open,read,write都是POSIX标准的操作系统原语接口,具体操作哪个设备都是通过下面这个函数注册的设备接口来访问的,可以是文件、设备、socket等等
int iosDrvInstall
(
FUNCPTR pCreate, /* pointer to driver create function */
FUNCPTR pDelete, /* pointer to driver delete function */
FUNCPTR pOpen, /* pointer to driver open function */
FUNCPTR pClose, /* pointer to driver close function */
FUNCPTR pRead, /* pointer to driver read function */
FUNCPTR pWrite, /* pointer to driver write function */
FUNCPTR pIoctl /* pointer to driver ioctl function */
)