linux-kernel - Re: [PATCH] cmd_dtc: Enable generation of device tree symbols

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Message-ID: <75be8210-ff70-51cb-11f1-bd012ac7fb94@gmail.com>
Date:   Tue, 26 Jan 2021 12:02:40 -0600
From:   Frank Rowand <frowand.list@...il.com>
To:     Masahiro Yamada <masahiroy@...nel.org>,
        Uwe Kleine-König <uwe@...ine-koenig.org>,
        Frank Rowand <frowand.list@...il.com>
Cc:     Michal Marek <michal.lkml@...kovi.net>,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        cyril@...amax.com, Arnd Bergmann <arnd@...db.de>,
        Maxime Ripard <mripard@...nel.org>,
        DTML <devicetree@...r.kernel.org>
Subject: Re: [PATCH] cmd_dtc: Enable generation of device tree symbols

+frank

On 1/25/21 3:53 PM, Masahiro Yamada wrote:
> On Mon, Jan 25, 2021 at 8:07 PM Uwe Kleine-König <uwe@...ine-koenig.org> wrote:
>>
>> Adding the -@ switch to dtc results in the binary devicetrees containing
>> a list of symbolic references and their paths. This is necessary to
>> apply device tree overlays e.g. on Raspberry Pi as described on
>> https://www.raspberrypi.org/documentation/configuration/device-tree.md.
>>
>> Obviously the downside of this change is an increas of the size of the
>> generated dtbs, for an arm out-of-tree build (multi_v7_defconfig):
>>
>>         $ du -s arch/arm/boot/dts*
>>         101380  arch/arm/boot/dts-pre
>>         114308  arch/arm/boot/dts-post
>>
>> so this is in average an increase of 12.8% in size.
>>
>> Signed-off-by: Uwe Kleine-König <uwe@...ine-koenig.org>
> 
> 
> (CCing DT ML.)
> 
> 
> https://www.spinics.net/lists/linux-kbuild/msg27904.html
> 
> See Rob's comment:
> 
> "We've already rejected doing that. Turning on '-@' can grow the dtb
> size by a significant amount which could be problematic for some
> boards."
> 
> 
> 
> 
> 
> 
> 
> 
>> ---
>>  scripts/Makefile.lib | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
>> index 213677a5ed33..0683a5808f7f 100644
>> --- a/scripts/Makefile.lib
>> +++ b/scripts/Makefile.lib
>> @@ -319,7 +319,7 @@ $(obj)/%.dtb.S: $(obj)/%.dtb FORCE
>>
>>  quiet_cmd_dtc = DTC     $@
>>  cmd_dtc = $(HOSTCC) -E $(dtc_cpp_flags) -x assembler-with-cpp -o $(dtc-tmp) $< ; \
>> -       $(DTC) -O $(patsubst .%,%,$(suffix $@)) -o $@ -b 0 \
>> +       $(DTC) -@ -O $(patsubst .%,%,$(suffix $@)) -o $@ -b 0 \
>>                 $(addprefix -i,$(dir $<) $(DTC_INCLUDE)) $(DTC_FLAGS) \
>>                 -d $(depfile).dtc.tmp $(dtc-tmp) ; \
>>         cat $(depfile).pre.tmp $(depfile).dtc.tmp > $(depfile)
>> --
>> 2.29.2
>>
> 
> 
> --
> Best Regards
> 
> Masahiro Yamada
>