Re: [PATCH 08/13] cpufreq: acpi-cpufreq: Take 'dummy' principle one stage further

Rafael J. Wysocki
2020-07-14T16:05:13Z

On Tue, Jul 14, 2020 at 4:51 PM Lee Jones <lee.jones@linaro.org> wrote:
>
> If we fail to use a variable, even a 'dummy' one, then the compiler
> complains that it is set but not used. We know this is fine, so we
> set it to its own value here.

Which is kind of ugly in my personal view. I hope that the compiler
will actually optimize the extra code away ...

> Fixes the following W=1 kernel build warning(s):

Well, "Makes the following ... warning(s) go away:" rather ...

> drivers/cpufreq/acpi-cpufreq.c: In function ‘cpu_freq_read_intel’:
> drivers/cpufreq/acpi-cpufreq.c:247:11: warning: variable ‘dummy’ set but not used [-Wunused-but-set-variable]
> drivers/cpufreq/acpi-cpufreq.c: In function ‘cpu_freq_read_amd’:
> drivers/cpufreq/acpi-cpufreq.c:265:11: warning: variable ‘dummy’ set but not used [-Wunused-but-set-variable]
>
> Cc: Andy Grover <andrew.grover@intel.com>
> Cc: Paul Diefenbaugh <paul.s.diefenbaugh@intel.com>
> Cc: Dominik Brodowski <linux@brodo.de>
> Cc: Denis Sadykov <denis.m.sadykov@intel.com>
> Signed-off-by: Lee Jones <lee.jones@linaro.org>
> ---
> drivers/cpufreq/acpi-cpufreq.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/drivers/cpufreq/acpi-cpufreq.c b/drivers/cpufreq/acpi-cpufreq.c
> index 429e5a36c08a9..d38a693b48e03 100644
> --- a/drivers/cpufreq/acpi-cpufreq.c
> +++ b/drivers/cpufreq/acpi-cpufreq.c
> @@ -247,6 +247,7 @@ static u32 cpu_freq_read_intel(struct acpi_pct_register *not_used)
> u32 val, dummy;
>
> rdmsr(MSR_IA32_PERF_CTL, val, dummy);
> + dummy &= dummy; /* Silence set but not used warning */
> return val;
> }
>
> @@ -264,6 +265,7 @@ static u32 cpu_freq_read_amd(struct acpi_pct_register *not_used)
> u32 val, dummy;
>
> rdmsr(MSR_AMD_PERF_CTL, val, dummy);
> + dummy &= dummy; /* Silence set but not used warning */
> return val;
> }
>
> --
> 2.25.1