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

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

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.

Cheers,
Ahmad 

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

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