linux-kernel - Re: [PATCH] cpufreq / CPPC: Mark acpi

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Date:   Tue, 2 Oct 2018 15:40:19 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Nathan Chancellor <natechancellor@...il.com>
Cc:     rjw@...ysocki.net, Viresh Kumar <viresh.kumar@...aro.org>,
        linux-pm@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] cpufreq / CPPC: Mark acpi_ids as used

On Tue, Oct 2, 2018 at 3:35 PM Nathan Chancellor
<natechancellor@...il.com> wrote:
>
> Clang warns:
>
> drivers/cpufreq/cppc_cpufreq.c:431:36: warning: variable 'cppc_acpi_ids'
> is not needed and will not be emitted [-Wunneeded-internal-declaration]
> static const struct acpi_device_id cppc_acpi_ids[] = {
>                                    ^
> 1 warning generated.
>
> Mark the definition as used so that Clang understands we don't want this
> warning while not inhibiting Clang's dead code elimination from removing
> the unreferenced internal symbol when moving the data it contains to the
> globally available symbol via MODULE_DEVICE_TABLE.
>
> $ nm -S drivers/cpufreq/cppc_cpufreq.o | grep acpi | tail -1
> 0000000000000000 0000000000000040 R __mod_acpi__cppc_acpi_ids_device_table
>
> Suggested-by: Nick Desaulniers <ndesaulniers@...gle.com>
> Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>
> Signed-off-by: Nathan Chancellor <natechancellor@...il.com>
> ---
>  drivers/cpufreq/cppc_cpufreq.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c
> index 30f302149730..fd25c21cee72 100644
> --- a/drivers/cpufreq/cppc_cpufreq.c
> +++ b/drivers/cpufreq/cppc_cpufreq.c
> @@ -428,7 +428,7 @@ MODULE_LICENSE("GPL");
>
>  late_initcall(cppc_cpufreq_init);
>
> -static const struct acpi_device_id cppc_acpi_ids[] = {
> +static const struct acpi_device_id cppc_acpi_ids[] __used = {
>         {ACPI_PROCESSOR_DEVICE_HID, },
>         {}
>  };
> --
> 2.19.0
>

LGTM, thanks Nathan.  For other reviewers,
https://lkml.org/lkml/2018/9/27/91 might provide more insight into why
this is the correct fix for this particular bug.
-- 
Thanks,
~Nick Desaulniers