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Date: Tue, 14 Jul 2020 17:20:54 +0100 From: Robin Murphy <robin.murphy@....com> To: "Rafael J. Wysocki" <rafael@...nel.org>, Lee Jones <lee.jones@...aro.org> Cc: Denis Sadykov <denis.m.sadykov@...el.com>, Andy Grover <andrew.grover@...el.com>, Linux PM <linux-pm@...r.kernel.org>, Viresh Kumar <viresh.kumar@...aro.org>, "Rafael J. Wysocki" <rjw@...ysocki.net>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, Paul Diefenbaugh <paul.s.diefenbaugh@...el.com>, Linux ARM <linux-arm-kernel@...ts.infradead.org>, Dominik Brodowski <linux@...do.de> Subject: Re: [PATCH 08/13] cpufreq: acpi-cpufreq: Take 'dummy' principle one stage further On 2020-07-14 17:03, Rafael J. Wysocki wrote: > On Tue, Jul 14, 2020 at 4:51 PM Lee Jones <lee.jones@...aro.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 ... Isn't that what we have __maybe_unused and __always_unused for? Robin. >> 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@...el.com> >> Cc: Paul Diefenbaugh <paul.s.diefenbaugh@...el.com> >> Cc: Dominik Brodowski <linux@...do.de> >> Cc: Denis Sadykov <denis.m.sadykov@...el.com> >> Signed-off-by: Lee Jones <lee.jones@...aro.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 >> > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@...ts.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel >
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