On Tue, Mar 06, 2018 at 01:30:05PM +0100, Geert Uytterhoeven wrote: > Hi David, > > On Tue, Mar 6, 2018 at 4:54 AM, David Gibson > <david@xxxxxxxxxxxxxxxxxxxxx> wrote: > > On Fri, Feb 23, 2018 at 09:05:24AM +0100, Geert Uytterhoeven wrote: > >> On Fri, Feb 23, 2018 at 3:38 AM, Frank Rowand <frowand.list@xxxxxxxxx> wrote: > >> > I was hoping to be able to convert the .dts files to use sugar syntax > >> > instead of hand coding the fragment nodes, but for this specific set > >> > of files I failed, since the labels that would have been required do > >> > not already exist in the base .dts files that that overlays would be > >> > applied against. > >> > >> Indeed, hence the fixup overlays use "target-path". > >> > >> BTW, is there any specific reason there is no sugar syntax support in dtc > >> for absolute target paths? I guess to prevent adding stuff to a random > >> existing node, and to encourage people to use a "connector" API defined in > >> term of labels? > > > > Only because it hasn't been implemented. Using &{/whatever} should > > IMO generate a target-path and the fact it doesn't is a bug. > > > >> I'm also in the process of converting my collection of DT overlays to sugar > >> syntax, and lack of support for "target-path" is the sole thing that holds > >> me back from completing this. So for now I use a mix of sugar and > >> traditional overlay syntax. > >> > >> In particular, I need "target-path" for two things: > >> 1. To refer to the root node, for adding devices that should live at > >> (a board subnode of) the root node, like: > >> - devices connected to GPIO controllers provided by other base or > >> overlay devices (e.g. LEDs, displays, buttons, ...), > >> - clock providers for other overlays devices (e.g. fixed-clock). > > >> The former is the real blocker for me. > > > Below is draft patch adding target-path support. The pretty minimal > > test examples do include a case using &{/} > > > > From 8f1b35f88395adea01ce1100c5faa27dacbc8410 Mon Sep 17 00:00:00 2001 > > From: David Gibson <david@xxxxxxxxxxxxxxxxxxxxx> > > Date: Tue, 6 Mar 2018 13:27:53 +1100 > > Subject: [PATCH] Correct overlay syntactic sugar for generating target-path > > fragments > > > > We've recently added "syntactic sugar" support to generate runtime dtb > > overlays using similar syntax to the compile time overlays we've had for > > a while. This worked with the &label { ... } syntax, adjusting an existing > > labelled node, but would fail with the &{/path} { ... } syntax attempting > > to adjust an existing node referenced by its path. > > > > The previous code would always try to use the "target" property in the > > output overlay, which needs to be fixed up, and __fixups__ can only encode > > symbols, not paths, so the result could never work properly. > > > > This adds support for the &{/path} syntax for overlays, translating it into > > the "target-path" encoding in the output. It also changes existing > > behaviour a little because we now unconditionally one fragment for each > > overlay section in the source. Previously we would only create a fragment > > if we couldn't locally resolve the node referenced. We need this for > > path references, because the path is supposed to be referencing something > > in the (not yet known) base tree, rather than the overlay tree we are > > working with now. In particular one useful case for path based overlays > > is using &{/} - but the constructed overlay tree will always have a root > > node, meaning that without the change that would attempt to resolve the > > fragment locally, which is not what we want. > > > > Signed-off-by: David Gibson <david@xxxxxxxxxxxxxxxxxxxxx> > > Thank you, seems to work fine on dtc.git. > > Note that while the dtc part applies on the in-kernel copy of dtc, it > doesn't work there: "&{/}" behaves the same as "/" (i.e. no overlay > fragment is generated), but "&{/foo}" does create the overlay fragment. > Merging in Rob's for-next branch to upgrade Linux' copy of dtc fixes > that. I think that'll be because the kernel makefiles (at least by default) use a pre-generated version of the parser, rather than running bison. Since there were changes in the .y file, those will be missing which would cause the error you describe. -- 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
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