Find replacement for unsupported WiringPi library

[zehnm]

Expected Behavior or Design

All 3rd party libraries are maintained and if possible supported by Buildroot.

Current Behavior or Design

GPIO access and i2c communication are handled with the WiringPi library.
This library has been deprecated in August 2019 and is no longer maintained: http://wiringpi.com/wiringpi-deprecated/
Furthermore it has been removed in the latest Builroot version 2020.05.

Possible Solution

• Keep WiringPi.
  It still works great at the moment and the source code is available.
  However, we have to manually include it as custom package in new Buildroot versions. It may also break in future Kernel or RPi firmware releases.
• Look around for an alternative GPIO / i2c library.
  I'm not aware of a successor library though.
• Use the new native Linux gpio/spio/i2c/… support for the BCM platform.
  • libgpiod might be the new standard way of interacting with GPIO devices.
  • SMBus seems to be the preferred way of communicating with i2c devices in Linux

Detailed Description and Additional Information

From libgpiod: Since linux 4.8 the GPIO sysfs interface is deprecated. User space should use the character device instead.

Personally, I'd prefer to go the standard Linux Kernel route.
If you have any suggestions, please comment.

[zehnm]

After testing direct SMBus communication and digging around the WiringPi library, the effort wouldn't be too big replacing WiringPi. However, WiringPi already uses SMBus for i2c! Therefore I don't see an urgent need replacing WiringPi, as long as we can still easily use it in Buildroot.
I still need to look into libgpiod though.

[zehnm]

Small update: in remote-os we are now using a custom Buildroot package for a forked WirkingPi repo, since the original repository is no longer online and official Buildroot support has been removed.