linux-kernel - Re: [jic23-iio:testing 58/58] drivers/iio/adc/mcp3911.c:274:6: warning: variable 'tmp0' set but not used

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Date:   Thu, 22 Sep 2022 11:59:25 +0100
From:   Jonathan Cameron <Jonathan.Cameron@...wei.com>
To:     kernel test robot <lkp@...el.com>
CC:     Marcus Folkesson <marcus.folkesson@...il.com>,
        <llvm@...ts.linux.dev>, <kbuild-all@...ts.01.org>,
        <linux-kernel@...r.kernel.org>,
        Andy Shevchenko <andy.shevchenko@...il.com>
Subject: Re: [jic23-iio:testing 58/58] drivers/iio/adc/mcp3911.c:274:6:
 warning: variable 'tmp0' set but not used

On Thu, 22 Sep 2022 08:50:17 +0800
kernel test robot <lkp@...el.com> wrote:

> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/jic23/iio.git testing
> head:   d4e1a549566b9ea8b96e80f0cdcbe99714ac256e
> commit: d4e1a549566b9ea8b96e80f0cdcbe99714ac256e [58/58] iio: adc: mcp3911: add support to set PGA
> config: x86_64-randconfig-a012
> compiler: clang version 14.0.6 (https://github.com/llvm/llvm-project f28c006a5895fc0e329fe15fead81e37457cb1d1)
> 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
>         # https://git.kernel.org/pub/scm/linux/kernel/git/jic23/iio.git/commit/?id=d4e1a549566b9ea8b96e80f0cdcbe99714ac256e
>         git remote add jic23-iio https://git.kernel.org/pub/scm/linux/kernel/git/jic23/iio.git
>         git fetch --no-tags jic23-iio testing
>         git checkout d4e1a549566b9ea8b96e80f0cdcbe99714ac256e
>         # save the config file
>         mkdir build_dir && cp config build_dir/.config
>         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash drivers/iio/adc/
> 
> If you fix the issue, kindly add following tag where applicable
> | Reported-by: kernel test robot <lkp@...el.com>
> 
> All warnings (new ones prefixed by >>):
> 
> >> drivers/iio/adc/mcp3911.c:274:6: warning: variable 'tmp0' set but not used [-Wunused-but-set-variable]  
>            int tmp0, tmp1;
>                ^
>    1 warning generated.
> 
> 
> vim +/tmp0 +274 drivers/iio/adc/mcp3911.c
> 
>    268	
>    269	static int mcp3911_calc_scale_table(struct mcp3911 *adc)
>    270	{
>    271		u32 ref = MCP3911_INT_VREF_MV;
>    272		u32 div;
>    273		int ret;
>  > 274		int tmp0, tmp1;  
>    275		s64 tmp2;
>    276	
>    277		if (adc->vref) {
>    278			ret = regulator_get_voltage(adc->vref);
>    279			if (ret < 0) {
>    280				dev_err(&adc->spi->dev,
>    281					"failed to get vref voltage: %d\n",
>    282				       ret);
>    283				return ret;
>    284			}
>    285	
>    286			ref = ret / 1000;
>    287		}
>    288	
>    289		/*
>    290		 * For 24-bit Conversion
>    291		 * Raw = ((Voltage)/(Vref) * 2^23 * Gain * 1.5
>    292		 * Voltage = Raw * (Vref)/(2^23 * Gain * 1.5)
>    293		 *
>    294		 * ref = Reference voltage
>    295		 * div = (2^23 * 1.5 * gain) = 12582912 * gain
>    296		 */
>    297		for (int i = 0; i < MCP3911_NUM_SCALES; i++) {
>    298			div = 12582912 * BIT(i);
>    299			tmp2 = div_s64((s64)ref * 1000000000LL, div);
>    300			tmp1 = div;
>    301			tmp0 = (int)div_s64_rem(tmp2, 1000000000, &tmp1);

Marcus, 
I'm guessing the intent here is just to get the remainder.  
Hence fix is probably just to drop tmp0?

If you confirm that I'll tweak the commit to do that.

Jonathan


>    302	
>    303			mcp3911_scale_table[i][0] = 0;
>    304			mcp3911_scale_table[i][1] = tmp1;
>    305		}
>    306	
>    307		return 0;
>    308	}
>    309	
>