linux-kernel - Re: [PATCH v2 2/2] mtd: spinand: micron: fixing the offset for OOB

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Date:   Wed, 23 Aug 2023 14:33:57 +0300
From:   Martin Kurbanov <mmkurbanov@...rdevices.ru>
To:     Miquel Raynal <miquel.raynal@...tlin.com>
CC:     Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        <linux-kernel@...r.kernel.org>, <linux-mtd@...ts.infradead.org>,
        <kernel@...rdevices.ru>
Subject: Re: [PATCH v2 2/2] mtd: spinand: micron: fixing the offset for OOB

Hi Miquel,

On 23.08.2023 11:41, Miquel Raynal wrote:
> Hi Martin,
>
> I don't think the four bytes have any "bad block specific" meaning. In
> practice, the datasheet states:
> 
> 	Value programmed for bad block at the first byte of spare
> 	area: 00h
> 
> So only the first byte is used to mark the block bad, the rest is
> probably marked "reserved" for simplicity. I believe we should keep the
> current layout because it would otherwise break users for no real
> reason.

I agree with you that this can break the work of users who use OOB.
However, I believe it would be more appropriate to use an offset of 4,
as the micron chip can use all 4 bytes for additional data about the
bad block. So, there is a non-zero probability of losing OOB data in
the reserved area (2 bytes) when the hardware chip attempts to mark
the block as bad.

-- 
Best Regards,
Martin Kurbanov