Kernel 6.6.47 changed the GPIO chip definition on Raspberry 5 and broke Seatalk1

[sailoog]

In previous kernels the GPIO chip definition was "gpiochip0" for Raspberry Pi 4 and "gpiochip4" for Raspberry Pi 5. Now both are "gpiochip0" in latest kernel. Seatalk1 in Signal K is broken for Raspberry Pi 5 right now. We should just change this to get it working again:

signalk-server/packages/streams/gpiod-seatalk.js

Line 47 in febea55

gpio_chip = "gpiochip4"

Waiting for @astuder to wake up to confirm :)

[astuder]

Grrr :(

I will add a check for kernel version (/proc/version, or Python's platform.version from a quick search).

[sbender9]

Why not make that configurable?

[astuder]

IMO the issue is a bit too low-level to confront users with.. even having to select the GPIO library is already border-line.

Seeing the error message reported in the OpenMarine forum, I think the simplest approach is to check for the file gpiochip4 and fall back to gpiochip0 if not present. That should keep working if Raspberry Pi foundation is flip-flopping on this change.

I will verify that with my Pi 5 later today.

[astuder]

Ok, looks a bit more complicated.
https://forums.raspberrypi.com/viewtopic.php?t=364196
I will investigate the method discussed in the PDF linked in the second post of that thread.

[sailoog]

Agree, this is a lot to ask to users because there is not much information documenting this.

It seems that there is a symlink /dev/gpiochip-rpi I will test this in different scenarios too.

[astuder]

Unless they just introduced it, I don't think /dev/gpiochip-rpi is available on a stock Pi image. At least its not present on my non-updated Pi 5.

[astuder]

@sailoog can you run this script on a system with the update?

import gpiod
c = 0
while gpiod.is_gpiochip_device(f"/dev/gpiochip{c}"):
  with gpiod.Chip(f"/dev/gpiochip{c}") as chip:
    info = chip.get_info()
    print(f"{info.name} [{info.label}] ({info.num_lines} lines)")
  c += 1

on my non-updated Pi 5 it returns

gpiochip0 [gpio-brcmstb@107d508500] (32 lines)
gpiochip1 [gpio-brcmstb@107d508520] (4 lines)
gpiochip2 [gpio-brcmstb@107d517c00] (17 lines)
gpiochip3 [gpio-brcmstb@107d517c20] (6 lines)
gpiochip4 [pinctrl-rp1] (54 lines)

[astuder]

I made a new image for the Pi 5. Of course, the script above doesn't work with gpiod v1.x. Here's the same script for v1.x:

import gpiod
print(f"gpiod v{gpiod.__version__}")
for chip in gpiod.ChipIter():
  print(f"{chip.name()} [{chip.label()}] ({chip.num_lines()} lines)")

on fresh new image, GPIO still is on gpiochip4:

gpiod v1.6.3
gpiochip0 [gpio-brcmstb@107d508500] (32 lines)
gpiochip1 [gpio-brcmstb@107d508520] (4 lines)
gpiochip2 [gpio-brcmstb@107d517c00] (17 lines)
gpiochip3 [gpio-brcmstb@107d517c20] (6 lines)
gpiochip4 [pinctrl-rp1] (54 lines)

My kernel version is 6.6.31.. will try to update that after lunch

[astuder]

Ok, that was quicker than expected. After running rpi-update I'm on kernel 6.6.50, and pinctrl-rp1 is now on gpiochip0:

gpiod v1.6.3
gpiochip0 [pinctrl-rp1] (54 lines)
gpiochip10 [gpio-brcmstb@107d508500] (32 lines)
gpiochip11 [gpio-brcmstb@107d508520] (4 lines)
gpiochip12 [gpio-brcmstb@107d517c00] (17 lines)
gpiochip13 [gpio-brcmstb@107d517c20] (6 lines)

So yes, I can reproduce.

[astuder]

Updated the gist to automatically detect gpiochip on Raspberry Pi 5.

@sailoog can you test this please?

[sailoog]

Tested on Raspberry 4 and 5, kernel 6.6.47 (stable), gpiod 1 and 2. No issues.

[tkurki]

Fixed by #1789