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From:   Masahiro Yamada <masahiroy@kernel.org>
Date:   Wed, 27 Jan 2021 02:59:44 +0900
Message-ID: <CAK7LNARLiLzqpMfmvVMJ8pT7-wYjfrP54mey_MCMbULLFY_H+A@mail.gmail.com>
Subject: Re: [RFC 0/2] Kbuild: Support nested composite objects
To:     Elliot Berman <eberman@codeaurora.org>
Cc:     Nick Desaulniers <ndesaulniers@google.com>,
        Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Michal Marek <michal.lkml@markovi.net>,
        Sami Tolvanen <samitolvanen@google.com>,
        Trilok Soni <tsoni@codeaurora.org>,
        Mahesh Kumar Kalikot Veetil <mkalikot@codeaurora.org>,
        Jeff Johnson <jjohnson@codeaurora.org>
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On Sat, Jan 23, 2021 at 4:27 AM Elliot Berman <eberman@codeaurora.org> wrote:
>
> This series was developed after discussion in https://lkml.org/lkml/2021/1/19/850
>
> The motivation for this series is an out-of-tree module which contains a large
> number of source files. This causes Kbuild to exceed the maximum command line
> argument length when linking the files. Proposal here permits composite objects
> to contain other composite objects. This allows the driver to split linking into
> several steps and avoid the maximum command line length error.


External modules often get the cold shoulder.

For example,
https://lore.kernel.org/patchwork/patch/1175556/#1372233


This problem has not been observed in the upstream tree.

I do not see a good reason to complicate the build
infrastructure for some external modules.


> Kbuild composite objects only supports one level of composite objects.
> That is, a composite object may only be composed of real compilable
> source files.
>
> As a simple example, the following Kbuild description is now supported:
>
> bar-a-y := a/bar0.o a/bar1.o
> bar-b-y := b/bar2.o b/bar3.o
>
> foo-objs := bar-a.o bar-b.o
>
> obj-m += foo.o
>
> Add such support by recursively searching for composite objects and
> listing them in $(multi-used-*) and $(real-obj-*).
>
> Elliot Berman (2):
>   Kbuild: Make composite object searching more generic
>   Kbuild: Support nested composite objects
>
>  scripts/Makefile.lib | 20 ++++++++++++++++----
>  1 file changed, 16 insertions(+), 4 deletions(-)
>
> --
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> a Linux Foundation Collaborative Project
>


-- 
Best Regards
Masahiro Yamada