linux-kernel - Re: [PATCH v2 07/16] mtd/docg3: add OOB layout to mtdinfo

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Message-ID: <4EC067CE.4050805@newsguy.com>
Date:	Sun, 13 Nov 2011 16:58:54 -0800
From:	Mike Dunn <mikedunn@...sguy.com>
To:	Robert Jarzmik <robert.jarzmik@...e.fr>
CC:	dwmw2@...radead.org, dedekind1@...il.com,
	linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 07/16] mtd/docg3: add OOB layout to mtdinfo

On 11/13/2011 02:18 AM, Robert Jarzmik wrote:
> I took a different approach.  I check an internal docg3 register to see if the
> page was written. Or I could had have checked the Hamming code, as I don't think
> it can be 0xff whatever the pagesize 7 bytes values.
>
> The reason behind is that the Hamming code is Ham(64, 57), ie. Ham(2^6,
> 2^6-6-1). The means the 6 bits are enough to cover all codewords possibilities,
> and 0xff is not one of them.
>
> So unless a bitflip in Hamming code, 0xff in it means blank page.


Clever!


>  And I think
> the ECC engine is even smarter, with the ECCCONF1_PAGE_IS_WRITTEN.


I forgot about this.  If the hardware can indeed tell you, I guess this is the
best way.  Sounds like I'll be updating my blank page detection.

Mike

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