Just an example. You can use kextstat command to check the kernel
extension being loaded in the system.
MyMacMini:examples xiaofanc$ ./simple
Initialized libftdi 1.2 (major: 1, minor: 2, micro: 0, snapshot ver: unknown)
unable to open ftdi device: -5 (unable to claim usb device. Make sure
the default FTDI driver is not in use)