[PATCH v2 dtc-1.3.0] dtc: Add --strip-disabled option to dtc(v2).

[David Gibson]

B1;3202;0cOn Mon, Aug 20, 2012 at 08:25:40AM -0500, Jon Loeliger wrote:
> > From: Srinivas Kandagatla <srinivas.kandagatla at st.com>
> > 
> > This patch allows dtc to strip out nodes in its output based on status
> > property. Now the dtc has additional long option --strip-disabled to
> > strip all the nodes which do not have status property set to "okay" or
> > "ok". Nodes which do not have status property are not stripped.
> > 
> > SOCs have lot of device tree infrastructure files which mark the
> > device nodes as disabled and the board level device tree enables them if
> > required. However while creating device tree blob, the compiler can
> > exclude nodes marked as disabled, doing this way will reduce the size
> > of device tree blob. The size change will be significant once the SOC
> > adds all the possible devices in to the device trees. As there could be
> > 100s of Ips on SOCs but the board actually uses may be 20-25 IP's.
> > 
> > However care has to be taken if your boardloader is is updating status
> > property.
> > 
> > In our case this has reduced the blob size from 29K to 15K.
> > 
> > Also nodes with status="disabled" is are never probed by dt platform bus
> > code.
> > 
> > Again, this is an optional parameter to dtc, Can be used by people who
> > want to strip all the device nodes which do not have status property set
> > to "okay" or "ok".
> 
> I don't know.  This all strikes me as a means to hack around
> our total lack of a properly constructed tree based on real
> data and valid node presence.  That is, if we had a better
> means of constructing your tree in the first place, it would
> not habve 50% overhead of dead nodes.
> 
> It should be built in a positive sense, perhaps with includes, or a
> better system, and not edited out based on questionable negative data.
> 
> This just seems like a fundamentally wrong approach to me.

I'm also rather dubious about this particular use case.  On the other
hand, I don't think it's unreasonable for dtc to grow various options
to filter/mangle fdts in particular ways, even if they're only of use
fairly rarely (we already have sort, for example).  After all, dtc
already has all the code to input and output trees in various formats,
and people working with fdts will generally have dtc available.

How would you feel about a much more general version of this, which
would filter/strip nodes based on any given property=value or
property!=value condition.

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson