Dallas/Maxim DS1307 and similar I2C RTC chips

modulename: rtc-ds1307.ko

configname: CONFIG_RTC_DRV_DS1307

Linux Kernel Configuration
└─>Device Drivers
└─>Real Time Clock
└─>Dallas/Maxim DS1307 and similar I2C RTC chips
In linux kernel since version 2.6.20 (release Date: 2007-02-04)  
If you say yes here you get support for various compatible RTC
chips (often with battery backup) connected with I2C. This driver
should handle DS1307, DS1337, DS1338, DS1339, DS1340, ST M41T00,
and probably other chips. In some cases the RTC must already
have been initialized (by manufacturing or a bootloader).

The first seven registers on these chips hold an RTC, and other
registers may add features such as NVRAM, a trickle charger for
the RTC/NVRAM backup power, and alarms. This driver may not
expose all those available chip features.

This driver can also be built as a module. If so, the module
will be called rtc-ds1307.

source code: