Re: [PATCH v2 1/7] kbuild: Add target to build dtb overlay files

[Sascha Hauer <s.hauer@pengutronix.de>]

On Thu, Mar 09, 2023 at 02:24:36PM +0100, Ahmad Fatoum wrote:
> On 09.03.23 12:52, Sascha Hauer wrote:
> > Device tree overlay files have the suffix dtso in source format
> > and dtbo in binary format. Add the necessary targets to build dtbo
> > files from dtso files and also dtbo.o files to include into the
> > barebox binary.
> > The overlay files shouldn't include the device tree snippets from
> > CONFIG_EXTERNAL_DTS_FRAGMENTS which makes it necessary to specify
> > these fragments as an argument to cmd_dtc.
> > 
> > Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
> > ---
> >  scripts/Makefile.build |  4 ++++
> >  scripts/Makefile.lib   | 11 ++++++++++-
> >  2 files changed, 14 insertions(+), 1 deletion(-)
> > 
> > diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> > index 216f03677b..33480a81b4 100644
> > --- a/scripts/Makefile.build
> > +++ b/scripts/Makefile.build
> > @@ -258,12 +258,16 @@ intermediate_targets = $(foreach sfx, $(2), \
> >  					$(filter %$(strip $(1)), $(targets))))
> >  # %.asn1.o <- %.asn1.[ch] <- %.asn1
> >  # %.dtb.o <- %.dtb.S <- %.dtb <- %.dts
> > +# %.dtbo.o <- %.dtbo.S <- %.dtbo <- %.dtso
> >  # %.dtb.pbl.o <- %.dtb.S <- %.dtb <- %.dts (Barebox only)
> > +# %.dtbo.pbl.o <- %.dtbo.S <- %.dtbo <- %.dtso (Barebox only)
> >  # %.lex.o <- %.lex.c <- %.l
> >  # %.tab.o <- %.tab.[ch] <- %.y
> >  targets += $(call intermediate_targets, .asn1.o, .asn1.c .asn1.h) \
> >  	   $(call intermediate_targets, .dtb.o, .dtb.S .dtb.z .dtb) \
> > +	   $(call intermediate_targets, .dtbo.o, .dtbo.S .dtbo.z .dtbo) \
> >  	   $(call intermediate_targets, .dtb.pbl.o, .dtb.S .dtb.z .dtb) \
> > +	   $(call intermediate_targets, .dtbo.pbl.o, .dtbo.S .dtbo.z .dtbo) \
> 
> I see now reason to allow building an overlay for PBL. Should we drop this?

I thought some board might want to apply an overlay in PBL, but the code
to apply an overlay is not there, not even the code to unflatten a dtb.
So right, this can be removed.

> 
> >  	   $(call intermediate_targets, .lex.o, .lex.c) \
> >  	   $(call intermediate_targets, .tab.o, .tab.c .tab.h)
> >  
> > diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
> > index 6e0d92cf75..6af2fe07b2 100644
> > --- a/scripts/Makefile.lib
> > +++ b/scripts/Makefile.lib
> > @@ -361,13 +361,19 @@ cmd_dt_S_dtb = $(srctree)/scripts/gen-dtb-s $(subst -,_,$(*F)) $< $(CONFIG_IMD)
> >  $(obj)/%.dtb.S: $(obj)/%.dtb $(obj)/%.dtb.z $(srctree)/scripts/gen-dtb-s FORCE
> >  	$(call if_changed,dt_S_dtb)
> >  
> > +$(obj)/%.dtbo.S: $(obj)/%.dtbo $(obj)/%.dtbo.z $(srctree)/scripts/gen-dtb-s FORCE
> > +	$(call if_changed,dt_S_dtb)
> > +
> >  $(obj)/%.dtb.z: $(obj)/%.dtb FORCE
> >  	$(call if_changed,$(suffix_y))
> >  
> > +$(obj)/%.dtbo.z: $(obj)/%.dtbo FORCE
> > +	$(call if_changed,$(suffix_y))
> 
> Can we drop this and change scripts/gen-dtb-s to skip creating the compressed DTB
> if we have a *.dtbo?

What's wrong with building compressed overlays? That might come in
handy later.

> While at, we should rename the symbol to __dtbo_. Otherwise,
> we can have name clashes.

Right.

Sascha

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