[RFC] dtc: Optionally sort nodes and properties

[Scott Wood]

On Wed, 8 Sep 2010 14:25:30 -0600
Grant Likely <grant.likely at secretlab.ca> wrote:

> On Wed, Sep 01, 2010 at 12:47:18PM +1000, David Gibson wrote:
> > Hi folks,
> > 
> > Here's a patch I made for dtc a little while ago, and I'm not sure if
> > it's something that sensibly ought to be merged into mainline dtc.
> > 
> > The patch adds a '-s' option to dtc, which causes it to "sort" the
> > tree before output.  That is, it sorts the reserve entries, it sorts
> > the properties within each node by name, and it sorts nodes by name
> > within their parent.
> > 
> > The main use for this is when looking at the differences between two
> > device trees which are similar, except for semantically null internal
> > rearrangements.  Directly diffing the dts files will give a lot of
> > noise due to the order changes, but running both trees through dtc -s
> > then diffing will usually give a pretty sensible summary of the
> > changes (it can still be confused by node name changes, of course).
> 
> As discussed on IRC, I'm not thrilled with adding this as a
> user-visible option because sorted trees aren't actually useful or
> desirable (and in some cases undesireable) except for the use-case of
> comparing trees.  However, being able to compare unsorted trees is
> still a use case that is very much needed, so I'm okay with this patch
> until we come up with something better.
> 
> Although maybe the -s option should remain undocumented; or at least
> warn people away from using it.

If it's undocumented, how would people find out how to compare device
trees?

Maybe just add a "(for comparing trees)" note in the help text to
clarify the intended purpose?

-Scott