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diff --git a/Documentation/wmi/devices/dell-wmi-ddv.rst b/Documentation/wmi/devices/dell-wmi-ddv.rst new file mode 100644 index 0000000000..2fcdfcf033 --- /dev/null +++ b/Documentation/wmi/devices/dell-wmi-ddv.rst @@ -0,0 +1,297 @@ +.. SPDX-License-Identifier: GPL-2.0-or-later + +============================================ +Dell DDV WMI interface driver (dell-wmi-ddv) +============================================ + +Introduction +============ + +Many Dell notebooks made after ~2020 support a WMI-based interface for +retrieving various system data like battery temperature, ePPID, diagostic data +and fan/thermal sensor data. + +This interface is likely used by the `Dell Data Vault` software on Windows, +so it was called `DDV`. Currently the ``dell-wmi-ddv`` driver supports +version 2 and 3 of the interface, with support for new interface versions +easily added. + +.. warning:: The interface is regarded as internal by Dell, so no vendor + documentation is available. All knowledge was thus obtained by + trial-and-error, please keep that in mind. + +Dell ePPID (electronic Piece Part Identification) +================================================= + +The Dell ePPID is used to uniquely identify components in Dell machines, +including batteries. It has a form similar to `CC-PPPPPP-MMMMM-YMD-SSSS-FFF` +and contains the following information: + +* Country code of origin (CC). +* Part number with the first character being a filling number (PPPPPP). +* Manufacture Identification (MMMMM). +* Manufacturing Year/Month/Date (YMD) in base 36, with Y being the last digit + of the year. +* Manufacture Sequence Number (SSSS). +* Optional Firmware Version/Revision (FFF). + +The `eppidtool <https://pypi.org/project/eppidtool>`_ python utility can be used +to decode and display this information. + +All information regarding the Dell ePPID was gathered using Dell support +documentation and `this website <https://telcontar.net/KBK/Dell/date_codes>`_. + +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, Dynamic, Provider("WmiProv"), Locale("MS\\0x409"), Description("WMI Function"), guid("{8A42EA14-4F2A-FD45-6422-0087F7A7E608}")] + class DDVWmiMethodFunction { + [key, read] string InstanceName; + [read] boolean Active; + + [WmiMethodId(1), Implemented, read, write, Description("Return Battery Design Capacity.")] void BatteryDesignCapacity([in] uint32 arg2, [out] uint32 argr); + [WmiMethodId(2), Implemented, read, write, Description("Return Battery Full Charge Capacity.")] void BatteryFullChargeCapacity([in] uint32 arg2, [out] uint32 argr); + [WmiMethodId(3), Implemented, read, write, Description("Return Battery Manufacture Name.")] void BatteryManufactureName([in] uint32 arg2, [out] string argr); + [WmiMethodId(4), Implemented, read, write, Description("Return Battery Manufacture Date.")] void BatteryManufactureDate([in] uint32 arg2, [out] uint32 argr); + [WmiMethodId(5), Implemented, read, write, Description("Return Battery Serial Number.")] void BatterySerialNumber([in] uint32 arg2, [out] uint32 argr); + [WmiMethodId(6), Implemented, read, write, Description("Return Battery Chemistry Value.")] void BatteryChemistryValue([in] uint32 arg2, [out] string argr); + [WmiMethodId(7), Implemented, read, write, Description("Return Battery Temperature.")] void BatteryTemperature([in] uint32 arg2, [out] uint32 argr); + [WmiMethodId(8), Implemented, read, write, Description("Return Battery Current.")] void BatteryCurrent([in] uint32 arg2, [out] uint32 argr); + [WmiMethodId(9), Implemented, read, write, Description("Return Battery Voltage.")] void BatteryVoltage([in] uint32 arg2, [out] uint32 argr); + [WmiMethodId(10), Implemented, read, write, Description("Return Battery Manufacture Access(MA code).")] void BatteryManufactureAceess([in] uint32 arg2, [out] uint32 argr); + [WmiMethodId(11), Implemented, read, write, Description("Return Battery Relative State-Of-Charge.")] void BatteryRelativeStateOfCharge([in] uint32 arg2, [out] uint32 argr); + [WmiMethodId(12), Implemented, read, write, Description("Return Battery Cycle Count")] void BatteryCycleCount([in] uint32 arg2, [out] uint32 argr); + [WmiMethodId(13), Implemented, read, write, Description("Return Battery ePPID")] void BatteryePPID([in] uint32 arg2, [out] string