006-02-21T13:50:47Z

On 2/21/06, Artem B. Bityutskiy <dedekind@yandex.ru> wrote:
> Charles Manning wrote:
> > Sorry Thomas I don't buy that argument. If a system has a NAND device that
> > does have spare OOB available then it does have spare OOB and I can rely on
> > that. If a NAND chip is soldered to a board, and the system exposes the OOB
> > it is there. YAFFS (or whatever) can then be used on this device.
>
> I understand Thomas's point as as he is fighting for generalization.
> Indeed, this OOB stuff introduces a lot of mess.
>
> Charles' point is - if OOB is there, why not to let users use it? Also
> sounds reasonable.

But Charles also wants clean interfaces. I agree that clean
interfaces are definitely a good thing, but trying to come up with a
clean interface for OOB access that won't get bastardized seems to be
unattainable.

> What I think would be nice to do is to get rid of OOB in MTD stuff, but
> add a possibility to access OOB via some NAND-specific interfaces from
> nand_base. Indeed, if one wants to work with a generalized flash device
> - please use MTD interface. If one still wants to access OOB, use
> lower-layer NAND interfaces. That's all about to have more then one
> layer of Generalization. And I believe this is the right way to go.

I think at some time in the not so distant future this whole
conversation will become a moot point. SLC NAND quality seems to be
degradding as the die sizes go down, and MLC NAND is already of a
degraded quality comparitively. Better ECC algorithms will be needed
to provide the reliability that people want and I can see that
consuming all of the available OOB area anyway.

josh