On Mon, 05 Oct 2020, Michael Brunner wrote:
> On Fri, 2020-10-02 at 08:01 +0100, Lee Jones wrote:
> > On Thu, 01 Oct 2020, Michael Brunner wrote:
> >
> > > The Intel 0-DAY CI Kernel Test Service reports an unused variable
> > > warning when compiling with clang for PowerPC:
> > >
> > > > > drivers/mfd/kempld-core.c:556:36: warning: unused variable
> > > > > 'kempld_acpi_table' [-Wunused-const-variable]
> > > static const struct acpi_device_id kempld_acpi_table[] = {
> > >
> > > The issue can be fixed by marking kempld_acpi_table as
> > > __maybe_unused.
> > >
> > > Fixes: e8299c7313af ("[PATCH] mfd: Add ACPI support to Kontron PLD
> > > driver")
> > >
> > > Reported-by: kernel test robot <l...@intel.com>
> > > Signed-off-by: Michael Brunner <michael.brun...@kontron.com>
> > > ---
> > > drivers/mfd/kempld-core.c | 2 +-
> > > 1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/mfd/kempld-core.c b/drivers/mfd/kempld-core.c
> > > index 1dfe556df038..273481dfaad4 100644
> > > --- a/drivers/mfd/kempld-core.c
> > > +++ b/drivers/mfd/kempld-core.c
> > > @@ -553,7 +553,7 @@ static int kempld_remove(struct platform_device
> > > *pdev)
> > > return 0;
> > > }
> > >
> > > -static const struct acpi_device_id kempld_acpi_table[] = {
> > > +static const struct acpi_device_id __maybe_unused
> > > kempld_acpi_table[] = {
> > > { "KEM0001", (kernel_ulong_t)&kempld_platform_data_generic },
> > > {}
> > > };
> >
> > This is not the right fix. Better just to compile it out completely
> > in these circumstances. I already have a fix for this in soak.
>
> Ok - thank you for the other fix you submitted!
>
> But just out of curiosity - in process/coding-style.rst is written that
> __maybe_unused should be preferred over wrapping in preprocessor
> conditionals, if a function or variable may potentially go unused in a
> particular configuration. So why is my patch not the right one here? At
> least in my tests it seemed to solve the issue.
It's a bone of contention for sure. In these kinds of scenarios
(i.e. ACPI and OF tables) it is way more common to wrap them:
$ git grep -B3 'acpi_device_id\|of_device_id' | grep 'CONFIG_ACPI\|CONFIG_OF' |
wc -l
596
$ git grep -B3 'acpi_device_id\|of_device_id' | grep __maybe_unused | wc -l
63
Parsing them out completely, also has the benefit of saving space,
reducing the size of the finalised binary.
--
Lee Jones [李琼斯]
Senior Technical Lead - Developer Services
Linaro.org │ Open source software for Arm SoCs
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