[PATCH] powerpc/bootwrapper: Add documentation of boot wrappertargets

[Stephen Neuendorffer]

> -----Original Message-----
> From: Josh Boyer [mailto:jwboyer at gmail.com]
> Sent: Thursday, June 26, 2008 12:07 PM
> To: Stephen Neuendorffer
> Cc: grant.likely at secretlab.ca; John Linn; linuxppc-dev at ozlabs.com;
paulus at samba.org;
> petermendham at computing.dundee.ac.uk
> Subject: RE: [PATCH] powerpc/bootwrapper: Add documentation of boot
wrappertargets
> 
> On Thu, 2008-06-26 at 09:48 -0700, Stephen Neuendorffer wrote:
> > My unanswered questions:
> >
> > 1) Why are there 4 different types of targets that embed a device
tree?
> > I assume they differ in how they are started loaded, but
(unfortunately)
> > the names are meaningless (With the exception of cuImage, which is
only
> > cryptic.. :)  If I'm adding support for a new board, which should I
use?
> 
> They are all needed to deal with different firmwares.

Where 'firmware' really means 'method of invoking the kernel'

> treeImage is for OpenBIOS based boards (Ebony, Walnut, some boards
> running PIBS can also use this).  This firmware requires a special
> header on the image file.

So it's not an elf? or it is an .elf?  maybe it should be
'openBiosImage'?
 
> cuImage is for boards running an older U-Boot that does not understand
> device trees.

Forgive my ignorance here, but what specifically does this imply?  As
far as I can tell, generally speaking, some of the board-specific
information is passed into the boot wrapper, which then stuffs it into
the device tree.

> uImage is for device-tree aware U-Boot versions

And this differs from above because it gets a device tree passed in,
which uboot has already stuffed correctly.

> dtbImage is used for boards that can take an ELF zImage, but still
need
> a dtb provided.
> 
> simpleImage, not sure here.

So both of these are elfs...  but how do they differ?  Is it only in how
the right head.s file gets picked up?

Steve


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