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

Marcus Folkesson
2022-09-22T19:56:03Z

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On Thu, Sep 22, 2022 at 11:59:25AM +0100, Jonathan Cameron wrote:
> On Thu, 22 Sep 2022 08:50:17 +0800
> kernel test robot <lkp@intel.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@intel.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?

Yes, the intention was to keep the remainder.
When I looked at the code a second time, tmp2 will have the
same value as the reminder as the division does not make sense.

So tmp1 and tmp0 is removed in the v7 patch.

/Marcus

>
> 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
> >
>

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