Re: Preventing JFFS2 partial page writes?

[Artem Bityutskiy <dedekind1@gmail.com>]

On Tue, 2011-06-28 at 12:34 +0300, Artem Bityutskiy wrote:
> OK, thanks for explanation. I am not very good in this area as I do not
> have much experience dealing with OOB, but here is what I thing.
> 
> 1. Linux MTD code was _not_ designed for "ECC'ed OOB".
> 2. I do not really know what MTD_OOB_RAW is, and the comment in mtd.h
>    is not very verbose.
> 3. But in my opinion MTD_OOB_AUTO makes most sense and should be used
>    everywhere except for some tricky cases when you want to test things
>    by writing incorrect ECC, or you have an image with ECC and you want
>    to flash it as is.
> 4. In general, OOB should be considered as belonging to the driver, and
>    modern software should not rely on OOB at all.
> 5. So MTD_OOB_AUTO make free bytes in OOB look like a contiguous buffer
>    which the _user_ can freely and _independently_ use.
> 6. In your case only this assumption does not work and your ecclayout is
>    incorrect because the OOB areas you expose are not independent.
> 7. So in your case your ecclayout should be changed and you should
>    expose only independent ECC bytes.

To put it differently, I current model does not distinguish (I think,
correct me if I am wrong) between ECC'd OOB bytes and ECC'less OOB
bytes. BTW, does your flash has the latter?

So MTD would need some work to make it distinguish between those 2 types
of OOB bytes - probably additional info could be added to the ooblayout
structure, and the interfaces could be improved. How exactly - dunno,
I'd first need to figure out what MTD_OOB_RAW is - may be Brian or Ivan
could comment.

-- 
Best Regards,
Artem Bityutskiy