Re: [Xen-devel] [XEN PATCH v2 09/12] xen/build: include include/config/auto.conf in main Makefile

[Jan Beulich <jbeulich@xxxxxxxx>]

On 17.01.2020 11:53, Anthony PERARD wrote:
> --- a/xen/Makefile
> +++ b/xen/Makefile
> @@ -49,7 +49,71 @@ default: build
>  .PHONY: dist
>  dist: install
>  
> -build install:: include/config/auto.conf
> +
> +ifndef root-make-done
> +# section to run before calling Rules.mk, but only once.
> +#
> +# To make sure we do not include .config for any of the *config targets
> +# catch them early, and hand them over to tools/kconfig/Makefile
> +
> +clean-targets := %clean
> +no-dot-config-targets := $(clean-targets) \
> +                      uninstall debug cloc \
> +                      cscope TAGS tags MAP gtags \
> +                      xenversion
> +
> +config-build :=

Is this actually needed? While correct (afaict) together with the
ifdef further down, I find this aspect of make behavior a little
confusing, and hence it would seem slightly better if there was
no empty definition of this symbol.

> +need-config  := 1

Here and below, would it be possible to use y instead of 1, to
match how "true" gets expressed in various places elsewhere?
Or would there again be deviation-from-Linux concerns?

> +ifneq ($(filter $(no-dot-config-targets), $(MAKECMDGOALS)),)
> +     ifeq ($(filter-out $(no-dot-config-targets), $(MAKECMDGOALS)),)
> +             need-config :=
> +     endif
> +endif
> +
> +ifneq ($(filter config %config,$(MAKECMDGOALS)),)

Just $(filter %config, ...) suffices here, afaict, similar to
above "%clean" also being used to cover "clean".

> +     config-build := 1
> +endif
> +
> +export root-make-done := 1
> +endif # root-make-done
> +
> +ifdef config-build
> +# ===========================================================================
> +# *config targets only - make sure prerequisites are updated, and descend
> +# in tools/kconfig to make the *config target
> +
> +config: FORCE
> +     $(MAKE) -f $(BASEDIR)/tools/kconfig/Makefile.kconfig ARCH=$(ARCH) 
> SRCARCH=$(SRCARCH) HOSTCC="$(HOSTCC)" HOSTCXX="$(HOSTCXX)" $@
> +
> +# Config.mk tries to include .config file, don't try to remake it
> +%/.config: ;

This didn't exist before - why is it needed all of the sudden?

> +%config: FORCE
> +     $(MAKE) -f $(BASEDIR)/tools/kconfig/Makefile.kconfig ARCH=$(ARCH) 
> SRCARCH=$(SRCARCH) HOSTCC="$(HOSTCC)" HOSTCXX="$(HOSTCXX)" $@
> +
> +else # !config-build
> +
> +ifdef need-config
> +include include/config/auto.conf
> +# Read in dependencies to all Kconfig* files, make sure to run syncconfig if
> +# changes are detected.
> +include include/config/auto.conf.cmd
> +
> +# Allow people to just run `make` as before and not force them to configure
> +$(KCONFIG_CONFIG):
> +     $(MAKE) -f $(BASEDIR)/tools/kconfig/Makefile.kconfig ARCH=$(ARCH) 
> SRCARCH=$(SRCARCH) HOSTCC="$(HOSTCC)" HOSTCXX="$(HOSTCXX)" defconfig
> +
> +# The actual configuration files used during the build are stored in
> +# include/generated/ and include/config/. Update them if .config is newer 
> than
> +# include/config/auto.conf (which mirrors .config).
> +#
> +# This exploits the 'multi-target pattern rule' trick.
> +# The syncconfig should be executed only once to make all the targets.
> +%/auto.conf %/auto.conf.cmd: $(KCONFIG_CONFIG)
> +     $(MAKE) -f $(BASEDIR)/tools/kconfig/Makefile.kconfig ARCH=$(ARCH) 
> SRCARCH=$(SRCARCH) HOSTCC="$(HOSTCC)" HOSTCXX="$(HOSTCXX)" syncconfig

Previously the target pattern was include/config/%.conf. Is there a
particular reason for the switch?

Jan

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