drivers/gpu/drm/bridge/sil-sii8620.c:2405: undefined reference to `extcon_unregister_notifier'

[kbuild test robot]

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 
master
head:   625e2001e99e82ea3eb5b0370a428a4328b9166b
commit: eb27fde2731b6cb5818493b8ac18e01f427e335f eeprom: at24: drop redundant 
variable in at24_read()
date:   6 weeks ago
config: x86_64-randconfig-g0-05042232 (attached as .config)
compiler: gcc-4.9 (Debian 4.9.4-2) 4.9.4
reproduce:
        git checkout eb27fde2731b6cb5818493b8ac18e01f427e335f
        # save the attached .config to linux build tree
        make ARCH=x86_64 

All errors (new ones prefixed by >>):

   drivers/gpu/drm/bridge/sil-sii8620.o: In function `sii8620_remove':
>> /kbuild/src/smoke/drivers/gpu/drm/bridge/sil-sii8620.c:2405: undefined 
>> reference to `extcon_unregister_notifier'
   drivers/gpu/drm/bridge/sil-sii8620.o: In function `sii8620_extcon_work':
>> /kbuild/src/smoke/drivers/gpu/drm/bridge/sil-sii8620.c:2189: undefined 
>> reference to `extcon_get_state'
--
   drivers/gpu/drm/bridge/sil-sii8620.o: In function `sii8620_remove':
>> drivers/gpu/drm/bridge/sil-sii8620.c:2405: undefined reference to 
>> `extcon_unregister_notifier'
   drivers/gpu/drm/bridge/sil-sii8620.o: In function `sii8620_extcon_work':
>> drivers/gpu/drm/bridge/sil-sii8620.c:2189: undefined reference to 
>> `extcon_get_state'

vim +2405 drivers/gpu/drm/bridge/sil-sii8620.c

ce6e153f Andrzej Hajda 2016-10-10  2399  
ce6e153f Andrzej Hajda 2016-10-10  2400  static int sii8620_remove(struct 
i2c_client *client)
ce6e153f Andrzej Hajda 2016-10-10  2401  {
ce6e153f Andrzej Hajda 2016-10-10  2402         struct sii8620 *ctx = 
i2c_get_clientdata(client);
ce6e153f Andrzej Hajda 2016-10-10  2403  
68883844 Maciej Purski 2018-02-27  2404         if (ctx->extcon) {
68883844 Maciej Purski 2018-02-27 @2405                 
extcon_unregister_notifier(ctx->extcon, EXTCON_DISP_MHL,
68883844 Maciej Purski 2018-02-27  2406                                         
   &ctx->extcon_nb);
68883844 Maciej Purski 2018-02-27  2407                 
flush_work(&ctx->extcon_wq);
68883844 Maciej Purski 2018-02-27  2408                 if (ctx->cable_state > 
0)
68883844 Maciej Purski 2018-02-27  2409                         
sii8620_cable_out(ctx);
68883844 Maciej Purski 2018-02-27  2410         } else {
68883844 Maciej Purski 2018-02-27  2411                 sii8620_cable_out(ctx);
68883844 Maciej Purski 2018-02-27  2412         }
e25f1f7c Maciej Purski 2017-08-24  2413         drm_bridge_remove(&ctx->bridge);
ce6e153f Andrzej Hajda 2016-10-10  2414  
ce6e153f Andrzej Hajda 2016-10-10  2415         return 0;
ce6e153f Andrzej Hajda 2016-10-10  2416  }
ce6e153f Andrzej Hajda 2016-10-10  2417  

:::::: The code at line 2405 was first introduced by commit
:::::: 688838442147d9dd94c2ef7c2c31a35cf150c5fa drm/bridge/sii8620: use 
micro-USB cable detection logic to detect MHL

:::::: TO: Maciej Purski <m.pur...@samsung.com>
:::::: CC: Chanwoo Choi <cw00.c...@samsung.com>

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