Re: [PATCH] kbuild: add more hints about SUBDIRS replacement

[Sam Ravnborg <sam@ravnborg.org>]

On Tue, Jun 25, 2019 at 05:51:27PM +0900, Masahiro Yamada wrote:
> Commit 0126be38d988 ("kbuild: announce removal of SUBDIRS if used")
> added a hint about the 'SUBDIRS' replacement, but it was not clear
> enough.
> 
> Multiple people sent me similar questions, patches.
> 
>   https://lkml.org/lkml/2019/1/17/456
> 
> I did not mean to suggest M= for building a subdirectory in the kernel
> tree.
> 
> >From the commit 669efc76b317 ("net: hns3: fix compile error"), people
> already (ab)use M=... to do that because it seems to work to some extent.
> 
> Documentation/kbuild/kbuild.txt says M= and KBUILD_EXTMOD are used for
> building external modules.
> 
> In fact, Kbuild supports the single target '%/' for this purpose, but
> this may not be noticed much.
> 
> Kindly add more hints.
> 
> Makefile:213: ================= WARNING ================
> Makefile:214: 'SUBDIRS' will be removed after Linux 5.3
> Makefile:215:
> Makefile:216: If you are building an individual subdirectory
> Makefile:217: in the kernel tree, you can do like this:
> Makefile:218: $ make path/to/dir/you/want/to/build/
> Makefile:219: (Do not forget the trailing slash)
> Makefile:220:
> Makefile:221: If you are building an external module,
> Makefile:222: Please use 'M=' or 'KBUILD_EXTMOD' instead
> Makefile:223: ==========================================
> 
> Suggested-by: Christoph Hellwig <hch@lst.de>
> Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

Nice!

Acked-by: Sam Ravnborg <sam@ravnborg.org>

	Sam