USED_PRNG_IMPLEMENTATIONS := $(filter prng_%,$(USEMODULE))

# Check that prng_shaxprng is not used by itself
ifneq (,$(filter prng_shaxprng,$(USEMODULE)))
  ifeq (,$(filter prng_sha1prng prng_sha256prng,$(USEMODULE)))
    $(error prng_shaxprng should not be used directly. Select one of: prng_sha1prng, prng_sha256prng)
  endif
endif

# Check that only one implementation of PRNG is used
# NOTE: prng_shaxprng is filtered out because it is used by the specific implementations
ifneq (1,$(words $(filter-out prng_shaxprng,$(USED_PRNG_IMPLEMENTATIONS))))
  $(info Currently the following prng modules are used: $(USED_PRNG_IMPLEMENTATIONS))
  $(error Only one implementation of PRNG should be used.)
endif