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diff --git a/Documentation/wmi/devices/msi-wmi-platform.rst b/Documentation/wmi/devices/msi-wmi-platform.rst new file mode 100644 index 000000000000..29b1b2e6d42c --- /dev/null +++ b/Documentation/wmi/devices/msi-wmi-platform.rst @@ -0,0 +1,194 @@ +.. SPDX-License-Identifier: GPL-2.0-or-later + +=================================================== +MSI WMI Platform Features driver (msi-wmi-platform) +=================================================== + +Introduction +============ + +Many MSI notebooks support various features like reading fan sensors. This features are controlled +by the embedded controller, with the ACPI firmware exposing a standard ACPI WMI interface on top +of the embedded controller interface. + +WMI interface description +========================= + +The WMI interface description can be decoded from the embedded binary MOF (bmof) +data using the `bmfdec <https://github.com/pali/bmfdec>`_ utility: + +:: + + [WMI, Locale("MS\0x409"), + Description("This class contains the definition of the package used in other classes"), + guid("{ABBC0F60-8EA1-11d1-00A0-C90629100000}")] + class Package { + [WmiDataId(1), read, write, Description("16 bytes of data")] uint8 Bytes[16]; + }; + + [WMI, Locale("MS\0x409"), + Description("This class contains the definition of the package used in other classes"), + guid("{ABBC0F63-8EA1-11d1-00A0-C90629100000}")] + class Package_32 { + [WmiDataId(1), read, write, Description("32 bytes of data")] uint8 Bytes[32]; + }; + + [WMI, Dynamic, Provider("WmiProv"), Locale("MS\0x409"), + Description("Class used to operate methods on a package"), + guid("{ABBC0F6E-8EA1-11d1-00A0-C90629100000}")] + class MSI_ACPI { + [key, read] string InstanceName; + [read] boolean Active; + + [WmiMethodId(1), Implemented, read, write, Description("Return the contents of a package")] + void GetPackage([out, id(0)] Package Data); + + [WmiMethodId(2), Implemented, read, write, Description("Set the contents of a package")] + void SetPackage([in, id(0)] Package Data); + + [WmiMethodId(3), Implemented, read, write, Description("Return the contents of a package")] + void Get_EC([out, id(0)] Package_32 Data); + + [WmiMethodId(4), Implemented, read, write, Description("Set the contents of a package")] + void Set_EC([in, id(0)] Package_32 Data); + + [WmiMethodId(5), Implemented, read, write, Description("Return the contents of a package")] + void Get_BIOS([in, out, id(0)] Package_32 Data); + + [WmiMethodId(6), Implemented, read, write, Description("Set the contents of a package")] + void Set_BIOS([in, out, id(0)] Package_32 Data); + + [WmiMethodId(7), Implemented, read, write, Description("Return the contents of a package")] + void Get_SMBUS([in, out, id(0)] Package_32 Data); + + [WmiMethodId(8), Implemented, read, write, Description("Set the contents of a package")] + void Set_SMBUS([in, out, id(0)] Package_32 Data); + + [WmiMethodId(9), Implemented, read, write, Description("Return the contents of a package")] + void Get_MasterBattery([in, out, id(0)] Package_32 Data); + + [WmiMethodId(10), Implemented, read, write, Description("Set the contents of a package")] + void Set_MasterBattery([in, out, id(0)] Package_32 Data); + + [WmiMethodId(11), Implemented, read, write, Description("Return the contents of a package")] + void Get_SlaveBattery([in, out, id(0)] Package_32 Data); + + [WmiMethodId(12), Implemented, read, write, Description("Set the contents of a package")] + void Set_SlaveBattery([in, out, id(0)] Package_32 Data); + + [WmiMethodId(13), Implemented, read, write, Description("Return the contents of a package")] + void Get_Temperature([in, out, id(0)] Package_32 Data); + + [WmiMethodId(14), Implemented, read, write, Description("Set the contents of a package")] + void Set_Temperature([in, out, id(0)] Package_32 Data); + + [WmiMethodId(15), Implemented, read, write, Description("Return the contents of a package")] + void Get_Thermal([in, out, id(0)] Package_32 Data); + + [WmiMethodId(16), Implemented, read, write, Description("Set the contents of a package")] + void Set_Thermal([in, out, id(0)] Package_32 Data); + + [WmiMethodId(17), Implemented, read, write, Description("Return the contents of a package")] + void Get_Fan([in, out, id(0)] Package_32 Data); + + [WmiMethodId(18), Implemented, read, write, Description("Set the contents of a package")] + void Set_Fan([in, out, id(0)] Package_32 Data); + + [WmiMethodId(19), Implemented, read, write, Description("Return the contents of a package")] + void Get_Device([in, out, id(0)] Package_32 Data); + + [WmiMethodId(20), Implemented, read, write, Description("Set