linux/Documentation/ABI/testing/gpio-cdev

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What: /dev/gpiochip[0-9]+
Date: November 2015
KernelVersion: 4.4
Contact: linux-gpio@vger.kernel.org
Description:
The character device files /dev/gpiochip* are the interface
between GPIO chips and userspace.
The ioctl(2)-based ABI is defined in
[include/uapi]<linux/gpio.h> and documented in
Documentation/userspace-api/gpio/chardev.rst.
The following file operations are supported:
open(2)
Currently the only useful flags are O_RDWR.
ioctl(2)
Initiate various actions.
See Documentation/userspace-api/gpio/chardev.rst
for a description of all ioctls.
close(2)
Stops and free up the I/O contexts that was associated
with the file descriptor.
Users: TBD