[mac80211-next:master 25/25] net/mac80211/util.c:3411:8: error: implicit declaration of function 'cfg80211_iter_combinations'

[kbuild test robot <fengguang.wu@xxxxxxxxx>]

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/jberg/mac80211-next.git master
head:   9fd96261756ed32c762d417b2c4dfd1febbbf71c
commit: 9fd96261756ed32c762d417b2c4dfd1febbbf71c [25/25] cfg80211: don't export cfg80211_iter_combinations()
config: x86_64-randconfig-x019-201642 (attached as .config)
compiler: gcc-6 (Debian 6.2.0-3) 6.2.0 20160901
reproduce:
        git checkout 9fd96261756ed32c762d417b2c4dfd1febbbf71c
        # save the attached .config to linux build tree
        make ARCH=x86_64 

All errors (new ones prefixed by >>):

   net/mac80211/util.c: In function 'ieee80211_max_num_channels':
>> net/mac80211/util.c:3411:8: error: implicit declaration of function 'cfg80211_iter_combinations' [-Werror=implicit-function-declaration]
     err = cfg80211_iter_combinations(local->hw.wiphy, &params,
           ^~~~~~~~~~~~~~~~~~~~~~~~~~
   cc1: some warnings being treated as errors

vim +/cfg80211_iter_combinations +3411 net/mac80211/util.c

e227300c Purushottam Kushwaha 2016-10-12  3405  			ieee80211_chanctx_radar_detect(local, ctx);
6fa001bc Michal Kazior        2014-04-09  3406  	}
6fa001bc Michal Kazior        2014-04-09  3407  
6fa001bc Michal Kazior        2014-04-09  3408  	list_for_each_entry_rcu(sdata, &local->interfaces, list)
e227300c Purushottam Kushwaha 2016-10-12  3409  		params.iftype_num[sdata->wdev.iftype]++;
6fa001bc Michal Kazior        2014-04-09  3410  
e227300c Purushottam Kushwaha 2016-10-12 @3411  	err = cfg80211_iter_combinations(local->hw.wiphy, &params,
e227300c Purushottam Kushwaha 2016-10-12  3412  					 ieee80211_iter_max_chans,
6fa001bc Michal Kazior        2014-04-09  3413  					 &max_num_different_channels);
6fa001bc Michal Kazior        2014-04-09  3414  	if (err < 0)

:::::: The code at line 3411 was first introduced by commit
:::::: e227300c8395dffaa7614ce7c7666a82180ebc60 cfg80211: pass struct to interface combination check/iter

:::::: TO: Purushottam Kushwaha <pkushwah@xxxxxxxxxxxxxxxx>
:::::: CC: Johannes Berg <johannes.berg@xxxxxxxxx>

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