[PATCH] scripts/dtc: use pkg-config to include <yaml.h> in non-standard path

From: Masahiro Yamada <masahiroy@kernel.org>
To: Rob Herring <robh+dt@kernel.org>, devicetree@vger.kernel.org
Cc: linux-kernel@vger.kernel.org,
	Masahiro Yamada <masahiroy@kernel.org>,
	Frank Rowand <frowand.list@gmail.com>
Subject: [PATCH] scripts/dtc: use pkg-config to include <yaml.h> in non-standard path
Date: Tue,  5 May 2020 19:03:19 +0900	[thread overview]
Message-ID: <20200505100319.741454-1-masahiroy@kernel.org> (raw)

Commit 067c650c456e ("dtc: Use pkg-config to locate libyaml") added
'pkg-config --libs' to link libyaml installed in a non-standard
location.

yamltree.c includes <yaml.h>, but that commit did not add the search
path for <yaml.h>. If /usr/include/yaml.h does not exist, it fails to
build. A user can explicitly pass HOSTCFLAGS to work around it, but
the policy is not consistent.

There are two ways to deal with libraries in a non-default location.

[1] Use HOSTCFLAGS and HOSTLDFLAGS for additional search paths for
    headers and libraries.
    They are documented in Documentation/kbuild/kbuild.rst

    $ make HOSTCFLAGS='-I <prefix>/include' HOSTLDFLAGS='-L <prefix>/lib'

[2] Use pkg-config

    'pkg-config --cflags' for querying the header search path
    'pkg-config --libs'   for querying the lib and its path

If we go with pkg-config, use [2] consistently. Do not mix up
[1] and [2].

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
---

 scripts/dtc/Makefile | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/scripts/dtc/Makefile b/scripts/dtc/Makefile
index ef85f8b7d4a7..0b44917f981c 100644
--- a/scripts/dtc/Makefile
+++ b/scripts/dtc/Makefile
@@ -20,6 +20,9 @@ endif
 HOST_EXTRACFLAGS += -DNO_YAML
 else
 dtc-objs	+= yamltree.o
+# To include <yaml.h> installed in a non-default path
+HOSTCFLAGS_yamltree.o := $(shell pkg-config --cflags yaml-0.1)
+# To link libyaml installed in a non-default path
 HOSTLDLIBS_dtc	:= $(shell pkg-config yaml-0.1 --libs)
 endif
 
-- 
2.25.1

