[U-Boot] [PATCH] fw_env: add NAND support

[Wolfgang Denk <wd@denx.de>]

Dear Guennadi Liakhovetski,

In message <Pine.LNX.4.64.0809030014190.12823@axis700.grange> you wrote:
>
> If you were first setting the flag to "invalid, write in progress", then 
> wrote the environment, then reset the flag to "valid, write completed 
> successfully", then yes, writing per one write would be essentially 
> different.

But that's exactly what we are doing. The flag  value  for  "invalid,
write  in progress" is 0xFF and is set as soon as we start to destroy
the valid data by erasing the flash.

> In short, I think, CRC provides sufficient protection of data integrity.

CRC32 is not a perfect test. Yes, it's good enough for most  ordinary
cases,  but  when we can design in additional robustness we should do
this. And we should not give up what we  already  have  without  very
good reasons.

Best regards,

Wolfgang Denk

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