rename kernel_module to kernel_modules, start README mass factorings

packages/kernel_modules/user/Makefile

@@ -0,0 +1,43 @@
+.PHONY: all clean
+
+CFLAGS_EXTRA = -fopenmp -std=c99
+CXXFLAGS_EXTRA = -std=c++17
+CCFLAGS_EXTRA = -Wall -Werror -Wextra
+IN_EXT_C = .c
+IN_EXT_CXX = .cpp
+LIBS =
+OUT_EXT = .out
+
+OUTS := $(foreach IN_EXT,$(IN_EXT_C) $(IN_EXT_CXX),$(addsuffix $(OUT_EXT), $(basename $(wildcard *$(IN_EXT)))))
+ifeq ($(BR2_PACKAGE_EIGEN),y)
+	CXXFLAGS_EXTRA += -I$(STAGING_DIR)/usr/include/eigen3
+	# TODO: was failing with:
+	# fatal error: Eigen/Dense: No such file or directory as of
+	# 975ce0723ee3fa1fea1766e6683e2f3acb8558d6
+	# http://lists.busybox.net/pipermail/buildroot/2018-June/222914.html
+	#CXXFLAGS_EXTRA += $(shell $(PKG_CONFIG) --cflags eigen3)
+else
+	OUTS := $(filter-out eigen_%$(OUT_EXT),$(OUTS))
+endif
+ifeq ($(BR2_PACKAGE_LIBDRM),y)
+	LIBS += $(shell $(PKG_CONFIG) --libs libdrm)
+	CFLAGS_EXTRA += $(shell $(PKG_CONFIG) --cflags libdrm)
+else
+	OUTS := $(filter-out libdrm_%$(OUT_EXT),$(OUTS))
+endif
+ifeq ($(BR2_PACKAGE_OPENBLAS),y)
+	LIBS += -lopenblas
+else
+	OUTS := $(filter-out openblas$(OUT_EXT),$(OUTS))
+endif
+
+all: $(OUTS)
+
+%$(OUT_EXT): %$(IN_EXT_C)
+	$(CC) $(CFLAGS) $(CFLAGS_EXTRA) -o '$@' '$<' $(LIBS)
+
+%$(OUT_EXT): %$(IN_EXT_CXX)
+	$(CXX) $(CXXFLAGS) $(CXXFLAGS_EXTRA) -o '$@' '$<' $(LIBS)
+
+clean:
+	rm -f *'$(OUT_EXT)'