[PATCH v2 1/2] arm/cpu/start.c: Distil some common code in __start().

[Andrey Smirnov]

>
> Previously we knew that the pointer barebox_arm_machine() works on is a
> machine type entry and we knew that the pointer returned from
> barebox_arm_boot_dtb() is a dtb. With this patch both are share the same
> pointer so we would have to check if the result returned from
> barebox_arm_boot_dtb() is actually a dtb. That's not so nice.

That is only partially true. The code before this patch assigned the
value of `boarddata` to `barebox_boarddata` unconditionally before it
did any checks of the contents validity, so there were no real
guarantees about barebox_arm_machine().

And we can add those checks to the code of barebox_arm_machine() and
barebox_arm_boot_dtb() and restore the original semantics.

>
> Sascha
>
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