Re: [PATCH] drivers: rtc: handle OTF clock changes

Hi Elad,

kernel test robot noticed the following build warnings:

https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Elad-Nachman/drivers-rtc-handle-OTF-clock-changes/20260806-231215
base:   https://git.kernel.org/pub/scm/linux/kernel/git/abelloni/linux.git rtc-next
patch link:    https://lore.kernel.org/r/20260624123103.3523728-1-enachman%40marvell.com
patch subject: [PATCH] drivers: rtc: handle OTF clock changes
config: i386-randconfig-141 (https://download.01.org/0day-ci/archive/20260807/[email protected]/config)
compiler: gcc-14 (Debian 14.2.0-19) 14.2.0
smatch: v0.5.0-9187-g5189e3fb

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 <[email protected]>
| Reported-by: Dan Carpenter <[email protected]>
| Closes: https://lore.kernel.org/r/[email protected]/

smatch warnings:
drivers/rtc/interface.c:163 rtc_set_time() warn: variable dereferenced before check 'rtc' (see line 135)

vim +/rtc +163 drivers/rtc/interface.c

ab6a2d70d18edc David Brownell    2007-05-08  126  int rtc_set_time(struct rtc_device *rtc, struct rtc_time *tm)
0c86edc0d49706 Alessandro Zummo  2006-03-27  127  {
7e7c005b4b1f1f Alexandre Belloni 2019-10-21  128  	int err, uie;
37b82b16c5f104 Elad Nachman      2026-06-24  129  	struct rtc_time new_tm;
0c86edc0d49706 Alessandro Zummo  2006-03-27  130  
0c86edc0d49706 Alessandro Zummo  2006-03-27  131  	err = rtc_valid_tm(tm);
0c86edc0d49706 Alessandro Zummo  2006-03-27  132  	if (err != 0)
0c86edc0d49706 Alessandro Zummo  2006-03-27  133  		return err;
0c86edc0d49706 Alessandro Zummo  2006-03-27  134  
4c4e5df1f346f7 Baolin Wang       2018-01-08 @135  	err = rtc_valid_range(rtc, tm);
4c4e5df1f346f7 Baolin Wang       2018-01-08  136  	if (err)
4c4e5df1f346f7 Baolin Wang       2018-01-08  137  		return err;
71db049e7355f3 Alexandre Belloni 2018-02-17  138  
989515647e7832 Baolin Wang       2018-01-08  139  	rtc_subtract_offset(rtc, tm);
989515647e7832 Baolin Wang       2018-01-08  140  
7e7c005b4b1f1f Alexandre Belloni 2019-10-21  141  #ifdef CONFIG_RTC_INTF_DEV_UIE_EMUL
7e7c005b4b1f1f Alexandre Belloni 2019-10-21  142  	uie = rtc->uie_rtctimer.enabled || rtc->uie_irq_active;
7e7c005b4b1f1f Alexandre Belloni 2019-10-21  143  #else
7e7c005b4b1f1f Alexandre Belloni 2019-10-21  144  	uie = rtc->uie_rtctimer.enabled;
7e7c005b4b1f1f Alexandre Belloni 2019-10-21  145  #endif
7e7c005b4b1f1f Alexandre Belloni 2019-10-21  146  	if (uie) {
7e7c005b4b1f1f Alexandre Belloni 2019-10-21  147  		err = rtc_update_irq_enable(rtc, 0);
7e7c005b4b1f1f Alexandre Belloni 2019-10-21  148  		if (err)
7e7c005b4b1f1f Alexandre Belloni 2019-10-21  149  			return err;
7e7c005b4b1f1f Alexandre Belloni 2019-10-21  150  	}
7e7c005b4b1f1f Alexandre Belloni 2019-10-21  151  
0c86edc0d49706 Alessandro Zummo  2006-03-27  152  	err = mutex_lock_interruptible(&rtc->ops_lock);
0c86edc0d49706 Alessandro Zummo  2006-03-27  153  	if (err)
b68bb2632453a9 David Brownell    2008-07-29  154  		return err;
0c86edc0d49706 Alessandro Zummo  2006-03-27  155  
0c86edc0d49706 Alessandro Zummo  2006-03-27  156  	if (!rtc->ops)
0c86edc0d49706 Alessandro Zummo  2006-03-27  157  		err = -ENODEV;
bbccf83f6c4e1a Alessandro Zummo  2009-01-06  158  	else if (rtc->ops->set_time)
cd9662094edf41 David Brownell    2007-05-08  159  		err = rtc->ops->set_time(rtc->dev.parent, tm);
606cc43c720bde Alexandre Belloni 2019-03-20  160  	else
bbccf83f6c4e1a Alessandro Zummo  2009-01-06  161  		err = -EINVAL;
0c86edc0d49706 Alessandro Zummo  2006-03-27  162  
37b82b16c5f104 Elad Nachman      2026-06-24 @163  	if (rtc && rtc->ops && rtc->ops->read_time) {
                                                            ^^^
There is no point in checking "rtc" after we have already dereferenced
it.

37b82b16c5f104 Elad Nachman      2026-06-24  164  		if (!rtc->ops->read_time(rtc->dev.parent, &new_tm)) {
37b82b16c5f104 Elad Nachman      2026-06-24  165  			pr_debug("new rtc time secs %d mins %d hours %d mday %d mon %d year %d way %d yday %d dst %d\n",
37b82b16c5f104 Elad Nachman      2026-06-24  166  					new_tm.tm_sec, new_tm.tm_min,
37b82b16c5f104 Elad Nachman      2026-06-24  167  					new_tm.tm_hour, new_tm.tm_mday,
37b82b16c5f104 Elad Nachman      2026-06-24  168  					new_tm.tm_mon, new_tm.tm_year,
37b82b16c5f104 Elad Nachman      2026-06-24  169  					new_tm.tm_wday, new_tm.tm_yday,
37b82b16c5f104 Elad Nachman      2026-06-24  170  					new_tm.tm_isdst);
37b82b16c5f104 Elad Nachman      2026-06-24  171  		}
37b82b16c5f104 Elad Nachman      2026-06-24  172  	}
37b82b16c5f104 Elad Nachman      2026-06-24  173  
14d0e347ea2db5 Zoran Markovic    2013-06-26  174  	pm_stay_awake(rtc->dev.parent);
0c86edc0d49706 Alessandro Zummo  2006-03-27  175  	mutex_unlock(&rtc->ops_lock);
5f9679d29c7959 NeilBrown         2011-12-09  176  	/* A timer might have just expired */
5f9679d29c7959 NeilBrown         2011-12-09  177  	schedule_work(&rtc->irqwork);
29a1f599c0cc37 Baolin Wang       2017-12-14  178  
7e7c005b4b1f1f Alexandre Belloni 2019-10-21  179  	if (uie) {
7e7c005b4b1f1f Alexandre Belloni 2019-10-21  180  		err = rtc_update_irq_enable(rtc, 1);
7e7c005b4b1f1f Alexandre Belloni 2019-10-21  181  		if (err)
7e7c005b4b1f1f Alexandre Belloni 2019-10-21  182  			return err;
7e7c005b4b1f1f Alexandre Belloni 2019-10-21  183  	}
7e7c005b4b1f1f Alexandre Belloni 2019-10-21  184  
29a1f599c0cc37 Baolin Wang       2017-12-14  185  	trace_rtc_set_time(rtc_tm_to_time64(tm), err);
0c86edc0d49706 Alessandro Zummo  2006-03-27  186  	return err;
0c86edc0d49706 Alessandro Zummo  2006-03-27  187  }

--
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