2 files changed, 23 insertions, 0 deletions

diff --git a/Makefile b/Makefile
index cfbe0e994..7c00ce2cc 100644
--- a/Makefile
+++ b/Makefile
@@ -59,6 +59,12 @@ ifndef KEYBOARD
         KEYBOARD=planck
 endif
 
+MASTER ?= left
+ifdef master
+        MASTER = $(master)
+endif
+
+
 # converts things to keyboards/subproject
 ifneq (,$(findstring /,$(KEYBOARD)))
         TEMP:=$(KEYBOARD)
@@ -212,6 +218,14 @@ ifeq ($(strip $(SERIAL_LINK_ENABLE)), yes)
         VAPTH += $(SERIAL_PATH)
 endif
 
+ifeq ($(MASTER),right)  
+        OPT_DEFS += -DMASTER_IS_ON_RIGHT
+else 
+        ifneq ($(MASTER),left)
+$(error MASTER does not have a valid value(left/right))
+        endif
+endif
+
 # Optimize size but this may cause error "relocation truncated to fit"
 #EXTRALDFLAGS = -Wl,--relax
 
diff --git a/tmk_core/common.mk b/tmk_core/common.mk
index d71fba9bc..5bae0d762 100644
--- a/tmk_core/common.mk
+++ b/tmk_core/common.mk
@@ -97,6 +97,15 @@ ifeq ($(strip $(KEYMAP_SECTION_ENABLE)), yes)
     endif
 endif
 
+ifeq ($(MASTER),right)  
+        OPT_DEFS += -DMASTER_IS_ON_RIGHT
+else 
+        ifneq ($(MASTER),left)
+$(error MASTER does not have a valid value(left/right))
+        endif
+endif
+
+
 # Version string
 OPT_DEFS += -DVERSION=$(shell (git describe --always --dirty || echo 'unknown') 2> /dev/null)