Hi John,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on dtor-input/next]
[also build test ERROR on hid/for-next linux/master linus/master v5.16-rc8 next-20220105]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/0day-ci/linux/commits/John-Sung/Add-serial-device-bus-support-to-penmount-serial-driver/20220106-175910
base:   https://git.kernel.org/pub/scm/linux/kernel/git/dtor/input.git next
config: arm-randconfig-r033-20220106 (https://download.01.org/0day-ci/archive/20220107/202201070309.lNqXfuTk-lkp(a)intel.com/config)
compiler: arm-linux-gnueabi-gcc (GCC) 11.2.0
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://github.com/0day-ci/linux/commit/053957cedaa900325f45620717607b464f532b54
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review John-Sung/Add-serial-device-bus-support-to-penmount-serial-driver/20220106-175910
        git checkout 053957cedaa900325f45620717607b464f532b54
        # save the config file to linux build tree
        mkdir build_dir
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.2.0 make.cross O=build_dir ARCH=arm SHELL=/bin/bash

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

All errors (new ones prefixed by >>):

   arm-linux-gnueabi-ld: drivers/input/touchscreen/penmount.o: in function `pm_serdev_remove':
>> penmount.c:(.text+0x2d4): undefined reference to `serdev_device_close'
   arm-linux-gnueabi-ld: drivers/input/touchscreen/penmount.o: in function `pm_serdev_probe':
>> penmount.c:(.text+0x5ec): undefined reference to `serdev_device_open'
>> arm-linux-gnueabi-ld: penmount.c:(.text+0x650): undefined reference to `serdev_device_set_baudrate'
>> arm-linux-gnueabi-ld: penmount.c:(.text+0x670): undefined reference to `serdev_device_set_flow_control'
>> arm-linux-gnueabi-ld: penmount.c:(.text+0x6a8): undefined reference to `serdev_device_write'
>> arm-linux-gnueabi-ld: penmount.c:(.text+0x6c0): undefined reference to `serdev_device_close'
   arm-linux-gnueabi-ld: drivers/input/touchscreen/penmount.o: in function `pm_init':
>> penmount.c:(.init.text+0x10): undefined reference to `__serdev_device_driver_register'

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