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 04:33:22PM +0100, Ahmad Fatoum wrote:
> On 09.03.23 16:28, Sascha Hauer wrote:
> > 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.
> Either you link it into barebox proper and then you should rather compress
> barebox proper itself.
> 
> Or you pick out the *.dtbo.z from the barebox build directory and in that
> case you will need decompress by hand anyway, because compressed DT
> is currently only handled for barebox live DT.

Ok, right.

Sascha

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