[U-Boot-Users] outline of bootm script

Wolfgang Denk
2008-08-06T20:26:52Z

In message <B754896C-6D4C-43B0-8F84-062884E569C2@kernel.crashing.org> you wrote:
>
> > Note that you cannot recover / restore after starting to uncompress
> > the image, because usually you will overwrite the exception vectors.
>
> Normally that is true.. however there are some situations that its
> feasible. For example if you are booting a kernel at a non-zero
> address. We do this on 85xx HW. Or if you are trying to boot a
> kernel on the second core of a dual core setup (at a non-zero
> address). Both of these cases we can 'bootm restore' out of.

Agreed. But compare the benefit of such a soft recovery (versus a
reset of the board) against the added complexity and irregular user
interface - on this board you can write to low RAM, on the other board
you crash the system; on one board the system recovers after a failed
attempt to load a kernel, but maybe not always, just in certain cases,
on another board it always resets the board.

KISS. Define a point of no return, and after that, recovery == reset.

> > I have to admit that I have no idea why "bootm_size" or "bootm_low"
> > are needed. If we can drop these, all the better.
>
> We use them for booting at non-zero locations.

Why is this needed?

> > "verify" and "autostart" must be kept as environment variables,
> > because that's the way how the user can influence the boot behaviour.
> > Even if you find a better way to implement this, they will be needed
> > for backward compatibility.
>
> Ok. What did we decide 'autostart' means with regards to bootm?

Yes, of course we did. It means exactly what's documented in the
manual.

Best regards,

Wolfgang Denk

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