bus.h contains reference to bus_if.h and device_if.h which are not found in the required directory

[shivanth]

I'm trying to write a  char driver and am having trouble including bus.h 
header file . This file tries to include the files bus_if.h and 
device_if.h. But these files are not found in /usr/src/sys/sys/ . 
Instead i found these files in usr/obj/usr/src/sys/GENERIC/ .
 I'm wondering there're many drivers using bus.h and are not broken , 
but my module never seems to compile . Am I wrong somewhere (I should be)?