/sys/class/gpio/... (sysfs interface)

configname: CONFIG_GPIO_SYSFS

Linux Kernel Configuration
└─>Device Drivers
└─>GPIO Support
└─>/sys/class/gpio/... (sysfs interface)
In linux kernel since version 2.6.27 (release Date: 2008-10-09)  
Say Y here to add a sysfs interface for GPIOs.

This is mostly useful to work around omissions in a system's
kernel support. Those are common in custom and semicustom
hardware assembled using standard kernels with a minimum of
custom patches. In those cases, userspace code may import
a given GPIO from the kernel, if no kernel driver requested it.

Kernel drivers may also request that a particular GPIO be
exported to userspace; this can be useful when debugging.

depends
CONFIG_EXPERIMENTAL
CONFIG_GPIOLIB
CONFIG_SYSFS