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Subject: Re: [PATCH] scripts/dtc: consolidate include path options in Makefile
To:     Rob Herring <robh+dt@kernel.org>
Cc:     Masahiro Yamada <yamada.masahiro@socionext.com>,
        devicetree@vger.kernel.org,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
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 <cfb66b67-f423-0c26-0b22-0d57a581b44a@gmail.com>
 <CAL_Jsq+iAxmKvZ+RAD-VSOWirYOxc52mJHU5f5gybhWwQn2w_g@mail.gmail.com>
From:   Frank Rowand <frowand.list@gmail.com>
Message-ID: <7fba348e-9fd3-9661-248d-82917f8f6676@gmail.com>
Date:   Mon, 20 Aug 2018 18:31:15 -0700
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On 08/20/18 14:32, Rob Herring wrote:
> On Mon, Aug 20, 2018 at 1:55 PM Frank Rowand <frowand.list@gmail.com> wrote:
>>
>> On 07/03/18 18:59, Masahiro Yamada wrote:
>>> It is tedious to specify extra compiler options for every file.
>>> HOST_EXTRACFLAGS is useful to add options to all files in a
>>> directory.
>>>
>>> -I$(src)/libfdt is needed for all the files in this directory
>>> to include libfdt_env.h etc. from scripts/dtc/libfdt/.
>>>
>>> On the other hand, -I$(src) is used to include check-in headers
>>> from generated C files.  Thus, I added it only to dtc-lexer.lex.o
>>> and dtc-parser.tab.o .
>>>
>>> Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
>>> ---
>>>
>>>  scripts/dtc/Makefile | 18 ++++--------------
>>>  1 file changed, 4 insertions(+), 14 deletions(-)
>>>
>>> diff --git a/scripts/dtc/Makefile b/scripts/dtc/Makefile
>>> index 9cac65b..1c943e0 100644
>>> --- a/scripts/dtc/Makefile
>>> +++ b/scripts/dtc/Makefile
>>> @@ -9,21 +9,11 @@ dtc-objs    := dtc.o flattree.o fstree.o data.o livetree.o treesource.o \
>>>  dtc-objs     += dtc-lexer.lex.o dtc-parser.tab.o
>>>
>>>  # Source files need to get at the userspace version of libfdt_env.h to compile
>>> +HOST_EXTRACFLAGS := -I$(src)/libfdt
>>
>> Shouldn't that be += instead of :=?
> 
> I don't think so. The definition is local to the file (and reset
> before each makefile is included).
> 
> Rob
> 

Every other place where HOST_EXTRACFLAGS is assigned a value, += is used
instead of :=, including the example in Documentation/kbuild/makefiles.txt

What makes scripts/dtc/Makefile different than the other makefiles?

-Frank