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no /dev/fan files on edge kerbnel v5.18.0



Fresh build edge bullseye image with kernel

Linux helios 5.18.0-rockchip64 #trunk SMP PREEMPT Sun May 29 20:19:27 EEST 2022 aarch64 GNU/Linux

fancontrol not work, because there no /dev/fan devices


How to get fancontrol back to work?

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On my system it are symlinks to /sys/..:

$ ls -l /dev/fan*
lrwxrwxrwx 1 root root 41 Feb 19 17:50 /dev/fan-p6 -> /sys/devices/platform/p6-fan/hwmon/hwmon6
lrwxrwxrwx 1 root root 41 Feb 19 17:50 /dev/fan-p7 -> /sys/devices/platform/p7-fan/hwmon/hwmon5


Those are generated by an udev rule:

$ cat /etc/udev/rules.d/90-helios64-hwmon.rules
# Helios64 persistent hwmon

ACTION=="remove", GOTO="helios64_hwmon_end"

KERNELS=="p6-fan", SUBSYSTEMS=="platform", ENV{_HELIOS64_FAN_}="p6", ENV{_IS_HELIOS64_FAN_}="1", ENV{IS_HELIOS64_HWMON}="1"
KERNELS=="p7-fan", SUBSYSTEMS=="platform", ENV{_HELIOS64_FAN_}="p7", ENV{_IS_HELIOS64_FAN_}="1", ENV{IS_HELIOS64_HWMON}="1"
KERNELS=="2-004c", SUBSYSTEMS=="i2c", DRIVERS=="lm75", ENV{IS_HELIOS64_HWMON}="1"

SUBSYSTEM!="hwmon", GOTO="helios64_hwmon_end"

ATTR{name}=="cpu", ENV{IS_HELIOS64_HWMON}="1", ENV{HELIOS64_SYMLINK}="/dev/thermal-cpu"
ENV{IS_HELIOS64_HWMON}=="1", ATTR{name}=="lm75", ENV{HELIOS64_SYMLINK}="/dev/thermal-board"
ENV{_IS_HELIOS64_FAN_}=="1", ENV{HELIOS64_SYMLINK}="/dev/fan-$env{_HELIOS64_FAN_}"

ENV{IS_HELIOS64_HWMON}=="1", RUN+="/bin/ln -sf $env{HWMON_PATH} $env{HELIOS64_SYMLINK}"



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I go by tree from ytour post /sys/devices/platform/p6-fan/hwmon/hwmon6 ans see no hwmon  in /sys/devices/platform/p6-fan(begin of lines removed):

root@helios64:/sys/devices/platform/p6-fan# ls -l
of_node -> ../../../firmware/devicetree/base/p6-fan
subsystem -> ../../../bus/platform
supplier:platform:ff420010.pwm -> ../../virtual/devlink/platform:ff420010.pwm--platform:p6-fan


I build this kernel with armbian default kernel config. How can we have different trees in /sys on same hardware?

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I confirm that I have the same issue, on kernel 5.18.0 with the default armbian build the fans are not detected by the hwmon module:

# uname
Linux helios64 5.18.0-rockchip64 #22.05.1 SMP PREEMPT Sat May 28 08:41:43 UTC 2022 aarch64 aarch64 aarch64 GNU/Linux
# dmesg | grep hwmon
[    8.480887] hwmon hwmon2: temp1_input not attached to any thermal zone
[    8.480906] lm75 2-004c: hwmon2: sensor 'lm75'
# # ll /sys/class/hwmon
total 0
lrwxrwxrwx 1 root root 0 Jun  5 18:47 hwmon0 -> ../../devices/virtual/thermal/thermal_zone0/hwmon0
lrwxrwxrwx 1 root root 0 Jun  5 18:47 hwmon1 -> ../../devices/virtual/thermal/thermal_zone1/hwmon1
lrwxrwxrwx 1 root root 0 Jun  5 18:47 hwmon2 -> ../../devices/platform/ff120000.i2c/i2c-2/2-004c/hwmon/hwmon2
lrwxrwxrwx 1 root root 0 Jun  5 18:47 hwmon3 -> ../../devices/platform/ff3d0000.i2c/i2c-4/4-0022/power_supply/tcpm-source-psy-4-0022/hwmon3
lrwxrwxrwx 1 root root 0 Jun  5 18:47 hwmon4 -> ../../devices/platform/gpio-charger/power_supply/gpio-charger/hwmon4

On kernel 5.17 it was working fine. Now digging into what could have caused this...

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