/dev/i2c1 gone with newer kernels versions

[CDit]

I use a Raspberry Pi 5 and use I2C1 with external eeprom.

 

With v25.5.1 up to kernel 6.6.63-current-bcm2711, /dev/i2c-1 is there (activated in /boot/firmware/config.txt with dtparam=i2c_arm=on) and communication with eeprom works fine.

 

With newer kernel versions, communication works not, /dev/i2c-1 does not exist anymore in this case without changing any configuration, just selected newer kernel using armbian-config

 

Any ideas why this happens?

Edited July 1 by CDit

[laibsch]

It appears that Heiko is the maintainer for RPi boards (all varieties?) in Armbian, but I believe @Igor also has the device and maybe he can repond.  I suggest you try to talk to Heiko and see if he has something to say.  I just perused the git sources and you might want to talk to Pander as well.

[Igor]

14 hours ago, CDit said:

Any ideas why this happens?

 

Feature regressions are expected - Linux kernel is complicated machinery and without spending hours, a day or a week investigating, it's usually not possible to tell. 

We don't touch Rpi kernels much. We have our own kernel config, but we use official Rpi sources, so I guess 1st step would be looking if someone reported something similar https://github.com/raspberrypi/linux/issues 

 

14 hours ago, CDit said:

selected newer kernel

By newer you mean 6.12.y, 6.16.y ... or 6.6.63 ->

[c0rnelius]

sudo modprobe i2c-dev ?

[Matthew White]

I hadn't done an upgrade but a fresh install;  (v25.5.1 for Raspberry Pi 3 Model B running Armbian Linux 6.12.28-current-bcm2711)

 

Realised that I had the same problem, only channel 2 was present; though I only realised  something was missing when I'd tried RaspberryOS on a Pi Zero with the same i2c device.

 

Adding to the /boot/config.txt didn't of itself solve the issue; adding the i2c1 to the armbian-config overlays also didn't see. 

 

However I did find the `/boot/firmware/config.txt`  that has a lot more settings, and seems to be where armbian-config  edits

 

Note the `dtparam-i2c_arm=on` line... which was commented out. Adding that back and it works... 
(well after figuring out I needed to level shift the i2c device but that's another story)

 

 

# For more options and information see
# http://rptl.io/configtxt
# Some settings may impact device functionality. See link above for details

# Uncomment some or all of these to enable the optional hardware interfaces
dtparam=i2c_arm=on
#dtparam=i2s=on
#dtparam=spi=on

# ..
dtoverlay=dwc2 i2c0 i2c1 i2c-gpio vc4-kms-v3d

 

 

[CaWeissWz]

I encountered the same issue using a custom v25.08 "RPi4b" image with kernel 6.12.37-current-bcm2711.

 

I found out, that adding the following line to /boot/firmware/config.txt brings back the missing i2c device:

Zitat

dtoverlay=i2c1-pi5

 

However, this used to happen automatically with the old "RPi5" images.