Fairchild FAN53555 Regulator

modulename: fan53555.ko

configname: CONFIG_REGULATOR_FAN53555

Linux Kernel Configuration
└─>Device Drivers
└─>Voltage and Current Regulator Support
└─>Fairchild FAN53555 Regulator
In linux kernel since version 3.1 (release Date: 2011-10-24)  
This driver supports Fairchild FAN53555 Digitally Programmable
TinyBuck Regulator. The FAN53555 is a step-down switching voltage
regulator that delivers a digitally programmable output from an
input voltage supply of 2.5V to 5.5V. The output voltage is
programmed through an I2C interface.

source code: