+builddir ?= build/$(patsubst $(shell cd $(top_srcdir); pwd)/%,%,$(CURDIR))
+
+C_SRC ?= $(notdir $(wildcard $(srcdir)/*.c))
+S_SRC ?= $(notdir $(wildcard $(srcdir)/*.S))
+OBJS ?= $(addprefix $(top_builddir)/$(builddir)/,$(C_SRC:%.c=%.o) $(S_SRC:%.S=%.o))