PC-style 'CMOS'

modulename: rtc_cmos_setup.ko

and/or

rtc-cmos.ko

configname: CONFIG_RTC_DRV_CMOS

Linux Kernel Configuration
└─>Device Drivers
└─>Real Time Clock
└─>PC-style 'CMOS'
In linux kernel since version 2.6.21.1 (release Date: 2007-04-27)  
Say "yes" here to get direct support for the real time clock
found in every PC or ACPI-based system, and some other boards.
Specifically the original MC146818, compatibles like those in
PC south bridges, the DS12887 or M48T86, some multifunction
or LPC bus chips, and so on.

Your system will need to define the platform device used by
this driver, otherwise it won't be accessible. This means
you can safely enable this driver if you don't know whether
or not your board has this kind of hardware.

This driver can also be built as a module. If so, the module
will be called rtc-cmos.

source code: