[PATCH 3.16.y-ckt 172/180] tools/power turbostat: Use $(CURDIR) instead of $(PWD) and add support for O= option in Makefile

[Luis Henriques]

3.16.7-ckt11 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Thomas D <whissi@xxxxxxxxx>

commit f82263c6989c31ae9b94cecddffb29dcbec38710 upstream.

Since commit ee0778a30153
("tools/power: turbostat: make Makefile a bit more capable")
turbostat's Makefile is using

  [...]
  BUILD_OUTPUT    := $(PWD)
  [...]

which obviously causes trouble when building "turbostat" with

  make -C /usr/src/linux/tools/power/x86/turbostat ARCH=x86 turbostat

because GNU make does not update nor guarantee that $PWD is set.

This patch changes the Makefile to use $CURDIR instead, which GNU make
guarantees to set and update (i.e. when using "make -C ...") and also
adds support for the O= option (see "make help" in your root of your
kernel source tree for more details).

Link: https://bugs.gentoo.org/show_bug.cgi?id=533918
Fixes: ee0778a30153 ("tools/power: turbostat: make Makefile a bit more capable")
Signed-off-by: Thomas D. <whissi@xxxxxxxxx>
Cc: Mark Asselstine <mark.asselstine@xxxxxxxxxxxxx>
Signed-off-by: Len Brown <len.brown@xxxxxxxxx>
Signed-off-by: Luis Henriques <luis.henriques@xxxxxxxxxxxxx>
---
 tools/power/x86/turbostat/Makefile | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/tools/power/x86/turbostat/Makefile b/tools/power/x86/turbostat/Makefile
index d1b3a361e526..4039854560d0 100644
--- a/tools/power/x86/turbostat/Makefile
+++ b/tools/power/x86/turbostat/Makefile
@@ -1,8 +1,12 @@
 CC		= $(CROSS_COMPILE)gcc
-BUILD_OUTPUT	:= $(PWD)
+BUILD_OUTPUT	:= $(CURDIR)
 PREFIX		:= /usr
 DESTDIR		:=
 
+ifeq ("$(origin O)", "command line")
+	BUILD_OUTPUT := $(O)
+endif
+
 turbostat : turbostat.c
 CFLAGS +=	-Wall
 CFLAGS +=	-DMSRHEADER='"../../../../arch/x86/include/uapi/asm/msr-index.h"'
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