On Wed, 2007-03-21 at 19:06, David Gibson wrote:

I mean, does the u-boot source tree have its own copies of the dts
files which are built into a dtb during the u-boot build process?

There are not DTS files in U-Boot anymore.  They are all
currently in the arch/powerpc/boot/dts directory, or some
other private home directory. :-)

  Or
do you take the dts from the kernel tree and make the dtb from that

yes.

when you build a dtb aware u-boot for a particular machine?

Do it whenever you want.  But it has to be downloaded
to RAM or found in flash on the board by U-Boot by the
time you want to do the hand-off to Linux.  That is,
there is no need to "combine" it with U-Boot to make
it "dtb aware".  U-Boot is still built independently of
any DT[SB] file entirely.

quoted

Ok, I understand now, but I don't know what value it has.  I don't see 
the difference, from the DTS point-of-view, between

	local-mac-address = [ 00 00 00 00 00 00 ]
and
	local-mac-address = [ ? ? ? ? ? ? ];

In terms of the generated dtb output there is no difference.  Well,
probably.  It would It's
purely syntactic sugar / internal documentation.

Right.  It is more like "make it clear to the DTS file
reader that these fields are intended to be filled in by
the bootloader".

Well, no.  You wanted to get rid of the property from the dts, I
didn't.  What I'm suggesting here is an idea to addresses at least one
possible objection to having the properties in the dts: the fact that
with actual values there it looks like the tree is complete and it
might not be obvious that a bootloader *must* tweak values to produce
a working tree.

(nit) But let's not forget that there are cases where we _do_ want
the DTS to be complete too.

I think it's useful to document in the dts that certain properties are
expected to be there, even if their actual values have to be
determined during boot.  This syntax allows a dts to show to someone
reading it that a property is expected, and what its expected size is,
but that the value must be filled in later.  It's for the benefit of
people reading the dts, not programs.

Exactly.

jdl