RE: [Yaffs] Changing internal YAFFS ECC?

> -----Original Message-----
> From: yaffs-bounces@lists.aleph1.co.uk
> [mailto:yaffs-bounces@lists.aleph1.co.uk] On Behalf Of Wookey
> Sent: 13 September 2006 19:12
> To: yaffs@lists.aleph1.co.uk
> Subject: [Yaffs] Changing internal YAFFS ECC?
>
> On 06-09-13 19:31 +0400, Vitaly Wool wrote:
> > On 9/13/06, Wookey <wookey@aleph1.co.uk> wrote:
> >
> > >Yes. Yaffs needs to be able to do it's own ECC for YAFFS/direct
or
> > >indeed any other situation where there isn't something
> else like MTD
> > >to do the work for it.
> >
> > Oh I see the problem now.
> > I think however that the best thing to do here is to use the same
> > 'default' OOB layouts MTD uses so that the ECC bytes were placed
in
> > OOB in the same way. If that solution is fine for you, YAFFS own
ECC
> > can still be used on most flashes, with some precautions though.
>
> YAFFS internal ECC layout came from compatibilty with smartmedia
> layout (IIRC). This is fairly arbitrary (and unfortunately different
> to MTD layout). I'm not sure how much aggravation we will cause
> existing (non-linux) users by changing it now. I wonder if it is
> better to keep the layout as is but simply not use it with Linux
2.6,
> or to change to be the same as MTD.
>
> The former avoids Linux problems so long as the docs are clear, and
> makes no change for non-linux users.
>
> The latter means linux people can swap between MTD and (slightly
> faster?) yaffs ECC easily. But non-linux users will not be able to
use
> exisiting filesystems with new YAFFS2.
>
> How serious would a non-backwards compatible OOB layout change be
for
> existing YAFFS2/direct users? Feedback welcome.
>
> Wookey
> --

As a direct user I don't think it would be an issue. Direct
applications are usually placed in embedded products and sold that
way. Once the product, e.g. video recorder, is out in the field and
some bugs needs to be fixed the existing code will be modified and
distributed as, e.g., a hex file. This means the existing yaffs
version will be packed in that hex file and will be able to read
whatever is stored on the flash of that product.

When a new product is designed the new yaffs version can be used but
it won't have to read any 'old' flash chips.

Johann Kok

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