Re: gluebi and flash file systems using the OOB

Shmulik Ladkani
2012-07-25T11:26:13Z

Hi Diego,

On Wed, 25 Jul 2012 12:33:53 +0200 Diego COSTE <diego.coste@st.com> wrote:
> But we also have to use alternate flash file systems (JFFS2, YAFFS2).
> Unfortunately these file systems use the OOB and therefore can't
> directly work with the HW we use.

You should consider using UBIFS if possible.

> Then I saw that there is gluebi that re-exports a MTD, and that it is
> possible to use JFFS2 on top of it.

Gluebi exports a virtual MTD for each UBI volume.
This MTD's type is MTD_UBIVOLUME.
It is not a NAND MTD (MTD_NANDFLASH) - it does not have bad blocks,
pages, and oob part. It "resembles" NOR flash.

> Does gluebi provide an OOB emulation so that we can use *any* flash file
> system that uses the OOB ?

No.

Note JFFS2 works on top of NOR MTDs (and as such, doesn't use OOB).
So it *should* work on an MTD_UBIVOLUME as well.

However if jffs2 is mounted on MTD_NANDFLASH, it utilizes the OOB.

I remember reading something about inband tags for yaffs2.
Don't know the exact status of this; I think you should take a look.

Regards
Shmulik