Subject: Re: [PATCH v2] iio: core: Fix IIO_VAL_FRACTIONAL calculation for negative values

From: Dan Carpenter <[email-masked]>
Date: Mon, 31 Aug 2020 12:51:52 +0300

Hi Anand,

url:    https://github.com/0day-ci/linux/commits/Anand-Ashok-Dumbre/iio-core-Fix-IIO_VAL_FRACTIONAL-calculation-for-negative-values/20200827-021613
base:   https://git.kernel.org/pub/scm/linux/kernel/git/jic23/iio.git togreg
config: x86_64-randconfig-m001-20200826 (attached as .config)
compiler: gcc-9 (Debian 9.3.0-15) 9.3.0

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <[email-masked]>
Reported-by: Dan Carpenter <[email-masked]>

smatch warnings:
drivers/iio/industrialio-core.c:620 __iio_format_value() error: uninitialized symbol 'tmp'.

# https://github.com/0day-ci/linux/commit/c66f94e17db7eca581318d225d1fb41c56aced08
git remote add linux-review https://github.com/0day-ci/linux
git fetch --no-tags linux-review Anand-Ashok-Dumbre/iio-core-Fix-IIO_VAL_FRACTIONAL-calculation-for-negative-values/20200827-021613
git checkout c66f94e17db7eca581318d225d1fb41c56aced08
vim +/tmp +620 drivers/iio/industrialio-core.c

51239600074bc9 drivers/iio/industrialio-core.c         Jonathan Cameron    2016-11-08  590  static ssize_t __iio_format_value(char *buf, size_t len, unsigned int type,
51239600074bc9 drivers/iio/industrialio-core.c         Jonathan Cameron    2016-11-08  591  				  int size, const int *vals)
1d892719e70e47 drivers/staging/iio/industrialio-core.c Jonathan Cameron    2011-05-18  592  {
7985e7c1003bc5 drivers/iio/industrialio-core.c         Lars-Peter Clausen  2012-09-14  593  	unsigned long long tmp;
51239600074bc9 drivers/iio/industrialio-core.c         Jonathan Cameron    2016-11-08  594  	int tmp0, tmp1;
c66f94e17db7ec drivers/iio/industrialio-core.c         Anand Ashok Dumbre  2020-08-26  595  	s64 tmp2;
67eedba39ed1ac drivers/iio/industrialio-core.c         Michael Hennerich   2012-05-11  596  	bool scale_db = false;
1d892719e70e47 drivers/staging/iio/industrialio-core.c Jonathan Cameron    2011-05-18  597  
3661f3f5e961f7 drivers/iio/industrialio-core.c         Lars-Peter Clausen  2013-10-07  598  	switch (type) {
67eedba39ed1ac drivers/iio/industrialio-core.c         Michael Hennerich   2012-05-11  599  	case IIO_VAL_INT:
35a4eeb055c9c3 drivers/iio/industrialio-core.c         Takashi Iwai        2020-03-11  600  		return scnprintf(buf, len, "%d", vals[0]);
67eedba39ed1ac drivers/iio/industrialio-core.c         Michael Hennerich   2012-05-11  601  	case IIO_VAL_INT_PLUS_MICRO_DB:
67eedba39ed1ac drivers/iio/industrialio-core.c         Michael Hennerich   2012-05-11  602  		scale_db = true;
9d793c1a7f25d7 drivers/iio/industrialio-core.c         Gustavo A. R. Silva 2017-11-08  603  		/* fall through */
67eedba39ed1ac drivers/iio/industrialio-core.c         Michael Hennerich   2012-05-11  604  	case IIO_VAL_INT_PLUS_MICRO:
9fbfb4b37ed23f drivers/iio/industrialio-core.c         Srinivas Pandruvada 2014-04-29  605  		if (vals[1] < 0)
35a4eeb055c9c3 drivers/iio/industrialio-core.c         Takashi Iwai        2020-03-11  606  			return scnprintf(buf, len, "-%d.%06u%s", abs(vals[0]),
8f57e4d930d482 drivers/iio/industrialio-core.c         Michal Nazarewicz   2016-01-15  607  					-vals[1], scale_db ? " dB" : "");
1d892719e70e47 drivers/staging/iio/industrialio-core.c Jonathan Cameron    2011-05-18  608  		else
35a4eeb055c9c3 drivers/iio/industrialio-core.c         Takashi Iwai        2020-03-11  609  			return scnprintf(buf, len, "%d.%06u%s", vals[0], vals[1],
67eedba39ed1ac drivers/iio/industrialio-core.c         Michael Hennerich   2012-05-11  610  					scale_db ? " dB" : "");
67eedba39ed1ac drivers/iio/industrialio-core.c         Michael Hennerich   2012-05-11  611  	case IIO_VAL_INT_PLUS_NANO:
9fbfb4b37ed23f drivers/iio/industrialio-core.c         Srinivas Pandruvada 2014-04-29  612  		if (vals[1] < 0)
35a4eeb055c9c3 drivers/iio/industrialio-core.c         Takashi Iwai        2020-03-11  613  			return scnprintf(buf, len, "-%d.%09u", abs(vals[0]),
9fbfb4b37ed23f drivers/iio/industrialio-core.c         Srinivas Pandruvada 2014-04-29  614  					-vals[1]);
71646e2c7ae4ed drivers/staging/iio/industrialio-core.c Michael Hennerich   2011-06-27  615  		else
35a4eeb055c9c3 drivers/iio/industrialio-core.c         Takashi Iwai        2020-03-11  616  			return scnprintf(buf, len, "%d.%09u", vals[0], vals[1]);
7985e7c1003bc5 drivers/iio/industrialio-core.c         Lars-Peter Clausen  2012-09-14  617  	case IIO_VAL_FRACTIONAL:
c66f94e17db7ec drivers/iio/industrialio-core.c         Anand Ashok Dumbre  2020-08-26  618  		tmp2 = div_s64((s64)vals[0] * 1000000000LL, vals[1]);
51239600074bc9 drivers/iio/industrialio-core.c         Jonathan Cameron    2016-11-08  619  		tmp1 = vals[1];
51239600074bc9 drivers/iio/industrialio-core.c         Jonathan Cameron    2016-11-08 @620  		tmp0 = (int)div_s64_rem(tmp, 1000000000, &tmp1);
                                                                                                                                ^^^
Probably "tmp2" was intended?

