1.CONFIG_OF
在一些驱动中经常看到#ifdef CONFIG_OF，这里的OF是Open Firmware。
Open Firmware. This was invented long time ago when Apple was producing laptops based on PowerPC CPUs. Openfirmware provides a good description of the devices connected to the platform. In Linux kernel the part that works with device data is called Device Tree (DT). More details in the Usage model.
详细参考kernel\Documentation\devicetree\usage-model.txt