On Thu, Jun 02, 2016 at 08:13:51PM +0300, Pantelis Antoniou wrote: > Hi David, > > > On May 31, 2016, at 08:06 , David Gibson <david@xxxxxxxxxxxxxxxxxxxxx> wrote: > > > > On Fri, May 27, 2016 at 05:33:06PM +1000, David Gibson wrote: > >> On Tue, May 24, 2016 at 08:50:38PM +0300, Pantelis Antoniou wrote: > >>> This patch enable the generation of symbols & local fixup information > >>> for trees compiled with the -@ (--symbols) option. > >>> > >>> Using this patch labels in the tree and their users emit information > >>> in __symbols__ and __local_fixups__ nodes. > >>> > >>> The __fixups__ node make possible the dynamic resolution of phandle > >>> references which are present in the plugin tree but lie in the > >>> tree that are applying the overlay against. > >>> > >>> Signed-off-by: Pantelis Antoniou <pantelis.antoniou@xxxxxxxxxxxx> > >>> Signed-off-by: Sascha Hauer <s.hauer@xxxxxxxxxxxxxx> > >>> Signed-off-by: Jan Luebbe <jlu@xxxxxxxxxxxxxx> > >> > >> So, I think I've identified the underlying thing which was bothering > >> me about these patches. > >> > >> With the new dynamic patching stuff, "overlays" (for want of a better > >> term) now have a real existence both in the dts source format, and in > >> the dtb object format. However, these patches don't give them a > >> concrete, explicit representation within dtc itself - instead we just > >> kind of mangle one representation to the other as we're parsing. I > >> think this is a mistaken approach. > >> > >> I'm toying with some patches to give overlays a full representation in > >> dtc which I think will handle these cases better - and allow for > >> easier experimentation with different possible ways of encoding the > >> overlays. > >> > >> One side point - writing plugins in dts format leads to an irritating > >> little ambiguity in the grammar. Well, not an ambiguity technically, > >> but a place where we need more lookahead than normal, meaning we get > >> shift/reduce conflicts. It arises because both memreserves and > >> overlays can have a label in front of them. So, if we see a label as > >> our next token after the version tag, we don't know if a memreserve or > >> overlay is coming next, so the parser doesn't know which path to go > >> down (with a single token lookahead). We could handle it with > >> %glr-parser, of course, but I have been trying to avoid that. I think > >> this will apply both with your patches and with the approach I'm > >> working on - not sure what to do about it yet. > > > > I now have a first cut at said experiments, see: > > https://github.com/dgibson/dtc/tree/overlay > > > > Rebased my work and will submit again a couple of minutes. > > Everything works besides a small niggle with the overlay syntax. > > You cannot get rid of the basetree token. So… > > &foo { }; > > Does not work for an overlay, you need a dummy basetree > > / { }; &foo { }; Right, it was my intention to remove that restriction but it hits the grammar complication discussed above. I might have to bite the bullet and turn on %glr-parser. -- 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
Attachment:
signature.asc
Description: PGP signature
