[Buildroot] [PATCH 1/9 v2] core: add the possibility to provide help for custom rules

[Thomas Petazzoni <thomas.petazzoni@free-electrons.com>]

Hello,

On Fri, 11 Mar 2016 18:41:09 +0100, Yann E. MORIN wrote:

> diff --git a/Makefile b/Makefile
> index 98c8dc7..7bb5f6d 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -966,6 +966,7 @@ endif
>  	@echo '  source-check           - check selected packages for valid download URLs'
>  	@echo '  external-deps          - list external packages used'
>  	@echo '  legal-info             - generate info about license compliance'
> +	@echo '  help-custom            - print help about custom actions (if any)'
>  	@echo
>  	@echo '  make V=0|1             - 0 => quiet build (default), 1 => verbose build'
>  	@echo '  make O=dir             - Locate all output files in "dir", including .config'
> @@ -974,6 +975,12 @@ endif
>  	@echo 'it on-line at http://buildroot.org/docs.html'
>  	@echo
>  
> +# This rule does nothing, it is expected to be overloaded by
> +# a br2-external tree or a local.mk . However, it must exist,
> +# as we reference it in the main help, above. Making the rule
> +# .PHONY does not work.
> +help-custom:
> +

There is a pretty important problem with this implementation (which
gets even worse when PATCH 2 is applied), but I am not sure why it
happens: the custom help is not taken into account if you don't have a
configuration file defined. This is weird, because BR2_EXTERNAL_FILE
gets included outside of the BR2_HAVE_DOT_CONFIG condition. But still:

thomas at skate:~/projets/buildroot (master)$ cat /tmp/external/external.mk 
help-custom:
	@echo TEST
thomas at skate:~/projets/buildroot (master)$ make BR2_EXTERNAL=/tmp/external help-custom
make[1]: Nothing to be done for 'help-custom'.

And then, if I create a .config file:

thomas at skate:~/projets/buildroot (master)$ make defconfig
[...]
thomas at skate:~/projets/buildroot (master)$ make BR2_EXTERNAL=/tmp/external help-custom
TEST

This is not expected, since the help text is supposed to be available
even when no configuration has been defined.

Thomas
-- 
Thomas Petazzoni, CTO, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com