On Tue, Nov 29, 2016 at 08:45:16AM -0800, Frank Rowand wrote: > On 11/28/16 21:10, David Gibson wrote: > > On Mon, Nov 28, 2016 at 08:36:07PM -0800, Frank Rowand wrote: > >> On 11/28/16 19:10, David Gibson wrote: > >>> On Mon, Nov 28, 2016 at 06:05:39PM +0200, Pantelis Antoniou wrote: > >>>> There exists a syntactic sugar version of overlays which > >>>> make them simpler to write for the trivial case of a single target. > >> > >> It also works for multiple targets. (See the example I provided in > >> my comment to v10.) > >> > >> > >>>> > >>>> Document it in the device tree object internals. > >>>> > >>>> Signed-off-by: Pantelis Antoniou <pantelis.antoniou@xxxxxxxxxxxx> > >>> > >>> I'm with Frank that I think this, rather than being regarded mere > >>> syntactic sugar, should be considered the primary way of describing > >>> overlays. > >>> > >>> Obviously we need to support the fully written out version as well. > >> > >> If we need to support the fully written out version, can we make that > >> a discouraged, non-preferred method? Maybe require an option to > >> enable compiling this style of dts? > > > > Yeah. To avoid further proliferation of options, I'm thinking a > > single "backwards compat" option which would: > > - Use the dtb magic instead of dtb magic > > - Disable checks which would reject explicit creation of > > __overlay__ / __symbols__ / __fixups__ nodes > > - Anything other special behaviour we need > > > >> I can imagine some reasons to support the fully written out version, > >> but can we document what those reasons are? > > > > I believe the main one is the dts files in this format out in the > > field. Mind you, I guess we're already requiring them to tweak how > > they declare the /plugin/ option. > > It might be easy to write a program that transforms the expanded > format to the simple format. I'll try to make some time to see > how difficult it is. The transformation is relatively easy to > do manually, but I don't know how many dts files would need to > be converted. It's not totally trivial, because such a program would basically need a full dts parser. But.. if we change the dtc internals to work with a list of overlays rather than a single tree, there's a relatively obvious path to it: we can implement parsing a dtbo input into a set of fragments rather than an assembled overlay and dts output in fragment form. Then converting from old-dts to dtb and back to dts would pretty much do what's needed. At the cost of losing comments, though :/. -- 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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