nandwrite and contiguous space

[Stas Sergeev]

01.04.2014 22:23, Gerhard Sittig пишет:
> On Tue, 2014-04-01 at 13:30 +0400, Stas Sergeev wrote:
>> I am looking for a NAND flasher that supports searching
>> for the contiguous region of good blocks (within a specified
>> range), and flashes an image to it. It seems nandwrite - the
>> default linux flasher - can only skip bad blocks, but the scenario
>> I need, doesn't seem to be supported.
> Isn't the point that the set of good blocks keeps changing over
> time?  What might be good now, may be bad a second later or next
> year, doesn't matter as long as it won't stay good forever.
Hi, I think the point is that if they are no longer ever written,
they won't change its goodness...
Anyway, this is how the ST soc chips work.
They search NAND for a specific signature, and once
found, they map the contiguous block, starting from
that signature, to memory, which allows to run u-boot
in a nor-alike fashion. They do not do BBT lookups when
mapping, AFAIK, and so such a requirement for flasher
does exist.

>> Is there any other flasher that does support this?
>> Or maybe some trick with nandwrite exists?
>> If not, how difficult is it to implement such a capability into
>> nandwrite?
> If you want a sequence of good blocks, this very much sounds like
> the LEBs which UBI provides.  Aren't you asking for an UBI
> volume?  What am I missing?
Unfortunately, I don't think the aforementioned ST chips
can boot from UBI. Once booted, I want UBI for sure.
But the only alternative to the aforementioned requirement
would be to assume that 2 first blocks are good, and fit
u-boot there, and it they are bad - throw away such a nand.
I am considering this too, but I wonder how many nands
will be wasted this way... Likely none, but who knows. :)