$ make
make -C /lib/modules/4.19.1/build M="$(pwd)" modules
make[1]: Entering directory '/usr/src/linux-4.19.1'
  CC [M]  /home/ergo/Downloads/bbswitch-0.8/bbswitch.o
/home/ergo/Downloads/bbswitch-0.8/bbswitch.c: In function 'bbswitch_proc_write':
/home/ergo/Downloads/bbswitch-0.8/bbswitch.c:317:9: error: implicit declaration of function 'copy_from_user'; did you mean 'raw_copy_from_user'? [-Werror=implicit-function-declaration]
     if (copy_from_user(cmd, buff, len))
         ^~~~~~~~~~~~~~
         raw_copy_from_user
cc1: some warnings being treated as errors
make[2]: *** [scripts/Makefile.build:312: /home/ergo/Downloads/bbswitch-0.8/bbswitch.o] Error 1
make[1]: *** [Makefile:1517: _module_/home/ergo/Downloads/bbswitch-0.8] Error 2
make[1]: Leaving directory '/usr/src/linux-4.19.1'
make: *** [Makefile:13: default] Error 2