Enabling CONFIG options often requires additional features, like target compiler capabilities, host tools, etc. As for the target compiler capabilities, Kconfig is able to add proper dependencies. For example, config STACKPROTECTOR ... depends on $(cc-option,-fstack-protector) The CONFIG option is simply disabled if unsupported by the compiler. This seems sensible since otherwise, there is no way to avoid the build error. In the discussion [1], doing similar for host tools was unacceptable. Build errors caused by missing host tools are easy to fix; just install them to your build machine. So, let the build fail instead of disabling CONFIG options silently. We already have such checks in random places in makefiles. What I do not like is that people tend to do that in the top Makefile. The top Makefile is too cluttered, and what is worse, $(error ...) functions in the top Makefile could be false positive. (Please note the top Makefile includes the stale include/config/auto.conf before syncconfig updates it.) This adds a new file scripts/Makefile.toolcheck to check additional tools depending on the kernel configuration. This check is run immediately after syncconfig, i.e., when a user attempts to build something with a new set of CONFIG options. [1] https://patchwork.kernel.org/patch/10516049/ Signed-off-by: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx> --- Makefile | 1 + scripts/Makefile.toolcheck | 35 +++++++++++++++++++++++++++++++++++ 2 files changed, 36 insertions(+) create mode 100644 scripts/Makefile.toolcheck diff --git a/Makefile b/Makefile index bf3786e..23a204a 100644 --- a/Makefile +++ b/Makefile @@ -633,6 +633,7 @@ $(KCONFIG_CONFIG) include/config/auto.conf.cmd: ; # include/config/auto.conf (which mirrors .config). include/config/%.conf: $(KCONFIG_CONFIG) include/config/auto.conf.cmd $(Q)$(MAKE) -f $(srctree)/Makefile syncconfig + $(Q)$(MAKE) -f $(srctree)/scripts/Makefile.toolcheck else # External modules and some install targets need include/generated/autoconf.h # and include/config/auto.conf but do not care if they are up-to-date. diff --git a/scripts/Makefile.toolcheck b/scripts/Makefile.toolcheck new file mode 100644 index 0000000..f3c165d --- /dev/null +++ b/scripts/Makefile.toolcheck @@ -0,0 +1,35 @@ +# SPDX-License-Identifier: GPL-2.0 +# =========================================================================== +# Host tools check +# =========================================================================== +# +# Some additional tools might be required depending on the kernel configuration. +# Check if they are installed on the host machine, and if missing, error out +# with a user-friendly message. + +include include/config/auto.conf + +__toolcheck: + @: + +PHONY += $(toolcheck-y) +__toolcheck: $(toolcheck-y) + +define populate_toolcheck +__toolcheck: check_$(1) +PHONY += check_$(1) +check_$(1): + $(Q){ $(chk_$(1)); } >/dev/null 2>&1 || { \ + echo "*" >&2; \ + for msg in $(msg_$(1)); \ + do \ + echo "* $$$${msg}" >&2; \ + done; \ + echo "*" >&2; \ + /bin/false; \ + } +endef + +$(foreach c, $(toolcheck-y), $(eval $(call populate_toolcheck,$(c)))) + +.PHONY: $(PHONY) -- 2.7.4