Re: [Ksummit-2013-discuss] Defining schemas for Device Tree
From: David Gibson
Date: Mon Jul 29 2013 - 21:57:52 EST
On Mon, Jul 29, 2013 at 01:23:39PM -0400, Jason Cooper wrote:
> On Mon, Jul 29, 2013 at 05:49:05PM +0100, Dave Martin wrote:
> > On Mon, Jul 29, 2013 at 11:01:24AM -0400, Jason Cooper wrote:
> > > On Mon, Jul 29, 2013 at 02:21:52AM +0200, Tomasz Figa wrote:
> > > > b) What information should be specified in schemas? What level of
> > > > granularity is required?
> > >
> > > One item I don't see in this list is node ordering. There's been some
> > > discussion lately on deferred probing (re boot times). If we were to
> > > intentionally declare that DT are parsed in the order written, then a
> > > lot of deferred probes could be avoided by moving eg the pinctrl node to
> > > near the top of the tree.
> > >
> > > This doesn't impact buses as much, since the nodes needing the bus are
> > > already children. However, anything accessed via phandles: pins,
> > > clocks, regulators, etc could benefit from declaring and enforcing this.
> > > Eg having the dtc warn when a phandle is used before it's corresponding
> > > node is declared.
> > >
> > > Not critical though, just a thought.
> > I don't think that siblings have any defined order in DT. If reading a
> > device tree, there's no guarantee you get nodes or properties out in the
> > same order as the original .dts file.
> That's why I raised the point. If people think encoding initialization
> order in the DT is a good idea, then we should change the dtc so it
> compiles/decompiles in the same order.
I'm not actually sure what you mean by this. dtc already preserves
order between input and output.
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_!
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