如果内存地址的值已更改，则进行有效检测？

This more a general question. Consider an external device. From time to time this device writes data via its device driver to a specific memory address. I want to write a small C program which read out this data. Is there a better way than just polling this address to check if the value has been changed? I want to keep the CPU load low.This more a general question. Consider an exter