nand_default_bbt and x8 large page nand devices

Nishanth Menon menon.nishanth at
Mon Jan 5 15:27:14 EST 2009

Looping in mtd list on this.

On Mon, Jan 5, 2009 at 2:01 PM, Scott Wood <scottwood at> wrote:
> On Wed, Dec 31, 2008 at 03:31:41PM -0600, Nishanth Menon wrote:
>> A gentle question on drivers/mtd/nand/nand_bbt.c:largepage_flashbased
>> in Micron devices, the bb marker is the first word. for a x8 device is
>> 1 byte and x16 device it is 2 bytes. .len = 2 makes sense for an x16
>> device in the above variable, however the marker does a false postive
>> detection for x8 devices.
> Right, simplest way to work around this is to just keep the first two
> bytes reserved even on x8 devices.  If you need to maintain compatibility
> with a map that doesn't do that, then override the badblock pattern in
> the driver as you describe.
>> I can over ride this by using nand_chip->badblock_pattern in my board
>> file, but from an mtd layer perspective, does it make sense to fix
>> this for a generic usage?
> Possibly, but that's not a point on which I want to deviate from Linux.
> Feel free to try to get it changed there.

I guess the real question could be: is this a bug in reality? Do all x8 large
page devices expect 1 byte bb marker or is it just micron?

Nishanth Menon

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