linux-kernel - Re: drivers/iio/adc/axp20x_adc.c:572:26: sparse: sparse: dubious: x & !y

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Date: Sun, 7 Jan 2024 13:37:30 +0800
From: Chen-Yu Tsai <wens@...e.org>
To: kernel test robot <lkp@...el.com>
Cc: Aidan MacDonald <aidanmacdonald.0x0@...il.com>, oe-kbuild-all@...ts.linux.dev, 
	linux-kernel@...r.kernel.org, Jonathan Cameron <Jonathan.Cameron@...wei.com>, 
	Andy Shevchenko <andy.shevchenko@...il.com>
Subject: Re: drivers/iio/adc/axp20x_adc.c:572:26: sparse: sparse: dubious: x & !y

On Sun, Jan 7, 2024 at 9:30 AM kernel test robot <lkp@...el.com> wrote:
>
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> head:   52b1853b080a082ec3749c3a9577f6c71b1d4a90
> commit: 8957e5344353e9cd3f6b1e3004942e35449fa0e8 iio: adc: axp20x_adc: Minor code cleanups
> date:   10 months ago
> config: x86_64-randconfig-121-20240106 (https://download.01.org/0day-ci/archive/20240107/202401070901.68H00NFa-lkp@intel.com/config)
> compiler: ClangBuiltLinux clang version 17.0.6 (https://github.com/llvm/llvm-project 6009708b4367171ccdbf4b5905cb6a803753fe18)
> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240107/202401070901.68H00NFa-lkp@intel.com/reproduce)
>
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Reported-by: kernel test robot <lkp@...el.com>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202401070901.68H00NFa-lkp@intel.com/
>
> sparse warnings: (new ones prefixed by >>)
> >> drivers/iio/adc/axp20x_adc.c:572:26: sparse: sparse: dubious: x & !y
>    drivers/iio/adc/axp20x_adc.c:577:26: sparse: sparse: dubious: x & !y

This looks like a false positive. The code is doing exactly what we want:
val = val ? 1 : 0, but in a shorter format.

ChenYu

>
> vim +572 drivers/iio/adc/axp20x_adc.c
>
>    551
>    552  static int axp20x_write_raw(struct iio_dev *indio_dev,
>    553                              struct iio_chan_spec const *chan, int val, int val2,
>    554                              long mask)
>    555  {
>    556          struct axp20x_adc_iio *info = iio_priv(indio_dev);
>    557          unsigned int regmask, regval;
>    558
>    559          /*
>    560           * The AXP20X PMIC allows the user to choose between 0V and 0.7V offsets
>    561           * for (independently) GPIO0 and GPIO1 when in ADC mode.
>    562           */
>    563          if (mask != IIO_CHAN_INFO_OFFSET)
>    564                  return -EINVAL;
>    565
>    566          if (val != 0 && val != 700000)
>    567                  return -EINVAL;
>    568
>    569          switch (chan->channel) {
>    570          case AXP20X_GPIO0_V:
>    571                  regmask = AXP20X_GPIO10_IN_RANGE_GPIO0;
>  > 572                  regval = FIELD_PREP(AXP20X_GPIO10_IN_RANGE_GPIO0, !!val);
>    573                  break;
>    574
>    575          case AXP20X_GPIO1_V:
>    576                  regmask = AXP20X_GPIO10_IN_RANGE_GPIO1;
>    577                  regval = FIELD_PREP(AXP20X_GPIO10_IN_RANGE_GPIO1, !!val);
>    578                  break;
>    579
>    580          default:
>    581                  return -EINVAL;
>    582          }
>    583
>    584          return regmap_update_bits(info->regmap, AXP20X_GPIO10_IN_RANGE, regmask, regval);
>    585  }
>    586
>
> --
> 0-DAY CI Kernel Test Service
> https://github.com/intel/lkp-tests/wiki