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From:   Nick Desaulniers <ndesaulniers@google.com>
Date:   Tue, 17 Nov 2020 10:33:47 -0800
Message-ID: <CAKwvOd=OsYyPYDg=CU5cHGNxYj6UKcwUKTmrweeERJLkiVwekw@mail.gmail.com>
Subject: Re: [PATCH] lib: compile memcat_p only when needed
To:     "Enrico Weigelt, metux IT consult" <info@metux.net>,
        Andrew Morton <akpm@linux-foundation.org>,
        Masahiro Yamada <masahiroy@kernel.org>
Cc:     LKML <linux-kernel@vger.kernel.org>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Maxime Coquelin <mcoquelin.stm32@gmail.com>,
        Alexandre Torgue <alexandre.torgue@st.com>,
        Martin KaFai Lau <kafai@fb.com>,
        Song Liu <songliubraving@fb.com>, Yonghong Song <yhs@fb.com>,
        Andrii Nakryiko <andrii@kernel.org>,
        John Fastabend <john.fastabend@gmail.com>,
        KP Singh <kpsingh@chromium.org>,
        Network Development <netdev@vger.kernel.org>,
        bpf <bpf@vger.kernel.org>,
        clang-built-linux <clang-built-linux@googlegroups.com>
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On Tue, Nov 17, 2020 at 9:38 AM Enrico Weigelt, metux IT consult
<info@metux.net> wrote:
>
> The library function memcat_p() is currently used only once.
> (drivers/hwtracing/stm). So, often completely unused.

Any harm in just moving the definition into drivers/hwtracing/stm?
Then we don't need any Kconfig additions.  There never were many users
of this function, and there probably never will be.

>
> Reducing the kernel size by about 4k by compiling it
> conditionally, only when needed.
>
> Signed-off-by: Enrico Weigelt, metux IT consult <info@metux.net>
> ---
>  drivers/hwtracing/stm/Kconfig | 1 +
>  lib/Kconfig                   | 3 +++
>  lib/Kconfig.debug             | 1 +
>  lib/Makefile                  | 4 +++-
>  4 files changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/hwtracing/stm/Kconfig b/drivers/hwtracing/stm/Kconfig
> index aad594fe79cc..8ce5cfd759d1 100644
> --- a/drivers/hwtracing/stm/Kconfig
> +++ b/drivers/hwtracing/stm/Kconfig
> @@ -3,6 +3,7 @@ config STM
>         tristate "System Trace Module devices"
>         select CONFIGFS_FS
>         select SRCU
> +       select GENERIC_LIB_MEMCAT_P
>         help
>           A System Trace Module (STM) is a device exporting data in System
>           Trace Protocol (STP) format as defined by MIPI STP standards.
> diff --git a/lib/Kconfig b/lib/Kconfig
> index b46a9fd122c8..b42ed8d68937 100644
> --- a/lib/Kconfig
> +++ b/lib/Kconfig
> @@ -686,6 +686,9 @@ config GENERIC_LIB_CMPDI2
>  config GENERIC_LIB_UCMPDI2
>         bool
>
> +config GENERIC_LIB_MEMCAT_P
> +       tristate
> +
>  config PLDMFW
>         bool
>         default n
> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> index c789b39ed527..beb5adb2f0b7 100644
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -2334,6 +2334,7 @@ config TEST_DEBUG_VIRTUAL
>
>  config TEST_MEMCAT_P
>         tristate "Test memcat_p() helper function"
> +       select GENERIC_LIB_MEMCAT_P
>         help
>           Test the memcat_p() helper for correctly merging two
>           pointer arrays together.
> diff --git a/lib/Makefile b/lib/Makefile
> index ce45af50983a..18fd6630be0b 100644
> --- a/lib/Makefile
> +++ b/lib/Makefile
> @@ -36,7 +36,9 @@ lib-y := ctype.o string.o vsprintf.o cmdline.o \
>          flex_proportions.o ratelimit.o show_mem.o \
>          is_single_threaded.o plist.o decompress.o kobject_uevent.o \
>          earlycpio.o seq_buf.o siphash.o dec_and_lock.o \
> -        nmi_backtrace.o nodemask.o win_minmax.o memcat_p.o
> +        nmi_backtrace.o nodemask.o win_minmax.o
> +
> +obj-$(CONFIG_GENERIC_LIB_MEMCAT_P) += memcat_p.o
>
>  lib-$(CONFIG_PRINTK) += dump_stack.o
>  lib-$(CONFIG_SMP) += cpumask.o
> --
> 2.11.0
>
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-- 
Thanks,
~Nick Desaulniers