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Date:   Mon, 26 Sep 2022 13:09:02 +0300
From:   Dan Carpenter <dan.carpenter@oracle.com>
To:     kbuild@lists.01.org, Andrea Merello <andrea.merello@iit.it>
Cc:     lkp@intel.com, kbuild-all@lists.01.org,
        linux-kernel@vger.kernel.org,
        Jonathan Cameron <Jonathan.Cameron@huawei.com>,
        Andy Shevchenko <andy.shevchenko@gmail.com>
Subject: [jic23-iio:testing 44/63] drivers/iio/imu/bno055/bno055.c:635
 bno055_set_regmask() error: uninitialized symbol 'best_delta'.
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tree:   https://git.kernel.org/pub/scm/linux/kernel/git/jic23/iio.git testing
head:   df957373c1649c74b78bf2fcfd144f0c3baa68a5
commit: 50fe984f376abb4a00f80e13f51465ef09c2bde7 [44/63] iio: imu: add BNO055 I2C driver
config: s390-randconfig-m031-20220925
compiler: s390-linux-gcc (GCC) 12.1.0

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@intel.com>
| Reported-by: Dan Carpenter <dan.carpenter@oracle.com>

New smatch warnings:
drivers/iio/imu/bno055/bno055.c:635 bno055_set_regmask() error: uninitialized symbol 'best_delta'.
drivers/iio/imu/bno055/bno055.c:643 bno055_set_regmask() error: uninitialized symbol 'hwval'.
drivers/iio/imu/bno055/bno055.c:1511 bno055_trigger_handler() error: uninitialized symbol 'xfer_start'.
drivers/iio/imu/bno055/bno055.c:1513 bno055_trigger_handler() error: uninitialized symbol 'prev_end'.

Old smatch warnings:
drivers/iio/imu/bno055/bno055.c:649 bno055_set_regmask() error: uninitialized symbol 'hwval'.

vim +/best_delta +635 drivers/iio/imu/bno055/bno055.c

4aefe1c2bd0cb0 Andrea Merello 2022-09-07  579  static int bno055_set_regmask(struct bno055_priv *priv, int val, int val2,
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  580  			      int reg, int mask, struct bno055_sysfs_attr *attr)
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  581  {
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  582  	const int shift = __ffs(mask);
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  583  	int best_delta;
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  584  	int req_val;
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  585  	int tbl_val;
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  586  	bool first;
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  587  	int delta;
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  588  	int hwval;
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  589  	int ret;
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  590  	int len;
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  591  	int i;
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  592  
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  593  	/*
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  594  	 * The closest value the HW supports is only one in fusion mode,
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  595  	 * and it is autoselected, so don't do anything, just return OK,
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  596  	 * as the closest possible value has been (virtually) selected
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  597  	 */
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  598  	if (priv->operation_mode != BNO055_OPR_MODE_AMG)
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  599  		return 0;
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  600  
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  601  	len = attr->len;
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  602  
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  603  	/*
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  604  	 * We always get a request in INT_PLUS_MICRO, but we
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  605  	 * take care of the micro part only when we really have
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  606  	 * non-integer tables. This prevents 32-bit overflow with
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  607  	 * larger integers contained in integer tables.
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  608  	 */
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  609  	req_val = val;
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  610  	if (attr->type != IIO_VAL_INT) {
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  611  		len /= 2;
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  612  		req_val = min(val, 2147) * 1000000 + val2;
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  613  	}
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  614  
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  615  	first = true;
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  616  	for (i = 0; i < len; i++) {
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  617  		switch (attr->type) {
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  618  		case IIO_VAL_INT:
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  619  			tbl_val = attr->vals[i];
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  620  			break;
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  621  		case IIO_VAL_INT_PLUS_MICRO:
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  622  			WARN_ON(attr->vals[i * 2] > 2147);
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  623  			tbl_val = attr->vals[i * 2] * 1000000 +
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  624  				attr->vals[i * 2 + 1];
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  625  			break;
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  626  		case IIO_VAL_FRACTIONAL:
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  627  			WARN_ON(attr->vals[i * 2] > 4294);
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  628  			tbl_val = attr->vals[i * 2] * 1000000 /
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  629  				attr->vals[i * 2 + 1];
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  630  			break;
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  631  		default:
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  632  			return -EINVAL;
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  633  		}
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  634  		delta = abs(tbl_val - req_val);
4aefe1c2bd0cb0 Andrea Merello 2022-09-07 @635  		if (delta < best_delta || first) {

These tests need to be reversed to prevent reading uninitialized data.

	if (first || delta < best_delta) {

It's the correct thing to do.  KMsan will detect this at run time.  It's
undefined to read uninitialized data.

4aefe1c2bd0cb0 Andrea Merello 2022-09-07  636  			best_delta = delta;
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  637  			hwval = i;
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  638  			first = false;
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  639  		}
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  640  	}
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  641  
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  642  	if (attr->hw_xlate)
4aefe1c2bd0cb0 Andrea Merello 2022-09-07 @643  		hwval = attr->hw_xlate[hwval];


This one is likely a false positive but it's not feasible for the
kbuild bot to use cross function data so it does not know that
attr->len must be greater than zero.

4aefe1c2bd0cb0 Andrea Merello 2022-09-07  644  
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  645  	ret = bno055_operation_mode_do_set(priv, BNO055_OPR_MODE_CONFIG);
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  646  	if (ret)
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  647  		return ret;
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  648  
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  649  	ret = regmap_update_bits(priv->regmap, reg, mask, hwval << shift);
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  650  	if (ret)
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  651  		return ret;
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  652  
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  653  	return bno055_operation_mode_do_set(priv, BNO055_OPR_MODE_AMG);
4aefe1c2bd0cb0 Andrea Merello 2022-09-07  654  }