[FEATURE]: GPIO handling for newer kernels

[szwenni]

Is your feature request related to a problem?

Yes

Description

Right now it is not possible to use GPIO buttons with newer kernels as the sysfs support was dropped where the onoff nodejs library was relying on.

Describe the solution you'd like

I'm currently working on a work in progress library which uses libgpiod to interface with GPIOs.
https://github.com/szwenni/libgpiod-node-wrapper

This issue should be used more or less as a discussion ticket.
The only point where I saw the usage of the GPIOs was here: https://github.com/PhotoboothProject/photobooth/blob/dev/assets/js/remotebuzzer-server.js

I'm aiming to provide a drop in replacement for onoff later on. For now I'm trying to find use cases what I additionally can test.
Currently I'm supporting reading, writing, watching, debouncing, info for lines, info for chips, listing chips and its labels and checking accessibility to the chips.
The problem is that I currently only have a RPI5 with kernel 6.6 to hand. I would like to get a few more tests before creating a pull request and publishing to npm.

Describe alternatives you've considered

I checked onoff, I think this is not developed anymore since a few years.
I checked libgpiod-node, but this only supports an old version of libgpiod (<2.x), the newer version which is in dev has no watch support up to this time.

Additional context

No response

[andi34]

I wasn't able to test, but I guess the already implemented way still works. Every gpio might need to be exported like this

echo 21 > /sys/class/gpio/export

To have the sysfs available.

In long term it would be great to have an alternative solution. I was thinking about rewriting the Remotebuzzer server in python which would still allow the connection as client from Photobooth.

If your having an alternative solution I am sure you'll find people in our telegram community to help on testing and debugging.

[szwenni]

Hi
Sadly is this not the case anymore. The GPIOs will have different numbers with different offsets e.g. GPIO 6 gets GPIO 518. In some cases the sys gpio layer does not even exist anymore as the distribution removed it and the plan is in future versions of the kernel to completly remove it.
I also read somewhere some days ago that the offsets cam change from boot to boot.

https://forums.raspberrypi.com/viewtopic.php?t=361116&start=125

This was the forum I orginally stumbled above. Especially the second post there.

Also just saw a hint in the faq for this problem:

https://photoboothproject.github.io/faq/#remotebuzzer-hardware-button-led-feature-using-gpio-connected-hardware-raspberry-pi-only

Rewriting in python as client to the server would also be a nice solution for the problem. I think there is already some support for the new way of handling GPIOs in some python libs.

I will try to connect all the stuff together and get a working solution which can be tested straight away.

[andi34]

The offset should be handled by PhotoboothProject/onoff@6e31639 and I agree that we need an different solution or remove it entirely from the project in future. Currently I am having only limited time for the project and concentrating on other adjustments.

[andi34]

When I looked last time the sysfs was enabled for all pi variants inside the PiOS kernel config. I am quite sure if needs the export to have the sysfs available on defined GPIO - might need the high value GPIO mapping. Most user would only have problems setting it up as it's complicated to setup via script automatically... which is why the note was added to the FAQ.