argr); + [WmiMethodId(14), Implemented, read, write, Description("Return Battery Raw Analytics Start")] void BatteryeRawAnalyticsStart([in] uint32 arg2, [out] uint32 argr); + [WmiMethodId(15), Implemented, read, write, Description("Return Battery Raw Analytics")] void BatteryeRawAnalytics([in] uint32 arg2, [out] uint32 RawSize, [out, WmiSizeIs("RawSize") : ToInstance] uint8 RawData[]); + [WmiMethodId(16), Implemented, read, write, Description("Return Battery Design Voltage.")] void BatteryDesignVoltage([in] uint32 arg2, [out] uint32 argr); + [WmiMethodId(17), Implemented, read, write, Description("Return Battery Raw Analytics A Block")] void BatteryeRawAnalyticsABlock([in] uint32 arg2, [out] uint32 RawSize, [out, WmiSizeIs("RawSize") : ToInstance] uint8 RawData[]); + [WmiMethodId(18), Implemented, read, write, Description("Return Version.")] void ReturnVersion([in] uint32 arg2, [out] uint32 argr); + [WmiMethodId(32), Implemented, read, write, Description("Return Fan Sensor Information")] void FanSensorInformation([in] uint32 arg2, [out] uint32 RawSize, [out, WmiSizeIs("RawSize") : ToInstance] uint8 RawData[]); + [WmiMethodId(34), Implemented, read, write, Description("Return Thermal Sensor Information")] void ThermalSensorInformation([in] uint32 arg2, [out] uint32 RawSize, [out, WmiSizeIs("RawSize") : ToInstance] uint8 RawData[]); + }; + +Each WMI method takes an ACPI buffer containing a 32-bit index as input argument, +with the first 8 bit being used to specify the battery when using battery-related +WMI methods. Other WMI methods may ignore this argument or interpret it +differently. The WMI method output format varies: + +* if the function has only a single output, then an ACPI object + of the corresponding type is returned +* if the function has multiple outputs, when an ACPI package + containing the outputs in the same order is returned + +The format of the output should be thoroughly checked, since many methods can +return malformed data in case of an error. + +The data format of many battery-related methods seems to be based on the +`Smart Battery Data Specification`, so unknown battery-related methods are +likely to follow this standard in some way. + +WMI method GetBatteryDesignCapacity() +------------------------------------- + +Returns the design capacity of the battery in mAh as an u16. + +WMI method BatteryFullCharge() +------------------------------ + +Returns the full charge capacity of the battery in mAh as an u16. + +WMI method BatteryManufactureName() +----------------------------------- + +Returns the manufacture name of the battery as an ASCII string. + +WMI method BatteryManufactureDate() +----------------------------------- + +Returns the manufacture date of the battery as an u16. +The date is encoded in the following manner: + +- bits 0 to 4 contain the manufacture day. +- bits 5 to 8 contain the manufacture month. +- bits 9 to 15 contain the manufacture year biased by 1980. + +.. note:: + The data format needs to be verified on more machines. + +WMI method BatterySerialNumber() +-------------------------------- + +Returns the serial number of the battery as an u16. + +WMI method BatteryChemistryValue() +---------------------------------- + +Returns the chemistry of the battery as an ASCII string. +Known values are: + +- "Li-I" for Li-Ion + +WMI method BatteryTemperature() +------------------------------- + +Returns the temperature of the battery in tenth degree kelvin as an u16. + +WMI method BatteryCurrent() +--------------------------- + +Returns the current flow of the battery in mA as an s16. +Negative values indicate discharging. + +WMI method BatteryVoltage() +--------------------------- + +Returns the voltage flow of the battery in mV as an u16. + +WMI method BatteryManufactureAccess() +------------------------------------- + +Returns a manufacture-defined value as an u16. + +WMI method BatteryRelativeStateOfCharge() +----------------------------------------- + +Returns the capacity of the battery in percent as an u16. + +WMI method BatteryCycleCount() +------------------------------ + +Returns the cycle count of the battery as an u16. + +WMI method BatteryePPID() +------------------------- + +Returns the ePPID of the battery as an ASCII string. + +WMI method BatteryeRawAnalyticsStart() +-------------------------------------- + +Performs an