使程序有发现设备的能力和操作设备.它主要是用过一系列的回调函数来实现这些功能.像设置高频头的频率,帧频,视频压缩格式和图像像参数等等（在我写的FM驱动中就主要是设置频率，设置音量等）-The program has the ability to discover devices and operating equipment. It is primarily a series of callback functions used to achieve these functions. Tuner