Implement GPIO Module

[jensdrenhaus]

GPIO (Buttons and Switches at DUT), support for one the following interfaces: sysfs, /dev/gpiomem

[jensdrenhaus]

Controlling GPIO (on the RaspberryPi) via sysfs seems to be deprecated.

Using memory mapping with /dev/gpiomem seems to be the most basic and straight forward option. There is golang library go-rpio implementing that.
Although the last contributions are more than 3 years old, it is highly rated (2.2k stars)
A potential drawback on the first look might be, that it uses /dev/mem by default and only falls back to dev/gpiomem if the Linux user has no root privileges.

There is also a newer interface to GPIO via Linux character device [1], which is recommende by the Raspberry Pi Foundation. This approach is also already implemented in the golang library gpiocdev .
It seems a bit more sophisticated but also a bit bloated.

I tend to stick with the dev/gpiomem approach, but character device seems to be the new way to go.

[1] https://pip.raspberrypi.com/categories/685-whitepapers-app-notes/documents/RP-006553-WP/A-history-of-GPIO-usage-on-Raspberry-Pi-devices-and-current-best-practices.pdf

[jensdrenhaus]

@sylv-io any thoughts on this?

[sylv-io]

@sylv-io any thoughts on this?

IMHO we should support gpiomem and sysfs as separate dutctl gpio modules 👍
We can then prioritize the use of gpiomem and still fall back to sysfs if it is not available.

[jensdrenhaus]

What about that newer kernel interface via character device? Leave it out completely for now?

[sylv-io]

Sure, we should support all possible GPIO interfaces. Either by adding a module that supports them all via module options, or by implementing a separate module for each interface. I think the former option fits the best.

[macpijan]

If I may add, sysfs GPIO is already marked as obsolete, and disabled by default. If you are looking for a future-proof solution, gpiocdev is likely the way to go.

As for the sysfs interface, maybe you find some of these useful: https://github.com/3mdeb/RteCtrl/blob/master/pkg/gpioControl/gpioControl.go