[PATCH] mtd: nand: add option to erase NAND blocks even if detected as bad.

[Mario Rugiero]

2017-05-12 5:12 GMT-03:00 Richard Weinberger <richard.weinberger at gmail.com>:
> Mario,
>
> On Fri, May 12, 2017 at 7:39 AM, Mario J. Rugiero <mrugiero at gmail.com> wrote:
>> Some chips used under a custom vendor driver can get their blocks
>> incorrectly detected as bad blocks, out of incompatibilities
>> between such drivers and MTD drivers.
>> When there are too many misdetected bad blocks, the device becomes
>> unusable because a bad block table can't be allocated, aside from
>> all the legitimately good blocks which become unusable under these
>> conditions.
>> This adds a build option to workaround the issue by enabling the
>> user to free up space regardless of what the driver thinks about
>> the blocks.
>
> Hmm, this sounds like a gross hack.
It is, but I see no other solution. The NAND chips were used in an
incompatible way by a hack-n-slash driver made by allwinner, and
trying to load them with a proper MTD driver fails miserably if this
is not done.
If anyone can propose a better solution I'll more than happily implement it.
I'm open to suggestions, and of course I'm open to rejection of my
patches if needed.
>
>> Example usage: recovering NAND chips on sunxi devices, as explained
>> here: http://linux-sunxi.org/Mainline_NAND_Howto#Known_issues
>
> What this wiki suggests is not wise.
> How can you know which blocks are really bad and which not?
You don't, at least not without an even grosser hack implementing read
support for their incompatible format.
Would that be better? I might attempt it if desired.
>
> --
> Thanks,
> //richard