Klipper Compiling Error

pi@octopi:~/klipper $ make
  Compiling out/src/i2ccmds.o
src/i2ccmds.c:14:23: error: field ‘i2c_config’ has incomplete type
     struct i2c_config i2c_config;
                       ^
src/i2ccmds.c: In function ‘command_config_i2c’:
src/i2ccmds.c:23:23: warning: implicit declaration of function ‘i2c_setup’ [-Wimplicit-function-declaration]
     i2c->i2c_config = i2c_setup(args[1], args[2], addr);
                       ^
src/i2ccmds.c: In function ‘command_i2c_write’:
src/i2ccmds.c:35:5: warning: implicit declaration of function ‘i2c_write’ [-Wimplicit-function-declaration]
     i2c_write(i2c->i2c_config, data_len, data);
     ^
src/i2ccmds.c: In function ‘command_i2c_read’:
src/i2ccmds.c:48:5: warning: implicit declaration of function ‘i2c_read’ [-Wimplicit-function-declaration]
     i2c_read(i2c->i2c_config, reg_len, reg, data_len, data);
     ^
make: *** [Makefile:64: out/src/i2ccmds.o] Error 1
pi@octopi:~/klipper $