[Bug 1155107] [NEW] pwmconfig assumes no fan control from fans not stopping

[charonme]

Public bug reported:

pwmconfig attempts to stop fans to determine whether it's possible to
control fan speed.  If fans don't respond to the stopping signal,
pwmconfig assumes it's not possible to control the fans. However some
motherboards or BIOS configurations seem to protect the fans from
stopping, but it's still possible to set non-zero fan speeds. For
example after sudo su I was able to echo 20 >
/sys/class/hwmon/hwmon2/device/pwm1 which set a very slow fan speed and
echo 120 >  /sys/class/hwmon/hwmon2/device/pwm1 set a much higher speed
- so obviously fan speed is working perfectly at least in this range.
However if I try to set a very low value (between 0 and 17) the fan
speeds up probably as a result of the mainboard or BIOS protection.

pwmconfig should take into account that sometimes (on some mobos or
bioses) fan speed control is only possible in some range of speeds
and/or stopping the fans is not always possible even though fan control
works

** Affects: lm-sensors (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: fancontrol pwmconfig

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https://bugs.launchpad.net/bugs/1155107

Title:
  pwmconfig assumes no fan control from fans not stopping

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