Microchip MCP23S08 I/O expander

modulename: mcp23s08.ko

and/or

gpio-mcp23s08.ko

configname: CONFIG_GPIO_MCP23S08

Linux Kernel Configuration
└─>Device Drivers
└─>GPIO Support
└─>Microchip MCP23S08 I/O expander
In linux kernel since version 2.6.25 (release Date: 2008-04-16)  
SPI driver for Microchip MCP23S08 I/O expander. This provides
a GPIO interface supporting inputs and outputs.

source code: