tree:   https://kernel.googlesource.com/pub/scm/linux/kernel/git/rafael/linux-pm.git bleeding-edge
head:   79f0d67a241f0583b994c73437caa54a4e942737
commit: 73d2bcced00671c2b724a31c3a4b3401c3e278d0 [175/181] cpuidle: allow governor switch on cpuidle_register_driver()
config: arm-defconfig (attached as .config)
compiler: arm-linux-gnueabi-gcc (GCC) 7.4.0
reproduce:
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        git checkout 73d2bcced00671c2b724a31c3a4b3401c3e278d0
        # save the attached .config to linux build tree
        GCC_VERSION=7.4.0 make.cross ARCH=arm 

If you fix the issue, kindly add following tag
Reported-by: kbuild test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

   drivers/cpuidle/driver.c: In function 'cpuidle_register_driver':
>> drivers/cpuidle/driver.c:270:4: error: 'cpuidle_prev_governor' undeclared (first use in this function); did you mean 'cpuidle_find_governor'?
       cpuidle_prev_governor = cpuidle_curr_governor;
       ^~~~~~~~~~~~~~~~~~~~~
       cpuidle_find_governor
   drivers/cpuidle/driver.c:270:4: note: each undeclared identifier is reported only once for each function it appears in
   drivers/cpuidle/driver.c: In function 'cpuidle_unregister_driver':
   drivers/cpuidle/driver.c:301:6: error: 'cpuidle_prev_governor' undeclared (first use in this function); did you mean 'cpuidle_find_governor'?
     if (cpuidle_prev_governor) {
         ^~~~~~~~~~~~~~~~~~~~~
         cpuidle_find_governor

vim +270 drivers/cpuidle/driver.c

   245	
   246	/**
   247	 * cpuidle_register_driver - registers a driver
   248	 * @drv: a pointer to a valid struct cpuidle_driver
   249	 *
   250	 * Register the driver under a lock to prevent concurrent attempts to
   251	 * [un]register the driver from occuring at the same time.
   252	 *
   253	 * Returns 0 on success, a negative error code (returned by
   254	 * __cpuidle_register_driver()) otherwise.
   255	 */
   256	int cpuidle_register_driver(struct cpuidle_driver *drv)
   257	{
   258		struct cpuidle_governor *gov;
   259		int ret;
   260	
   261		spin_lock(&cpuidle_driver_lock);
   262		ret = __cpuidle_register_driver(drv);
   263		spin_unlock(&cpuidle_driver_lock);
   264	
   265		if (!ret && !strlen(param_governor) && drv->governor &&
   266		    (cpuidle_get_driver() == drv)) {
   267			mutex_lock(&cpuidle_lock);
   268			gov = cpuidle_find_governor(drv->governor);
   269			if (gov) {
 > 270				cpuidle_prev_governor = cpuidle_curr_governor;
   271				if (cpuidle_switch_governor(gov) < 0)
   272					cpuidle_prev_governor = NULL;
   273			}
   274			mutex_unlock(&cpuidle_lock);
   275		}
   276	
   277		return ret;
   278	}
   279	EXPORT_SYMBOL_GPL(cpuidle_register_driver);
   280	

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