c66f94e17db7ec drivers/iio/industrialio-core.c         Anand Ashok Dumbre  2020-08-26  621  		if ((tmp2 < 0) && (tmp0 == 0))
c66f94e17db7ec drivers/iio/industrialio-core.c         Anand Ashok Dumbre  2020-08-26  622  			return snprintf(buf, len, "-0.%09u", abs(tmp1));
c66f94e17db7ec drivers/iio/industrialio-core.c         Anand Ashok Dumbre  2020-08-26  623  		else
c66f94e17db7ec drivers/iio/industrialio-core.c         Anand Ashok Dumbre  2020-08-26  624  			return snprintf(buf, len, "%d.%09u", tmp0, abs(tmp1));
103d9fb907058e drivers/iio/industrialio-core.c         Lars-Peter Clausen  2012-10-16  625  	case IIO_VAL_FRACTIONAL_LOG2:
7fd6592d128704 drivers/iio/industrialio-core.c         Nikolaus Schulz     2017-03-24  626  		tmp = shift_right((s64)vals[0] * 1000000000LL, vals[1]);
7fd6592d128704 drivers/iio/industrialio-core.c         Nikolaus Schulz     2017-03-24  627  		tmp0 = (int)div_s64_rem(tmp, 1000000000LL, &tmp1);
35a4eeb055c9c3 drivers/iio/industrialio-core.c         Takashi Iwai        2020-03-11  628  		return scnprintf(buf, len, "%d.%09u", tmp0, abs(tmp1));
9fbfb4b37ed23f drivers/iio/industrialio-core.c         Srinivas Pandruvada 2014-04-29  629  	case IIO_VAL_INT_MULTIPLE:
9fbfb4b37ed23f drivers/iio/industrialio-core.c         Srinivas Pandruvada 2014-04-29  630  	{
9fbfb4b37ed23f drivers/iio/industrialio-core.c         Srinivas Pandruvada 2014-04-29  631  		int i;
51239600074bc9 drivers/iio/industrialio-core.c         Jonathan Cameron    2016-11-08  632  		int l = 0;
9fbfb4b37ed23f drivers/iio/industrialio-core.c         Srinivas Pandruvada 2014-04-29  633  
51239600074bc9 drivers/iio/industrialio-core.c         Jonathan Cameron    2016-11-08  634  		for (i = 0; i < size; ++i) {
35a4eeb055c9c3 drivers/iio/industrialio-core.c         Takashi Iwai        2020-03-11  635  			l += scnprintf(&buf[l], len - l, "%d ", vals[i]);
51239600074bc9 drivers/iio/industrialio-core.c         Jonathan Cameron    2016-11-08  636  			if (l >= len)
51239600074bc9 drivers/iio/industrialio-core.c         Jonathan Cameron    2016-11-08  637  				break;
51239600074bc9 drivers/iio/industrialio-core.c         Jonathan Cameron    2016-11-08  638  		}
51239600074bc9 drivers/iio/industrialio-core.c         Jonathan Cameron    2016-11-08  639  		return l;
9fbfb4b37ed23f drivers/iio/industrialio-core.c         Srinivas Pandruvada 2014-04-29  640  	}
8cb3403633146a drivers/iio/industrialio-core.c         Andrea Merello      2019-11-20  641  	case IIO_VAL_CHAR:
35a4eeb055c9c3 drivers/iio/industrialio-core.c         Takashi Iwai        2020-03-11  642  		return scnprintf(buf, len, "%c", (char)vals[0]);
67eedba39ed1ac drivers/iio/industrialio-core.c         Michael Hennerich   2012-05-11  643  	default:
1d892719e70e47 drivers/staging/iio/industrialio-core.c Jonathan Cameron    2011-05-18  644  		return 0;
1d892719e70e47 drivers/staging/iio/industrialio-core.c Jonathan Cameron    2011-05-18  645  	}
67eedba39ed1ac drivers/iio/industrialio-core.c         Michael Hennerich   2012-05-11  646  }

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