asus-ec-sensors

Linux HWMON sensors driver for ASUS motherboards to read sensor data from the embedded controller

Many ASUS motherboards do not publish all the available sensors via the Super I/O chip but the missing ones are available through the embedded controller (EC) registers.

The EC registers do not provide critical values for the sensors and as such they are not published to the HWMON.

This driver is available in the mainline kernel since version 5.18, and code in this repository is kept in sync with the hwmon-next branch.

Supported motherboards

• PRIME X470-PRO
• PRIME X570-PRO
• Pro WS X570-ACE
• ProArt X570-CREATOR WIFI
• ProArt B550-CREATOR
• ROG CROSSHAIR VIII DARK HERO
• ROG CROSSHAIR VIII HERO (WI-FI)
• ROG CROSSHAIR VIII FORMULA
• ROG CROSSHAIR VIII HERO
• ROG CROSSHAIR VIII IMPACT
• ROG CROSSHAIR X670E HERO
• ROG MAXIMUS XI HERO
• ROG MAXIMUS XI HERO (WI-FI)
• ROG STRIX B550-E GAMING
• ROG STRIX B550-I GAMING
• ROG STRIX X570-E GAMING
• ROG STRIX X570-E GAMING WIFI II
• ROG STRIX X570-F GAMING
• ROG STRIX X570-I GAMING
• ROG STRIX X670E-E GAMING WIFI
• ROG STRIX Z390-F GAMING
• ROG STRIX Z690-A GAMING WIFI D4
• ROG ZENITH II EXTREME
• ROG ZENITH II EXTREME ALPHA

Installation

Gentoo ebuild and AUR package are available. Alternatively, you can clone the repository and then use standard make and make modules_install (as root) commands. If you use DKMS, make dkms will build the module and add it to the DKMS tree for future updates.

Adding a new motherboard

You can use other monitoring software to learn whether the motherboard provide sensor data via the EC. For example, HWiNFO64 shows node named "ASUS EC" for these sensors.

Libre Hardware Monitor contains a very similar to this driver implementation for EC sensors, you can look there or even test and implement support for your board with Libre Hardware Monitor first.

First, you need identification data for your board, which are vendor and board names. You can get them from DMI tables using either the dmidecode utility or run grep -e '' -n /sys/class/dmi/id/board_{name,vendor}. If the vendor name equals (case sensitively) to "ASUSTeK COMPUTER INC." you simply add a new entry to the dmi_table array (please keep it sorted alphabetically by board name) using the DMI_EXACT_MATCH_ASUS_BOARD_NAME macro. If the vendor name is different, please create a similar macro that accepts also the vendor name as a parameter.

The second step is to find out which sensors are supported and create a ec_board_info structure with sensor definitions for the board. You can get a hint from HWINFO if it supports your board, from the monitoring section of the UEFI user interface, or from information for similar boards. Please note differences in sensor addresses for various board families.

The last step is to find out how to secure access to the EC from race condition, because the firmware does access the same data. If you are lucky, the name of a ACPI mutex, which is used for synchronising access to the EC, can be found out in the decompiled code of the ACPI firmware.

First, you need to obtain ACPI DSDT source for your board. You can get it from /sys/firmware/acpi/tables/DSDT in the binary form and decompile using the iasl tool from the acpica package:

$ sudo cat /sys/firmware/acpi/tables/DSDT > dsdt.dat
$ iasl dsdt.dat

This will produce decompiled file dsdt.dsl which you need to read and gather some information from it. Now you are on your own. Look for the definition of the EC device (PNP0C09) and for ACPI methods which access its address space. For example, in the AMD 500 series, there is a function named BREC (probably "Block Read Embedded Controller"). Its declaration starts with Method (BREC, 1. If the function contains meaningful code, read through it a bit. Not far from the beginning it should contain a command to lock a mutex. The command in the AML (the language of the ACPI code) is named Acquire and the instructions should look like If ((Acquire (ASMX, 0xFFFF) == Zero)). You need the name of the mutex, here it is "ASMX". Now find its declaration (Mutex (ASMX, 0x00)). It will be declared inside a scope, with the scope declaration looking as Device (<Device name>), find the closest one to the mutex declaration towards the top of the file. Now compose the full name of the mutex, which starts from the '' and then consists of device name(s) and the mutex name. In the example above the name is \AMW0.ASMX. If you can't find mutex name, as the last resort you can use the global ACPI lock.

Now you can write down a definition for ec_board_info structure for your board, hook its address into the board identification array dmi_table, compile, and try to load the module (you might need to run make install in order to make the build system to sign the module, if your kernel rejects unsigned ones). Then the sensors command should show an entry named "asusec-..." with the sensor readings (sensors 'asusec-*' will show only that entry). Please note the blank value for temperature sensors: 216.