[U-Boot] Dual boot Images in Flash

[Wolfgang Denk <wd@denx.de>]

Dear pshambhu,

In message <1380633558849-164443.post@n7.nabble.com> you wrote:
>
> Can i have a small uboot_stub in the reset entry table, which will boot
> initially, and while booting it should select the default booting location
> (u-boot1).But if the default booting location fails to boot up then
> u-boot_stub should select bootloader u-boot2.
> 
> u-boot_stub will do CRC checksum on the u-boot1, if CRC checksum fails on
> that, then u-boot2 will be considered for bootup.

That would be pretty straight-forward (and I'm even tempted to write:
trivial) to implement.  Just add the CRC checking and selecting part
to SPL...

> Since its the software, i think it can be done and If it is possible, can
> you please tell me which are the files need to be taken care for the file
> changes.

On the other hand, it does not really solve your problem - how do you
fix problems or perform reliable updates of this "small uboot_stub"?

I recommend to face the real situation: yes, you can implement all
levels of complicated multi-stage boot procedures that promise to
provide all kinds of features and reliability - but in the end you
still have that small, central critical piece of code, and guess where
the nasty bug will be found?   Without hardware support (switching
boot devices etc.) you cannot implement a 100% reliable solution.  And
if it's less than 100%, then what's the difference between 99.999% and
99% ?  If things go wrong, your're stuck.  And I bet Murphy is looking
over your right shoulder right when you can't have it.

Best regards,

Wolfgang Denk

-- 
DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
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