diff --git a/common.mk b/common.mk
new file mode 100644
index 0000000..6230c9d
--- /dev/null
+++ b/common.mk
@@ -0,0 +1,7 @@
+# Included by all module and cli Makefiles.
+# Each including Makefile must set ROOT before including this file:
+#   ROOT := $(abspath <relative path to repo root>)
+
+CC     = gcc
+CFLAGS = -std=c11 -Wall -Wextra -D_GNU_SOURCE -flto -I$(ROOT)/include
+BUILD  = $(ROOT)/build
diff --git a/dev/cli/Makefile b/dev/cli/Makefile
index 5d74e5e..ad25b27 100644
--- a/dev/cli/Makefile
+++ b/dev/cli/Makefile
@@ -1,29 +1,28 @@
-ROOT   := $(abspath ../..)
-CC      = gcc
-CFLAGS  = -std=c11 -Wall -Wextra -D_GNU_SOURCE -flto -I$(ROOT)/include
-BUILD   = $(ROOT)/build
+ROOT := $(abspath ../..)
+include $(ROOT)/common.mk
 
+CLI_BUILD      = $(BUILD)/cli
 COMMON_OBJ     = $(BUILD)/common/error.o
 MEDIA_CTRL_OBJ = $(BUILD)/media_ctrl/media_ctrl.o
 V4L2_CTRL_OBJ  = $(BUILD)/v4l2_ctrl/v4l2_ctrl.o
 
 .PHONY: all clean modules
 
-all: modules $(BUILD)/cli/media_ctrl_cli $(BUILD)/cli/v4l2_ctrl_cli
+all: modules $(CLI_BUILD)/media_ctrl_cli $(CLI_BUILD)/v4l2_ctrl_cli
 
 modules:
 	$(MAKE) -C $(ROOT)/src/modules/common
 	$(MAKE) -C $(ROOT)/src/modules/media_ctrl
 	$(MAKE) -C $(ROOT)/src/modules/v4l2_ctrl
 
-$(BUILD)/cli/media_ctrl_cli: media_ctrl_cli.c $(COMMON_OBJ) $(MEDIA_CTRL_OBJ) | $(BUILD)/cli
+$(CLI_BUILD)/media_ctrl_cli: media_ctrl_cli.c $(COMMON_OBJ) $(MEDIA_CTRL_OBJ) | $(CLI_BUILD)
 	$(CC) $(CFLAGS) -o $@ $^
 
-$(BUILD)/cli/v4l2_ctrl_cli: v4l2_ctrl_cli.c $(COMMON_OBJ) $(V4L2_CTRL_OBJ) | $(BUILD)/cli
+$(CLI_BUILD)/v4l2_ctrl_cli: v4l2_ctrl_cli.c $(COMMON_OBJ) $(V4L2_CTRL_OBJ) | $(CLI_BUILD)
 	$(CC) $(CFLAGS) -o $@ $^
 
-$(BUILD)/cli:
+$(CLI_BUILD):
 	mkdir -p $@
 
 clean:
-	rm -f $(BUILD)/cli/media_ctrl_cli $(BUILD)/cli/v4l2_ctrl_cli
+	rm -f $(CLI_BUILD)/media_ctrl_cli $(CLI_BUILD)/v4l2_ctrl_cli
diff --git a/src/modules/common/Makefile b/src/modules/common/Makefile
index d2c5ab0..a44b75d 100644
--- a/src/modules/common/Makefile
+++ b/src/modules/common/Makefile
@@ -1,17 +1,17 @@
-ROOT   := $(abspath ../../..)
-CC      = gcc
-CFLAGS  = -std=c11 -Wall -Wextra -D_GNU_SOURCE -flto -I$(ROOT)/include
-BUILD   = $(ROOT)/build/common
+ROOT := $(abspath ../../..)
+include $(ROOT)/common.mk
+
+MODULE_BUILD = $(BUILD)/common
 
 .PHONY: all clean
 
-all: $(BUILD)/error.o
+all: $(MODULE_BUILD)/error.o
 
-$(BUILD)/error.o: error.c $(ROOT)/include/error.h | $(BUILD)
+$(MODULE_BUILD)/error.o: error.c $(ROOT)/include/error.h | $(MODULE_BUILD)
 	$(CC) $(CFLAGS) -c -o $@ $<
 
-$(BUILD):
+$(MODULE_BUILD):
 	mkdir -p $@
 
 clean:
-	rm -f $(BUILD)/error.o
+	rm -f $(MODULE_BUILD)/error.o
diff --git a/src/modules/media_ctrl/Makefile b/src/modules/media_ctrl/Makefile
index 91aca5c..8269ac9 100644
--- a/src/modules/media_ctrl/Makefile
+++ b/src/modules/media_ctrl/Makefile
@@ -1,17 +1,17 @@
-ROOT   := $(abspath ../../..)
-CC      = gcc
-CFLAGS  = -std=c11 -Wall -Wextra -D_GNU_SOURCE -flto -I$(ROOT)/include
-BUILD   = $(ROOT)/build/media_ctrl
+ROOT := $(abspath ../../..)
+include $(ROOT)/common.mk
+
+MODULE_BUILD = $(BUILD)/media_ctrl
 
 .PHONY: all clean
 
-all: $(BUILD)/media_ctrl.o
+all: $(MODULE_BUILD)/media_ctrl.o
 
-$(BUILD)/media_ctrl.o: media_ctrl.c $(ROOT)/include/media_ctrl.h $(ROOT)/include/error.h | $(BUILD)
+$(MODULE_BUILD)/media_ctrl.o: media_ctrl.c $(ROOT)/include/media_ctrl.h $(ROOT)/include/error.h | $(MODULE_BUILD)
 	$(CC) $(CFLAGS) -c -o $@ $<
 
-$(BUILD):
+$(MODULE_BUILD):
 	mkdir -p $@
 
 clean:
-	rm -f $(BUILD)/media_ctrl.o
+	rm -f $(MODULE_BUILD)/media_ctrl.o
diff --git a/src/modules/v4l2_ctrl/Makefile b/src/modules/v4l2_ctrl/Makefile
index 07150bb..7b31550 100644
--- a/src/modules/v4l2_ctrl/Makefile
+++ b/src/modules/v4l2_ctrl/Makefile
@@ -1,17 +1,17 @@
-ROOT   := $(abspath ../../..)
-CC      = gcc
-CFLAGS  = -std=c11 -Wall -Wextra -D_GNU_SOURCE -flto -I$(ROOT)/include
-BUILD   = $(ROOT)/build/v4l2_ctrl
+ROOT := $(abspath ../../..)
+include $(ROOT)/common.mk
+
+MODULE_BUILD = $(BUILD)/v4l2_ctrl
 
 .PHONY: all clean
 
-all: $(BUILD)/v4l2_ctrl.o
+all: $(MODULE_BUILD)/v4l2_ctrl.o
 
-$(BUILD)/v4l2_ctrl.o: v4l2_ctrl.c $(ROOT)/include/v4l2_ctrl.h $(ROOT)/include/error.h | $(BUILD)
+$(MODULE_BUILD)/v4l2_ctrl.o: v4l2_ctrl.c $(ROOT)/include/v4l2_ctrl.h $(ROOT)/include/error.h | $(MODULE_BUILD)
 	$(CC) $(CFLAGS) -c -o $@ $<
 
-$(BUILD):
+$(MODULE_BUILD):
 	mkdir -p $@
 
 clean:
-	rm -f $(BUILD)/v4l2_ctrl.o
+	rm -f $(MODULE_BUILD)/v4l2_ctrl.o