linux-kernel - Re: drivers/pinctrl/intel/pinctrl-intel.c:1663:14: warning: variable 'dummy' set but not used

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Message-ID: <YIkgNWRJ+9BpEtvb@smile.fi.intel.com>
Date:   Wed, 28 Apr 2021 11:43:33 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     kernel test robot <lkp@...el.com>, Arnd Bergmann <arnd@...db.de>,
        Nick Desaulniers <ndesaulniers@...gle.com>
Cc:     kbuild-all@...ts.01.org, clang-built-linux@...glegroups.com,
        linux-kernel@...r.kernel.org
Subject: Re: drivers/pinctrl/intel/pinctrl-intel.c:1663:14: warning: variable
 'dummy' set but not used

+Cc: Arnd and Nick

(Seems like a clang bug)

On Wed, Apr 28, 2021 at 08:10:34AM +0800, kernel test robot wrote:
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> head:   e359bce39d9085ab24eaa0bb0778bb5f6894144a
> commit: 10c857f063fc63902160755a6e23fa594290c6d3 pinctrl: cherryview: Switch to use intel_pinctrl_get_soc_data()
> date:   8 months ago
> config: x86_64-randconfig-a005-20210426 (attached as .config)
> compiler: clang version 13.0.0 (https://github.com/llvm/llvm-project 87fc97169e7901dfe56ca0da0d92da0c02d2ef48)
> reproduce (this is a W=1 build):
>         wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
>         chmod +x ~/bin/make.cross
>         # install x86_64 cross compiling tool for clang build
>         # apt-get install binutils-x86-64-linux-gnu
>         # https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=10c857f063fc63902160755a6e23fa594290c6d3
>         git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
>         git fetch --no-tags linus master
>         git checkout 10c857f063fc63902160755a6e23fa594290c6d3
>         # save the attached .config to linux build tree
>         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 ARCH=x86_64 
> 
> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kernel test robot <lkp@...el.com>
> 
> All warnings (new ones prefixed by >>):
> 
> >> drivers/pinctrl/intel/pinctrl-intel.c:1663:14: warning: variable 'dummy' set but not used [-Wunused-but-set-variable]
>            const char *dummy;
>                        ^
>    1 warning generated.

Seems to me a bug in clang. The variable is used to check if the body of the
loop should be executed or not.

> vim +/dummy +1663 drivers/pinctrl/intel/pinctrl-intel.c
> 
> a0a5f7661e1c49 Chris Chiu      2019-04-15  1656  
> 7101e022523bfb Andy Shevchenko 2019-10-22  1657  static void intel_restore_hostown(struct intel_pinctrl *pctrl, unsigned int c,
> 7101e022523bfb Andy Shevchenko 2019-10-22  1658  				  void __iomem *base, unsigned int gpp, u32 saved)
> 7101e022523bfb Andy Shevchenko 2019-10-22  1659  {
> 7101e022523bfb Andy Shevchenko 2019-10-22  1660  	const struct intel_community *community = &pctrl->communities[c];
> 7101e022523bfb Andy Shevchenko 2019-10-22  1661  	const struct intel_padgroup *padgrp = &community->gpps[gpp];
> 7101e022523bfb Andy Shevchenko 2019-10-22  1662  	struct device *dev = pctrl->dev;
> d1bfd0229ec4de Andy Shevchenko 2020-06-10 @1663  	const char *dummy;
> d1bfd0229ec4de Andy Shevchenko 2020-06-10  1664  	u32 requested = 0;
> d1bfd0229ec4de Andy Shevchenko 2020-06-10  1665  	unsigned int i;
> 7101e022523bfb Andy Shevchenko 2019-10-22  1666  
> e5a4ab6a55e230 Andy Shevchenko 2020-04-13  1667  	if (padgrp->gpio_base == INTEL_GPIO_BASE_NOMAP)
> 7101e022523bfb Andy Shevchenko 2019-10-22  1668  		return;
> 7101e022523bfb Andy Shevchenko 2019-10-22  1669  
> d1bfd0229ec4de Andy Shevchenko 2020-06-10  1670  	for_each_requested_gpio_in_range(&pctrl->chip, i, padgrp->gpio_base, padgrp->size, dummy)
> d1bfd0229ec4de Andy Shevchenko 2020-06-10  1671  		requested |= BIT(i);
> d1bfd0229ec4de Andy Shevchenko 2020-06-10  1672  
> 942c5ea49ffbe2 Andy Shevchenko 2019-10-22  1673  	if (!intel_gpio_update_reg(base + gpp * 4, requested, saved))
> 7101e022523bfb Andy Shevchenko 2019-10-22  1674  		return;
> 7101e022523bfb Andy Shevchenko 2019-10-22  1675  
> 764cfe33517f7c Andy Shevchenko 2019-10-22  1676  	dev_dbg(dev, "restored hostown %u/%u %#08x\n", c, gpp, readl(base + gpp * 4));
> 7101e022523bfb Andy Shevchenko 2019-10-22  1677  }
> 7101e022523bfb Andy Shevchenko 2019-10-22  1678  
> 
> :::::: The code at line 1663 was first introduced by commit
> :::::: d1bfd0229ec4deb53e61f95c050b524152fd0d9e pinctrl: intel: Make use of for_each_requested_gpio_in_range()
> 
> :::::: TO: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> :::::: CC: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> 
> ---
> 0-DAY CI Kernel Test Service, Intel Corporation
> https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org



-- 
With Best Regards,
Andy Shevchenko