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

[Robin Murphy]

On 2020-07-14 17:03, Rafael J. Wysocki wrote:
> On Tue, Jul 14, 2020 at 4:51 PM Lee Jones <lee.jones@xxxxxxxxxx> 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 âcpu_freq_read_intelâ:
> >   drivers/cpufreq/acpi-cpufreq.c:247:11: warning: variable âdummyâ set but not used [-Wunused-but-set-variable]
> >   drivers/cpufreq/acpi-cpufreq.c: In function âcpu_freq_read_amdâ:
> >   drivers/cpufreq/acpi-cpufreq.c:265:11: warning: variable âdummyâ set but not used [-Wunused-but-set-variable]
> >
> > Cc: Andy Grover <andrew.grover@xxxxxxxxx>
> > Cc: Paul Diefenbaugh <paul.s.diefenbaugh@xxxxxxxxx>
> > Cc: Dominik Brodowski <linux@xxxxxxxx>
> > Cc: Denis Sadykov <denis.m.sadykov@xxxxxxxxx>
> > Signed-off-by: Lee Jones <lee.jones@xxxxxxxxxx>
> > ---
> >   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
>
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