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From: Segher Boessenkool <segher@kernel.crashing.org>
Subject: Re: common flatdevtree code
Date: Thu, 28 Sep 2006 01:41:27 +0200
To: Paul Mackerras <paulus@samba.org>
Cc: linuxppc-dev <Linuxppc-dev@ozlabs.org>,
	Hollis Blanchard <hollisb@us.ibm.com>
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> I talked to David Gibson about this and he pointed out that there is a
> problem with using a void * to identify nodes (i.e. returned from
> ft_find_device and passed to ft_set_prop etc.).  The problem is that
> if we reallocate the space for the tree, then any void * handles that
> the user of the library has are then invalid.  Perhaps we have to use
> offsets from the beginning of the struct region instead - the offset
> for a node will be stable across changes of the node or any of its
> descendents, at least.

Or unpack the tree before you operate on it.  You can pack it
again later if you need to pass it as a flat tree again (or the
bootwrapper could implement a real OF client interface, which
is useful for many more things!)

A flat contiguous blob of bytes is convenient to pass around,
but not such a great data structure for basically anything else ;-)


Segher