the contents of a package")] + void Set_Device([in, out, id(0)] Package_32 Data); + + [WmiMethodId(21), Implemented, read, write, Description("Return the contents of a package")] + void Get_Power([in, out, id(0)] Package_32 Data); + + [WmiMethodId(22), Implemented, read, write, Description("Set the contents of a package")] + void Set_Power([in, out, id(0)] Package_32 Data); + + [WmiMethodId(23), Implemented, read, write, Description("Return the contents of a package")] + void Get_Debug([in, out, id(0)] Package_32 Data); + + [WmiMethodId(24), Implemented, read, write, Description("Set the contents of a package")] + void Set_Debug([in, out, id(0)] Package_32 Data); + + [WmiMethodId(25), Implemented, read, write, Description("Return the contents of a package")] + void Get_AP([in, out, id(0)] Package_32 Data); + + [WmiMethodId(26), Implemented, read, write, Description("Set the contents of a package")] + void Set_AP([in, out, id(0)] Package_32 Data); + + [WmiMethodId(27), Implemented, read, write, Description("Return the contents of a package")] + void Get_Data([in, out, id(0)] Package_32 Data); + + [WmiMethodId(28), Implemented, read, write, Description("Set the contents of a package")] + void Set_Data([in, out, id(0)] Package_32 Data); + + [WmiMethodId(29), Implemented, read, write, Description("Return the contents of a package")] + void Get_WMI([out, id(0)] Package_32 Data); + }; + +Due to a peculiarity in how Windows handles the ``CreateByteField()`` ACPI operator (errors only +happen when a invalid byte field is ultimately accessed), all methods require a 32 byte input +buffer, even if the Binay MOF says otherwise. + +The input buffer contains a single byte to select the subfeature to be accessed and 31 bytes of +input data, the meaning of which depends on the subfeature being accessed. + +The output buffer contains a singe byte which signals success or failure (``0x00`` on failure) +and 31 bytes of output data, the meaning if which depends on the subfeature being accessed. + +WMI method Get_EC() +------------------- + +Returns embedded controller information, the selected subfeature does not matter. The output +data contains a flag byte and a 28 byte controller firmware version string. + +The first 4 bits of the flag byte contain the minor version of the embedded controller interface, +with the next 2 bits containing the major version of the embedded controller interface. + +The 7th bit signals if the embedded controller page chaged (exact meaning is unknown), and the +last bit signals if the platform is a Tigerlake platform. + +The MSI software seems to only use this interface when the last bit is set. + +WMI method Get_Fan() +-------------------- + +Fan speed sensors can be accessed by selecting subfeature ``0x00``. The output data contains +up to four 16-bit fan speed readings in big-endian format. Most machines do not support all +four fan speed sensors, so the remaining reading are hardcoded to ``0x0000``. + +The fan RPM readings can be calculated with the following formula: + + RPM = 480000 / <fan speed reading> + +If the fan speed reading is zero, then the fan RPM is zero too. + +WMI method Get_WMI() +-------------------- + +Returns the version of the ACPI WMI interface, the selected subfeature does not matter. +The output data contains two bytes, the first one contains the major version and the last one +contains the minor revision of the ACPI WMI interface. + +The MSI software seems to only use this interface when the major version is greater than two. + +Reverse-Engineering the MSI WMI Platform interface +================================================== + +.. warning:: Randomly poking the embedded controller interface can potentially cause damage + to the machine and other unwanted side effects, please be careful. + +The underlying embedded controller interface is used by the ``msi-ec`` driver, and it seems +that many methods just copy a part of the embedded controller memory into the output buffer. + +This means that the remaining WMI methods can be reverse-engineered by looking which part of +the embedded controller memory is accessed by the ACPI AML code. The driver also supports a +debugfs interface for directly executing WMI methods. Additionally, any safety checks regarding +unsupported hardware can be disabled by loading the module with ``force=true``. + +More information about the MSI embedded controller interface can be found at the +`msi-ec project <https://github.com/BeardOverflow/msi-ec>`_. + +Special thanks go to github user `glpnk` for showing how to decode the fan speed readings. |