Lunar 2-in-1 Mini PC EC Driver

Overview

This is a Linux kernel HWMON driver for the Lunar 2-in-1 Mini PC, providing:

• Fan speed monitoring and control
• LED control for keyboard indicators (L1 and L2)

Building & Installing

make clean
make
sudo make install

Using DKMS

To install:

sudo make dkms

To remove:

sudo make dkms_clean

Notes:

• The module does not provide a real version number, so git describe --long is used to create one. This means that anything that changes the git state will change the version. make dkms_clean should be run before making a commit or an update with git pull as the Makefile is currently unable to track the last installed version to replace it. If this doesn't happen, the old version will need to be manually removed from dkms, before installing the updated module. Something like dkms remove -m lunar -v <old version> --all, followed by rm -rf /usr/src/lunar-<old version>, should do. dkms status -m lunar can be used to list the installed versions.

Features

• Read fan RPM via EC register values
• Control fan speed in automatic/manual modes
• Expose fan control and telemetry via hwmon interface
• LED brightness control for keyboard indicators through leds subsystem

Architecture

The driver communicates with the EC using LPC IO ports:

• Configuration addresses at 0x4E (address) and 0x4F (data)
• Addressing EC RAM using custom protocols via D2ADR/D2DAT IO ports

Modules

EC RAM I/O

Handles low-level read/write to EC RAM using mutex-protected access:

• ec_ram_read(uint16_t address)
• ec_ram_write(uint16_t address, uint8_t data)

Fan Control

• Data exposed via hwmon and thermal_cooling_device APIs

• PWM values scaled between EC range (0-184) and hwmon (0-200)

• Supports three modes:

  • Off
  • Manual (user-defined PWM)
  • Auto (firmware-controlled)

LED Control

• Two LEDs (L1 and L2) controlled by writing to EC
• State maintained in memory due to lack of readable EC brightness register

Interfaces

HWMON sysfs

Exposes the following attributes:

• /sys/class/hwmon/hwmonX/fan1_input – current fan speed (RPM)

• /sys/class/hwmon/hwmonX/pwm1 – fan speed setting (0-255)

• /sys/class/hwmon/hwmonX/pwm1_enable – fan mode:

  • 0 = Off (control off, speed 100%)
  • 1 = Manual
  • 2 = Automatic

LED sysfs

Exposes standard LED class entries:

• /sys/class/leds/L1/brightness - (0 off, 1-255 on)
• /sys/class/leds/L2/brightness - (0 off, 1-255 on)

DMI Match Table

Ensures driver only loads on supported hardware:

static const struct dmi_system_id lunar_dmi_table[] __initconst = {
    LUNAR_DMI_MATCH_VND("SU", "ARB33P"),
    { }
};

Register Map

Register	Address (hex)	Description
PNPCFG_ADDR	0x4E	EC address port
PNPCFG_DATA	0x4F	EC data port
D2ADR	0x2E	EC indirect address register
D2DAT	0x2F	EC indirect data register
I2EC_ADDR_L	0x10	EC RAM address low byte
I2EC_ADDR_H	0x11	EC RAM address high byte
I2EC_DATA	0x12	EC RAM data access
FAN_TACHO_ADDR_H	0x0218	Fan speed high byte
FAN_TACHO_ADDR_L	0x0219	Fan speed low byte
FAN_PWM_ADDR	0x1809	PWM duty cycle
FAN_MODE_ADDR	0x0F02	Fan control mode
L1 LED Address	0x04A0	L1 keyboard LED control
L2 LED Address	0x04A1	L2 keyboard LED control

License

GPL-2.0-or-later

Author

Rafal Goslawski rafal.goslawski@gmail.com