Re: [PATCH] pinctrl: core: Fix unused variable build warnings

[Drew Fustini <drew@xxxxxxxxxxxxxxx>]

On Mon, Nov 23, 2020 at 11:51:29PM -0800, Pawan Gupta wrote:
> On Mon, Nov 23, 2020 at 09:06:18PM -0800, Drew Fustini wrote:
> > On Mon, Nov 23, 2020 at 02:33:33PM -0800, Pawan Gupta wrote:
> > > A recent commit f1b206cf7c57 ("pinctrl: core: print gpio in pins debugfs
> > > file") added build warnings when CONFIG_GPIOLIB=n. Offcourse the kernel
> > > fails to build when warnings are treated as errors. Below is the error
> > > message:
> > > 
> > >   $ make CFLAGS_KERNEL+=-Werror
> > > 
> > >   drivers/pinctrl/core.c: In function ‘pinctrl_pins_show’:
> > >   drivers/pinctrl/core.c:1607:20: error: unused variable ‘chip’ [-Werror=unused-variable]
> > >    1607 |  struct gpio_chip *chip;
> > >         |                    ^~~~
> > >   drivers/pinctrl/core.c:1606:15: error: unused variable ‘gpio_num’ [-Werror=unused-variable]
> > >    1606 |  unsigned int gpio_num;
> > >         |               ^~~~~~~~
> > >   drivers/pinctrl/core.c:1605:29: error: unused variable ‘range’ [-Werror=unused-variable]
> > >    1605 |  struct pinctrl_gpio_range *range;
> > >         |                             ^~~~~
> > >   cc1: all warnings being treated as errors
> > > 
> > > These variables are only used inside #ifdef CONFIG_GPIOLIB, fix the
> > > build warnings by wrapping the definition inside the config.
> > > 
> > > Fixes: f1b206cf7c57 ("pinctrl: core: print gpio in pins debugfs file")
> > > Signed-off-by: Pawan Gupta <writetopawan@xxxxxxxxx>
> > > ---
> > >  drivers/pinctrl/core.c | 3 ++-
> > >  1 file changed, 2 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/pinctrl/core.c b/drivers/pinctrl/core.c
> > > index 3663d87f51a0..1bb371a5cf8d 100644
> > > --- a/drivers/pinctrl/core.c
> > > +++ b/drivers/pinctrl/core.c
> > > @@ -1602,10 +1602,11 @@ static int pinctrl_pins_show(struct seq_file *s, void *what)
> > >  	struct pinctrl_dev *pctldev = s->private;
> > >  	const struct pinctrl_ops *ops = pctldev->desc->pctlops;
> > >  	unsigned i, pin;
> > > +#ifdef CONFIG_GPIOLIB
> > >  	struct pinctrl_gpio_range *range;
> > >  	unsigned int gpio_num;
> > >  	struct gpio_chip *chip;
> > > -
> > > +#endif
> > >  	seq_printf(s, "registered pins: %d\n", pctldev->desc->npins);
> > >  
> > >  	mutex_lock(&pctldev->mutex);
> > > -- 
> > > 2.21.3
> > > 
> > 
> > Thanks for pointing this out.  I don't have any systems where I build
> > without CONFIG_GPIOLIB so I missed this.
> > 
> > I'm having trouble figuring out a .config that will reproduce this.  I
> > tried tinyconfig but it compiled clean.
> 
> Just setting CONFIG_GPIOLIB=n via menuconfig is not an option?  Have you
> tried x86?

There were other options related to pinctrl both for my ARM board and my
laptop that were forcing GPIOLIB to stay on. 

> 
> > Could you share your .config?
> 
> Attaching the .config that reproduces the build warning.

Thanks.  I was able to reproduce the error with your config.

I applied your patch and it did resolve the error for me.

Reviewed-by: Drew Fustini <drew@xxxxxxxxxxxxxxx>