Merging ppc32 and ppc64

Kumar Gala kumar.gala at
Wed Aug 10 01:01:05 EST 2005

> I think you are both right, just using different terminology. The
> running kernel uses its own representation of the device tree, which
> is neither the flattened stuff nor using the OF interfaces. The
> conversion from OF to the flattened tree is done by the kernel itself.
>       Apple OF  \
>           SLOF   \
>        pSeries    |-1- prom_init------,
>           PIBS   /                     \
>            ...  /                       \
>                                          \
>        other    -----------------------------2-- 
> unflatten_device_tree--3--
>    boot loader                              /
>                                            /
>        iSeries  ----------- early_setup---`
> All "regular" machines enter in the traditional prom_init path (1)
> from Open Firmware. The embedded machines that are too memory  
> constraint
> to use SLOF have a flattened device tree in their boot loader and the
> legacy iSeries boxes can fake the device tree in their  
> iSeries_early_setup
> function. The main entry point (2) is entered by all machines when the
> flattened device tree is there and the kernel builds its tree  
> representation
> for run time (3).

I guess my point is that in the "new" powerpc arch doing steps 1 & 3  
should no longer be part of the kernel proper.  The should be handled  
by boot wrappers of some form.  I know Ben tool care to ensure that  
prom_init was isolated from kernel proper and I'm suggesting we move  
it into a boot wrapper going forward.

- kumar

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