Legion Performance Controller

Extreme Cooling (fans at maximum) and hardware monitoring for the Lenovo Legion Y720 on Linux.

Tested on: Legion Y720 (BIOS 4GCN, i7-7700HQ + GTX 1060), CachyOS. Other Y520/Y720-era Legions with the same EC layout may work, but are not a goal of this project.

CPU/GPU performance profiles are intentionally left to the system (power-profiles-daemon, tuned, KDE power settings).

---

Architecture

┌──────────────────────┐   system D-Bus    ┌───────────────────────────┐
│ legion-perf (GUI)    │ ────────────────▶ │ legion-perfd (root)       │
│ tray + window        │  io.github.       │  polkit check per call    │
│ runs as your user    │  bulbashenko.     │  restores state on resume │
│ reads /proc, /sys    │  LegionPerf       │                           │
└──────────────────────┘                   └──────┬────────────────────┘
                                                  │
                                          ec_sys (EC register 0xBD)

• legion-perfd — a small systemd service and the only privileged part. It exposes a D-Bus API and checks every change with polkit (io.github.bulbashenko.LegionPerf.configure). The active local session needs no password; remote and inactive sessions need admin authentication. Reading state is open to everyone.
• legion-perf — unprivileged Qt tray app. It shows the CPU temperature in the tray icon (green < 70 °C, yellow < 85 °C, red above; a blue frame means Extreme Cooling is on). It always starts in the tray only; clicking the icon (or launching it again from the menu) opens the window with CPU/RAM/iGPU/NVIDIA metrics and the Extreme Cooling switch.
• State: Extreme Cooling set through the daemon is re-applied after resume from suspend. After a reboot nothing is touched: the firmware defaults apply, so Extreme Cooling starts off.

Why Extreme Cooling goes through ec_sys

On Windows this is the WMI method SetFanCooling on LENOVO_GAMEZONE_DATA. On Linux no driver implements it for the Y720:

• the mainline lenovo-wmi-gamezone driver only supports SmartFan-capable (2020+) firmware and fails to probe on the Y720;
• LenovoLegionLinux calls a WMI GUID that the Y720 does not have.

ec_sys is the least invasive working option. It writes through the kernel's ACPI EC driver with its locking, unlike raw /dev/port I/O, and uses the same register and values as LenovoLegionLinux (EXT_MAXIMUMFANSPEED).

The proper long-term fix would be pwm1_enable support in lenovo-wmi-gamezone backed by SetFanCooling. The daemon keeps hardware access behind a small Control interface (src/legion_perf/hardware.py), so such a backend can replace ec_sys without touching anything else.

---

Not supported: fan_mode and camera_power

ideapad_laptop exposes both attributes on the Y720, but the firmware ignores writes and always reads back 0 (verified on BIOS 4GCN38WW). The driver creates them whenever the firmware answers the read command, so their presence in sysfs does not mean they work.

---

Installation (Arch / CachyOS)

cd packaging/arch
makepkg -si
sudo systemctl enable --now legion-perfd

The package builds from the committed HEAD of this repository. It installs:

Path	Purpose
/usr/bin/legion-perfd, /usr/bin/legion-perf	daemon and GUI
/usr/lib/systemd/system/legion-perfd.service	hardened systemd unit
/usr/share/dbus-1/system.d/…, system-services/…	D-Bus policy and activation
/usr/share/polkit-1/actions/io.github.bulbashenko.LegionPerf.policy	polkit action
/usr/lib/modules-load.d/legion-perf.conf, /usr/lib/modprobe.d/legion-perf.conf	load ec_sys with write_support=1 at boot
/etc/xdg/autostart/legion-perf.desktop	start the GUI in the tray on login

Remove with sudo pacman -R legion-perf.

Migrating from v1 (legion_perf.py)

sudo rm -f /usr/local/bin/legion-perf-helper /etc/polkit-1/actions/io.github.legion.perf.policy
rm -f ~/.local/bin/legion-perf ~/.local/share/applications/legion-perf.desktop \
      ~/.config/autostart/legion-perf.desktop

---

D-Bus API

Bus name and interface io.github.bulbashenko.LegionPerf, object /io/github/bulbashenko/LegionPerf.

Member	Type
Features	property as	extreme-cooling when ec_sys is available
ExtremeCooling	property b
Version	property s
SetExtremeCooling(b)	method	polkit-checked

Changes emit org.freedesktop.DBus.Properties.PropertiesChanged. From the shell:

busctl get-property io.github.bulbashenko.LegionPerf /io/github/bulbashenko/LegionPerf \
  io.github.bulbashenko.LegionPerf ExtremeCooling
busctl call io.github.bulbashenko.LegionPerf /io/github/bulbashenko/LegionPerf \
  io.github.bulbashenko.LegionPerf SetExtremeCooling b true

Errors: ….Error.NotAuthorized, ….Error.NotSupported, ….Error.Hardware.

---

Development

python -m venv --system-site-packages .venv   # PySide6 from the system package
.venv/bin/pip install -e ".[gui,dev]"

.venv/bin/ruff check src tests && .venv/bin/ruff format --check src tests
.venv/bin/mypy
.venv/bin/pytest

The tests never touch real hardware. The daemon runs against a fake sysfs/debugfs tree on a private dbus-daemon, with polkit replaced by a test authorizer, and the GUI client is tested against that daemon in a subprocess. CI runs the same checks on GitHub Actions.

To run the daemon by hand without root, on the session bus and without polkit:

.venv/bin/legion-perfd --session --root /path/to/fake/root -v

---

Troubleshooting

Window says "Daemon is not available" — systemctl status legion-perfd and journalctl -u legion-perfd.

Extreme Cooling switch is missing — ec_sys is not loaded with write support. Check that cat /sys/module/ec_sys/parameters/write_support prints Y, and that /sys/kernel/security/lockdown shows [none] (kernel lockdown blocks debugfs writes).

NVIDIA row shows "suspended (D3)" — the dGPU is runtime-suspended and is deliberately not polled, because nvidia-smi would wake it. Pascal cards such as the GTX 1060 do not support runtime D3, so on the Y720 the row always shows live data.

---

License

GPL-3.0 — see LICENSE. The v1 single-file version is kept in the v1 branch.