gpiomem [ODROID Wiki]

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Rootless GPIO access: /dev/gpiomem

/dev/gpiomem provides user with root-free access to the GPIO registers. Opening /dev/gpiomem device file and calling mmap() function will map the GPIO registers' memory map area to the user's pointer.
This driver is added in below's Ubuntu kernel versions:

ODROID-C2: 3.14.79-105 kernel version or later
ODROID-C0/C1+: 3.10.104-182 kernel version or later
ODROID-XU4: 4.9.x kernel version or later

How to enable gpiomem driver

/dev/gpiomem driver is included as module by default. In order to use gpiomem driver, it is necessary to configure account access permission.

$ sudo addgroup gpio
$ sudo usermod -a -G gpio odroid    
$ cat /etc/udev/rules.d/90-gpiomem.rules

ODROID-C0/C1+/C2

SUBSYSTEM=="meson-gpiomem", GROUP="gpio", MODE="0660"

ODROID-XU4

SUBSYSTEM=="exynos-gpiomem", GROUP="gpio", MODE="0660"