Question about i2c_xxx function on CONFIG_I2C

[kuninori.morimoto.gx-zM6kxYcvzFBBDgjK7y7TUQ@public.gmane.org]

Dear all

I'm using i2c_xxx function on some board.
And sometimes I need very small kernel which doesn't need CONFIG_I2C.

But then (.config doesn't have CONFIG_I2C), the compile will fail.
like this

error: implicit declaration of function 'i2c_get_adapter'
error: implicit declaration of function 'i2c_transfer'

In this case, should I use #ifdef CONFIG_I2C in my code to solve this compile issue ?
Or is below #else in i2c.h good idea ?

--- i2c.h ---------
#if defined(CONFIG_I2C) || defined(CONFIG_I2C_MODULE)
...
extern struct i2c_adapter *i2c_get_adapter(int nr);
...
#else
...
#define i2c_get_adapter(nr) NULL
...
#endif


Best regards
---
Kuninori Morimoto