arm-linux-gnueabi-ld: drivers/gpu/drm/bridge/sil-sii8620.c:2191: undefined reference to `extcon_register_notifier'

[kernel test robot]

Hi Masahiro,

FYI, the error/warning still remains.

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   22fbc037cd32e4e6771d2271b565806cfb8c134c
commit: def2fbffe62c00c330c7f41584a356001179c59c kconfig: allow symbols implied by y to become m
date:   7 months ago
config: arm-randconfig-p001-20201004 (attached as .config)
compiler: arm-linux-gnueabi-gcc (GCC) 9.3.0
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=def2fbffe62c00c330c7f41584a356001179c59c
        git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
        git fetch --no-tags linus master
        git checkout def2fbffe62c00c330c7f41584a356001179c59c
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross ARCH=arm 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@xxxxxxxxx>

All errors (new ones prefixed by >>):

   arm-linux-gnueabi-ld: drivers/gpu/drm/bridge/sil-sii8620.o: in function `sii8620_remove':
   drivers/gpu/drm/bridge/sil-sii8620.c:2355: undefined reference to `extcon_unregister_notifier'
   arm-linux-gnueabi-ld: drivers/gpu/drm/bridge/sil-sii8620.o: in function `sii8620_extcon_init':
   drivers/gpu/drm/bridge/sil-sii8620.c:2179: undefined reference to `extcon_find_edev_by_node'
>> arm-linux-gnueabi-ld: drivers/gpu/drm/bridge/sil-sii8620.c:2191: undefined reference to `extcon_register_notifier'
   arm-linux-gnueabi-ld: drivers/gpu/drm/bridge/sil-sii8620.o: in function `sii8620_extcon_work':
   drivers/gpu/drm/bridge/sil-sii8620.c:2139: undefined reference to `extcon_get_state'

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@xxxxxxxxxxxx

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