Re: [PATCH] Makefile: add comment to discourage tools/* addition for kernel builds

[Nicolas Schier <nicolas@fjasle.eu>]

On Wed, Jun 19, 2024 at 03:21:42PM +0900 Masahiro Yamada wrote:
> Kbuild provides scripts/Makefile.host to build host programs used for
> building the kernel. Unfortunately, there are two exceptions that opt
> out of Kbuild. The build system under tools/ is a cheesy replica, and
> is always a disaster. I was recently poked about a problem in the tools
> build issue, which I do not maintain (and nobody maintains). [1]
> 
> Without a comment, somebody might believe this is the right location
> because that is where objtool lives, even when a more robust Kbuild
> syntax satisfies their needs. [2]
> 
> [1]: https://lore.kernel.org/linux-kbuild/ZnIYWBgrJ-IJtqK8@google.com/T/#m8ece130dd0e23c6f2395ed89070161948dee8457
> [2]: https://lore.kernel.org/all/20240618200501.GA1611012@google.com/
> 
> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
> ---
> 
>  Makefile | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/Makefile b/Makefile
> index 471f2df86422..ba070596ad4e 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -1331,6 +1331,11 @@ prepare: tools/bpf/resolve_btfids
>  endif
>  endif
>  
> +# README
> +# The tools build system is not a part of Kbuild. Before adding yet another
> +# tools/* here, please consider if the standard "hostprogs" syntax satisfies
> +# your needs.
> +

Perhaps add a "See Documentation/kbuild/makefiles.rst for details." ?

I do understand the need for clarification.

Acked-by: Nicolas Schier <nicolas@fjasle.eu>