linux-kernel - [jic23-iio:testing 21/30] drivers/iio/adc/at91-sama5d2_adc.c:790:11: warning: variable 'nbits' is used uninitialized whenever 'if' condition is false

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Date:   Mon, 1 Aug 2022 07:30:35 +0800
From:   kernel test robot <lkp@...el.com>
To:     Claudiu Beznea <claudiu.beznea@...rochip.com>
Cc:     llvm@...ts.linux.dev, kbuild-all@...ts.01.org,
        linux-kernel@...r.kernel.org,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>
Subject: [jic23-iio:testing 21/30] drivers/iio/adc/at91-sama5d2_adc.c:790:11:
 warning: variable 'nbits' is used uninitialized whenever 'if' condition is
 false

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/jic23/iio.git testing
head:   e776e5ec0a21cc38f5e853d4dc98845d6e7f76b0
commit: 1c890d33c115b6331d8df8c06e46d3fc4e4e9d42 [21/30] iio: adc: at91-sama5d2_adc: adjust osr based on specific platform data
config: arm-randconfig-r026-20220731 (https://download.01.org/0day-ci/archive/20220801/202208010745.QZRYCihu-lkp@intel.com/config)
compiler: clang version 16.0.0 (https://github.com/llvm/llvm-project 52cd00cabf479aa7eb6dbb063b7ba41ea57bce9e)
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 arm cross compiling tool for clang build
        # apt-get install binutils-arm-linux-gnueabi
        # https://git.kernel.org/pub/scm/linux/kernel/git/jic23/iio.git/commit/?id=1c890d33c115b6331d8df8c06e46d3fc4e4e9d42
        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 1c890d33c115b6331d8df8c06e46d3fc4e4e9d42
        # 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=arm 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/at91-sama5d2_adc.c:790:11: warning: variable 'nbits' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
           else if (st->oversampling_ratio == 16)
                    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
   drivers/iio/adc/at91-sama5d2_adc.c:797:48: note: uninitialized use occurs here
           diff = st->soc_info.platform->chan_realbits - nbits;
                                                         ^~~~~
   drivers/iio/adc/at91-sama5d2_adc.c:790:7: note: remove the 'if' if its condition is always true
           else if (st->oversampling_ratio == 16)
                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   drivers/iio/adc/at91-sama5d2_adc.c:784:11: note: initialize the variable 'nbits' to silence this warning
           int nbits, diff;
                    ^
                     = 0
   1 warning generated.


vim +790 drivers/iio/adc/at91-sama5d2_adc.c

   781	
   782	static int at91_adc_adjust_val_osr(struct at91_adc_state *st, int *val)
   783	{
   784		int nbits, diff;
   785	
   786		if (st->oversampling_ratio == 1)
   787			nbits = 12;
   788		else if (st->oversampling_ratio == 4)
   789			nbits = 13;
 > 790		else if (st->oversampling_ratio == 16)
   791			nbits = 14;
   792	
   793		/*
   794		 * We have nbits of real data and channel is registered as
   795		 * st->soc_info.platform->chan_realbits, so shift left diff bits.
   796		 */
   797		diff = st->soc_info.platform->chan_realbits - nbits;
   798		*val <<= diff;
   799	
   800		return IIO_VAL_INT;
   801	}
   802	

-- 
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