define macro in xcode

ex:

configuration: Debug

gcc 4.0 processing-> preprocessor macros:   _DEBUG

combine c and c++ for apple driver

set build option:

gcc 4.0 language -->  compile source as -->  c++

info.plist for driver

IOMatchCategory:

set IODefaultMatchCategory to compare with other driver

the driver with higher probe score will win

IOLog

print message in the kernel

the message is stored at /var/log/system.log