Latest Bookworm GPIOChip weirdness

[oozeBot]

We recently began seeing issues with our custom build installing properly on RPi5s with the following error. Interestingly enough, our build installs just fine on a fresh copy of 64-bit Raspberry Pi OS, but fails after a full-upgrade.

[fatal] Failed to open IO device: Error 2. Can not open GPIO device file '/dev/gpiochip4'

I finally had time to dive into this and have noticed that gpiochip4 no longer exists and then becomes a pointer back to gpiochip0.

lrwxrwxrwx 1 root root           9 Apr 16 10:23 gpiochip4 -> gpiochip0

Reverting our build's config.json back to gpiochip0 fixes this and everything is now working as expected.

"GpioChipDevice": "/dev/gpiochip0",

@chrishamm - this is what I was trying to ask in this thread: https://forum.duet3d.com/post/353788 Switching this back to gpiochip0 allows our build to properly update the firmware from the command line.

Finally, if peer review proves this to be true, the documentation at the following GPIO Transfer Ready Pin section is now inaccurate. https://docs.duet3d.com/User_manual/Machine_configuration/DSF_Other

[chrishamm]

@oozeBot Thanks for pointing it out, I just removed the section about gpiochip4. The automatic change in config.json to gpiochip4 was removed last year and that change is already in the latest DuetPi version, so no further changes should be needed at this point if the stock image is used.