Thinkfan-Ex v1.2

Fan control rebuilt around measured hardware behaviour rather than assumed
behaviour, plus two new tools for measuring your own machine.

Highlights

Defaults derived from measurement. Fan speeds were benched on a repasted
ThinkPad T480 and the level ladder pruned to the speeds that actually differ.
Levels 4 and 7 measured identical to 3 and 6, and level 0 stops the fan entirely,
so all three are now unused. CRITICAL_TEMP is 88000 and HYSTERESIS 6000 to suit
the wider bands that pruning produces.

thinkfan-ex -check reports whether a machine supports fan control at all:
driver, fan interface, manual control state, which of level / auto /
disengaged / full-speed the firmware accepts, watchdog availability and sensor
count. Never touches the fan.

thinkfan-ex -probe measures real RPM at every level, waiting for the
tachometer to go steady rather than using a fixed dwell.

fanbench.sh is an interactive bench: live RPM, change level by keypress, and a
min/max/last table per level as you work through them.

EC watchdog armed automatically. If the daemon is killed without running its
cleanup trap, firmware reclaims the fan after WATCHDOG_TIMEOUT seconds.

Fixed

• An empty sensor read aborted the control loop under set -e. Some hwmon nodes
  return nothing while cat still exits 0, so the || echo 0 fallback never fired.
• Reading /sys/module/thinkpad_acpi/parameters/fan_control aborted the installer
  when thinkpad_acpi is built into the kernel rather than loaded as a module.
• The default fan command was auto, which /proc/acpi/ibm/fan rejects. The valid
  command is level auto.
• A grep miss while reading the current level aborted the loop under set -e.
• local error_code=$? always captured 0, because local resets $?.
• systemctl enable --now will not restart an already-running service, so
  reinstalling over a live install left the old daemon running the old code.
• Hysteresis was applied as an offset to every level below the current one, which
  shifts the whole ladder down while leaving the bands exactly as narrow as before.
  It is now a deadband around the level actually held.
• A single-sample temperature spike raised the level while the smoothed temperature
  still permitted an immediate drop, so the fan reversed itself one poll later.
  UP_CONFIRM requires consecutive readings to agree before raising.
• The configuration used when the config file fails its syntax check no longer
  diverges from the shipped defaults.

Added

• HYSTERESIS, SMOOTH_SAMPLES, UP_CONFIRM, WATCHDOG_TIMEOUT
• -check, -probe, fanbench.sh
• Startup logging of the configuration source and every resolved value

Upgrading

The installer does not overwrite an existing configuration, so a v1.1 config will
survive and silently keep the old curve. To take the new defaults:

sudo thinkfan-ex -uninstall
echo "level auto" | sudo tee /proc/acpi/ibm/fan
sudo rm -f /etc/thinkfan-extreme.conf
chmod +x thinkfan-extreme.sh
sudo ./thinkfan-extreme.sh

Note on the defaults

These thresholds were measured on one machine with healthy thermals. A laptop with
degraded paste will sit at the top of this curve constantly. Run -check, then
fanbench.sh, and set your thresholds against what your own fan does.