PWM write test for Pankha fan-control

pankha-pwm-test.sh

#!/usr/bin/env bash
#
set -u

HW="${1:-}"
N="${2:-}"
TARGET_PWM="${TARGET_PWM:-200}"
WATCH_SECS="${WATCH_SECS:-30}"

# --- Fan selection -------------------------------------------------------
# Both args supplied -> use directly. Otherwise list PWM-capable fans and let
# the user pick one (requires an interactive terminal).
if [ -z "$HW" ] || [ -z "$N" ]; then
  if [ ! -t 0 ]; then
    echo "No fan specified and not running interactively." >&2
    echo "Usage: sudo $0 <hwmon_path> <fan_number>" >&2
    exit 1
  fi

  echo "=== Available PWM-capable fans ==="
  echo "Pick a CHASSIS fan (rpm>0, writable=yes). Avoid the CPU cooler or an AIO pump header."
  echo
  declare -a SEL_HW SEL_N
  idx=0
  for h in /sys/class/hwmon/hwmon*; do
    [ -e "$h" ] || continue
    name=$(cat "$h/name" 2>/dev/null)
    for f in "$h"/fan[0-9]*_input; do
      [ -e "$f" ] || continue
      n=$(basename "$f" | sed 's/fan//; s/_input//')
      pp="$h/pwm${n}"
      [ -e "$pp" ] || continue
      idx=$((idx + 1))
      SEL_HW[$idx]="$h"
      SEL_N[$idx]="$n"
      printf '  [%2d] %-10s %s fan%s  rpm=%-6s pwm=%-4s enable=%-3s writable=%s\n' \
        "$idx" "$name" "$h" "$n" \
        "$(cat "$f" 2>/dev/null)" \
        "$(cat "$pp" 2>/dev/null)" \
        "$(cat "$h/pwm${n}_enable" 2>/dev/null || echo -)" \
        "$( [ -w "$pp" ] && echo yes || echo no )"
    done
  done

  if [ "$idx" -eq 0 ]; then
    echo "No PWM-capable fans found under /sys/class/hwmon." >&2
    echo "Is the it87 (or relevant Super I/O) driver loaded? See pankha-fan-diag.sh." >&2
    exit 1
  fi

  echo
  read -rp "Select fan number [1-$idx] (or q to quit): " choice
  case "$choice" in
    q|Q) echo "Aborted."; exit 0 ;;
    ''|*[!0-9]*) echo "Invalid selection." >&2; exit 1 ;;
  esac
  if [ "$choice" -lt 1 ] || [ "$choice" -gt "$idx" ]; then
    echo "Selection out of range." >&2
    exit 1
  fi
  HW="${SEL_HW[$choice]}"
  N="${SEL_N[$choice]}"
  echo
fi

PWM="$HW/pwm$N"
EN="$HW/pwm${N}_enable"
RPM="$HW/fan${N}_input"

if [ ! -w "$PWM" ]; then
  echo "ERROR: cannot write $PWM (run as root? wrong path/fan number?)" >&2
  exit 1
fi

# Final confirmation when interactive.
if [ -t 0 ]; then
  echo "Selected  : $(cat "$HW/name" 2>/dev/null) fan$N  ($PWM)"
  echo "This will raise it to pwm=$TARGET_PWM for ${WATCH_SECS}s, then restore the original value."
  read -rp "Proceed? [y/N]: " ok
  case "$ok" in
    y|Y|yes|YES) ;;
    *) echo "Aborted."; exit 0 ;;
  esac
  echo
fi

orig_pwm="$(cat "$PWM")"
orig_en="$(cat "$EN" 2>/dev/null || echo n/a)"
echo "Chip      : $(cat "$HW/name" 2>/dev/null)  ($HW)"
echo "BASELINE  : pwm=$orig_pwm enable=$orig_en rpm=$(cat "$RPM" 2>/dev/null)"

restore() {
  [ "$orig_en" != "n/a" ] && echo "$orig_en" > "$EN" 2>/dev/null
  echo "$orig_pwm" > "$PWM" 2>/dev/null
  echo "RESTORED  : pwm=$(cat "$PWM" 2>/dev/null) enable=$(cat "$EN" 2>/dev/null) rpm=$(cat "$RPM" 2>/dev/null)"
}
trap restore EXIT

# Enable manual PWM mode.
echo 1 > "$EN" 2>/dev/null
echo "After enable=1, reads back: $(cat "$EN" 2>/dev/null)  (if this is not 1, the chip refused manual mode)"

echo "Writing pwm=$TARGET_PWM and watching ${WATCH_SECS}s:"
echo "$TARGET_PWM" > "$PWM"
for i in $(seq 0 "$WATCH_SECS"); do
  printf '  t=%2ss  pwm=%-3s  enable=%-2s  rpm=%s\n' \
    "$i" "$(cat "$PWM" 2>/dev/null)" "$(cat "$EN" 2>/dev/null)" "$(cat "$RPM" 2>/dev/null)"
  sleep 1
done

echo "Watch complete. Interpretation:"
echo "  - pwm stayed $TARGET_PWM and rpm rose/held -> writes HOLD (control works)"
echo "  - pwm/rpm dropped back on their own        -> BIOS/SMM re-assert (timed override)"
echo "  - enable would not stay 1, or rpm flat     -> driver won't enter manual mode"
echo "Trap now restores original values."