Re: T420 fan and Ubuntu 25.04

Good day!

On Sat, Feb 07, 2026 at 02:08:05AM +0100, gregor herrmann wrote:
> > T420 + Ubuntu 24.04.2 LTS - I could write to /proc/acpi/ibm/fan
> > for fan control.
> > That worked.
> > 
> > T420 + Ubuntu 25.04 - Now I get:
> > 
> > ====================================
> > % cat fan_2.sh
> > echo "level 2" > /proc/acpi/ibm/fan
> > 
> > % sudo ./fan_2.sh
> > ./fan_2.sh: 1: echo: echo: I/O error
> > ====================================
> > 
> > Known issue (after upgrading)?
> 
> Do you still have something like
> 
> # cat /etc/modprobe.d/thinkpad_acpi.conf
> options thinkpad_acpi fan_control=1

Yes.

% cat /etc/modprobe.d/thinkpad_acpi.conf
options thinkpad_acpi fan_control=1

% sudo grep -i thinkpad /var/log/dmesg
                       BIOS vendor: LENOVO; Ver: 83ET76WW (1.46 ); Product Version: ThinkPad
T420
[    5.299925] kernel: thinkpad_acpi: ThinkPad ACPI Extras v0.26
[    5.300072] kernel: thinkpad_acpi: http://ibm-acpi.sf.net/
[    5.300122] kernel: thinkpad_acpi: ThinkPad BIOS 83ET76WW (1.46 ), EC unknown
[    5.300169] kernel: thinkpad_acpi: Lenovo ThinkPad T420, model 4180AH9
[    5.317030] kernel: thinkpad_acpi: radio switch found; radios are enabled
[    5.317139] kernel: thinkpad_acpi: This ThinkPad has standard ACPI backlight brightness control, supported by the ACPI video driver
[    5.317201] kernel: thinkpad_acpi: Disabling thinkpad-acpi brightness events by default...
[    5.354172] kernel: thinkpad_acpi: rfkill switch tpacpi_bluetooth_sw: radio is unblocked
[    5.355133] kernel: thinkpad_acpi: Standard ACPI backlight interface available, not loading native one
[    5.426089] kernel: thinkpad_acpi: battery 1 registered (start 0, stop 100, behaviours: 0x7)
[    5.439070] kernel: ACPI: battery: new hook: ThinkPad Battery Extension
[    5.466048] kernel: input: ThinkPad Extra Buttons as /devices/platform/thinkpad_acpi/input/input6

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-- http://www.yurichev.com
Here I acknowledge that emails I use(d) are indeed: https://yurichev.com/contact.html#list
Expecting a reply from me? Maybe your email was marked as spam.
Please resend it to dennis.yurichev at gmail.com and/or dennis at yurichev.(com|org|net)
My emails are also sometimes stuck in spam folder, so please check it...
Internet email is subject to wholesale government surveillance.
My PGP keys: http://yurichev.com/pgp.html
Current key is B34936C128544E50BBDB88F1BF015EC5556DC725
Created 2021-06-28, expires 2026-06-27

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