My system doesn't reacts at writing values below 255 to /sys/class/hwmon/hwmon0/device/pwm(2,3) which correspond to 3-wire case fans connected via M/B (ga-890gpa-ud3h) headers. The idea was taken from http://www.thinkwiki.org/wiki/How_to_control_fan_speed
ls /sys/class/hwmon/hwmon0/device/ alarms fan1_min fan3_beep fan5_min in0_min in2_alarm in3_beep in4_beep in5_input in6_max in7_max power/ pwm2_auto_channels_temp pwm3_freq temp1_min temp2_min temp3_min cpu0_vid fan2_alarm fan3_input hwmon/ in1_alarm in2_beep in3_input in4_input in5_max in6_min in7_min pwm1 pwm2_enable subsystem@ temp1_type temp2_type temp3_type driver@ fan2_beep fan3_min in0_alarm in1_beep in2_input in3_label in4_max in5_min in7_alarm in8_input pwm1_auto_channels_temp pwm2_freq temp1_alarm temp2_alarm temp3_alarm uevent fan1_alarm fan2_input fan5_alarm in0_beep in1_input in2_max in3_max in4_min in6_alarm in7_beep in8_label pwm1_enable pwm3 temp1_beep temp2_beep temp3_beep vrm fan1_beep fan2_min fan5_beep in0_input in1_max in2_min in3_min in5_alarm in6_beep in7_input modalias pwm1_freq pwm3_auto_channels_temp temp1_input temp2_input temp3_input fan1_input fan3_alarm fan5_input in0_max in1_min in3_alarm in4_alarm in5_beep in6_input in7_label name pwm2 pwm3_enable temp1_max temp2_max temp3_max
It indeed shows the actual speed:
cat /sys/class/hwmon/hwmon0/device/fan5_input 5769
But refuses to write to fanX_input: permission denied (even for root).
More specs: kernel 18.104.22.168,
sensors output is:
it8720-isa-0228 Adapter: ISA adapter
I do not run any daemons for fan control, but suppose the speed may be set by CPU in-kernel governor. How to stop a fan under this conditions without doing hardware tricks?
Upd: part of pwmconfig's output:
Found the following devices: hwmon0/device is it8720 hwmon1/device is k10temp Found the following PWM controls: hwmon0/device/pwm1 hwmon0/device/pwm2 hwmon0/device/pwm2 is currently setup for automatic speed control. In general, automatic mode is preferred over manual mode, as it is more efficient and it reacts faster. Are you sure that you want to setup this output for manual control? (n) y hwmon0/device/pwm3 hwmon0/device/pwm3 is currently setup for automatic speed control. In general, automatic mode is preferred over manual mode, as it is more efficient and it reacts faster. Are you sure that you want to setup this output for manual control? (n) y
Warning!!! This program will stop your fans, one at a time, for approximately 5 seconds each!!! This may cause your processor temperature to rise!!! If you do not want to do this hit control-C now!!! Hit return to continue: Testing pwm control hwmon0/device/pwm1 ... hwmon0/device/fan1_input ... speed was 4326 now 2136 It appears that fan hwmon0/device/fan1_input is controlled by pwm hwmon0/device/pwm1 Would you like to generate a detailed correlation (y)? y
This was stopping CPU fan. And:
hwmon0/device/fan3_input ... speed was 1997 now 1997 no correlation hwmon0/device/fan5_input ... speed was 5720 now 5720 no correlation Testing pwm control hwmon0/device/pwm2 ... hwmon0/device/fan1_input ... speed was 4326 now 4383 no correlation hwmon0/device/fan3_input ... speed was 1997 now 1997 no correlation hwmon0/device/fan5_input ... speed was 5720 now 5720 no correlation No correlations