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Wysocki" , Denis Sadykov , Andy Grover , Linux PM , Viresh Kumar , "Rafael J. Wysocki" , Linux Kernel Mailing List , Paul Diefenbaugh , Linux ARM , Dominik Brodowski Subject: Re: [PATCH 08/13] cpufreq: acpi-cpufreq: Take 'dummy' principle one stage further Message-ID: <20200714210056.GF1398296@dell> References: <20200714145049.2496163-1-lee.jones@linaro.org> <20200714145049.2496163-9-lee.jones@linaro.org> <8b2f7674-9e33-e09c-cf99-84c59edb9779@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <8b2f7674-9e33-e09c-cf99-84c59edb9779@arm.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 14 Jul 2020, Robin Murphy wrote: > On 2020-07-14 17:03, Rafael J. Wysocki wrote: > > On Tue, Jul 14, 2020 at 4:51 PM Lee Jones 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 ... > > Isn't that what we have __maybe_unused and __always_unused for? Yes, that would be better. I didn't know you could do that with standard variables. Will fix. > > > 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 > > > Cc: Paul Diefenbaugh > > > Cc: Dominik Brodowski > > > Cc: Denis Sadykov > > > Signed-off-by: Lee Jones > > > --- > > > 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; > > > } > > > > > > > _______________________________________________ > > linux-arm-kernel mailing list > > linux-arm-kernel@lists.infradead.org > > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel > > -- Lee Jones [李琼斯] Senior Technical Lead - Developer Services Linaro.org │ Open source software for Arm SoCs Follow Linaro: Facebook | Twitter | Blog