[PATCH v2] selftests: gpio: fix Makefile

[Fathi Boudra]

* Fix hardcoded and misplaced libmount headers. Use pkg-config instead to
  figure out CFLAGS/LDLIBS, fixing also their value for cross-compilation.
  Note: if pkg-config is missing (command not found), it will fail to
  build because headers can't be found or libmount library can't be
  linked.

* Fix the clean target to clean up also gpio-utils.

* Fix gpio-mockup-chardev installation by using TEST_PROGS_EXTENDED
  instead of BINARIES which is not supported by the top-level lib.mk.

* Get rid of INSTALL_HDR_PATH. We don't need it since make -C is putting
  us in the right location.

* Improve readibility:
  - introduce GPIODIR/GPIOOBJ/GPIOINC variables
  - split CFLAGS on multiple lines

Signed-off-by: Fathi Boudra <fathi.boudra@xxxxxxxxxx>
---

in v2:
 * per Michael Ellerman request, revert to use exported headers instead of uapi.

 tools/testing/selftests/gpio/Makefile | 31 ++++++++++++++++++-------------
 1 file changed, 18 insertions(+), 13 deletions(-)

diff --git a/tools/testing/selftests/gpio/Makefile b/tools/testing/selftests/gpio/Makefile
index 205e4d10e085..41826897af35 100644
--- a/tools/testing/selftests/gpio/Makefile
+++ b/tools/testing/selftests/gpio/Makefile
@@ -1,23 +1,28 @@
+CFLAGS += -O2 -g -std=gnu99 -Wall
+CFLAGS += -I../../../../usr/include/
+CFLAGS += $(shell pkg-config --cflags mount)
+LDLIBS += $(shell pkg-config --libs mount)
 
 TEST_PROGS := gpio-mockup.sh
-TEST_FILES := gpio-mockup-sysfs.sh $(BINARIES)
-BINARIES := gpio-mockup-chardev
+TEST_PROGS_EXTENDED := gpio-mockup-chardev
+TEST_FILES := gpio-mockup-sysfs.sh
+
+GPIODIR := ../../../gpio
+GPIOOBJ := gpio-utils.o
+GPIOINC := gpio.h
 
 include ../lib.mk
 
-all: $(BINARIES)
+all: $(GPIOINC) $(TEST_PROGS_EXTENDED)
 
 clean:
-	$(RM) $(BINARIES)
-
-CFLAGS += -O2 -g -std=gnu99 -Wall -I../../../../usr/include/
-LDLIBS += -lmount -I/usr/include/libmount
-
-$(BINARIES): ../../../gpio/gpio-utils.o ../../../../usr/include/linux/gpio.h
+	$(RM) $(TEST_PROGS_EXTENDED)
+	$(MAKE) -C $(GPIODIR) clean
 
-../../../gpio/gpio-utils.o:
-	make ARCH=$(ARCH) CROSS_COMPILE=$(CROSS_COMPILE) -C ../../../gpio
+$(TEST_PROGS_EXTENDED): $(GPIODIR)/$(GPIOOBJ)
 
-../../../../usr/include/linux/gpio.h:
-	make -C ../../../.. headers_install INSTALL_HDR_PATH=$(shell pwd)/../../../../usr/
+$(GPIODIR)/$(GPIOOBJ):
+	$(MAKE) -C $(GPIODIR)
 
+$(GPIOINC):
+	$(MAKE) -C ../../../.. headers_install
-- 
2.11.0