rtc实时时钟

config RTC_DRV_TEST
tristate "Test driver/device"
help
 If you say yes here you get support for the
 RTC test driver. It's a software RTC which can be
 used to test the RTC subsystem APIs. It gets
 the time from the system clock.
 You want this driver only if you are doing development
 on the RTC subsystem. Please read the source code
 for further details.


 This driver can also be built as a module. If so, the module

 will be called rtc-test.

这个选项模拟了一个rtc，使用的是系统内部驱动！！