Re: Merging ppc32 and ppc64

On Tue, Aug 09, 2005 at 10:01:05AM -0500, Kumar Gala wrote:

quoted

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.

That's not 100% true because as Segher said, prom_init.c is part of the
kernel (tree, image), but is what does the translation.

-- 
Tom Rini
http://gate.crashing.org/~trini/