analysis of the battery and returns a status code: + +- ``0x0``: Success +- ``0x1``: Interface not supported +- ``0xfffffffe``: Error/Timeout + +.. note:: + The meaning of this method is still largely unknown. + +WMI method BatteryeRawAnalytics() +--------------------------------- + +Returns a buffer usually containing 12 blocks of analytics data. +Those blocks contain: + +- a block number starting with 0 (u8) +- 31 bytes of unknown data + +.. note:: + The meaning of this method is still largely unknown. + +WMI method BatteryDesignVoltage() +--------------------------------- + +Returns the design voltage of the battery in mV as an u16. + +WMI method BatteryeRawAnalyticsABlock() +--------------------------------------- + +Returns a single block of analytics data, with the second byte +of the index being used for selecting the block number. + +*Supported since WMI interface version 3!* + +.. note:: + The meaning of this method is still largely unknown. + +WMI method ReturnVersion() +-------------------------- + +Returns the WMI interface version as an u32. + +WMI method FanSensorInformation() +--------------------------------- + +Returns a buffer containing fan sensor entries, terminated +with a single ``0xff``. +Those entries contain: + +- fan type (u8) +- fan speed in RPM (little endian u16) + +WMI method ThermalSensorInformation() +------------------------------------- + +Returns a buffer containing thermal sensor entries, terminated +with a single ``0xff``. +Those entries contain: + +- thermal type (u8) +- current temperature (s8) +- min. temperature (s8) +- max. temperature (s8) +- unknown field (u8) + +.. note:: + TODO: Find out what the meaning of the last byte is. + +ACPI battery matching algorithm +=============================== + +The algorithm used to match ACPI batteries to indices is based on information +which was found inside the logging messages of the OEM software. + +Basically for each new ACPI battery, the serial numbers of the batteries behind +indices 1 till 3 are compared with the serial number of the ACPI battery. +Since the serial number of the ACPI battery can either be encoded as a normal +integer or as a hexadecimal value, both cases need to be checked. The first +index with a matching serial number is then selected. + +A serial number of 0 indicates that the corresponding index is not associated +with an actual battery, or that the associated battery is not present. + +Some machines like the Dell Inspiron 3505 only support a single battery and thus +ignore the battery index. Because of this the driver depends on the ACPI battery +hook mechanism to discover batteries. + +.. note:: + The ACPI battery matching algorithm currently used inside the driver is + outdated and does not match the algorithm described above. The reasons for + this are differences in the handling of the ToHexString() ACPI opcode between + Linux and Windows, which distorts the serial number of ACPI batteries on many + machines. Until this issue is resolved, the driver cannot use the above + algorithm. + +Reverse-Engineering the DDV WMI interface +========================================= + +1. Find a supported Dell notebook, usually made after ~2020. +2. Dump the ACPI tables and search for the WMI device (usually called "ADDV"). +3. Decode the corresponding bmof data and look at the ASL code. +4. Try to deduce the meaning of a certain WMI method by comparing the control + flow with other ACPI methods (_BIX or _BIF for battery related methods + for example). +5. Use the built-in UEFI diagostics to view sensor types/values for fan/thermal + related methods (sometimes overwriting static ACPI data fields can be used + to test different sensor type values, since on some machines this data is + not reinitialized upon a warm reset). + +Alternatively: + +1. Load the ``dell-wmi-ddv`` driver, use the ``force`` module param + if necessary. +2. Use the debugfs interface to access the raw fan/thermal sensor buffer data. +3. Compare the data with the built-in UEFI diagnostics. + +In case the DDV WMI interface version available on your Dell notebook is not +supported or you are seeing unknown fan/thermal sensors, please submit a +bugreport on `bugzilla <https://bugzilla.kernel.org>`_ so they can be added +to the ``dell-wmi-ddv`` driver. + +See Documentation/admin-guide/reporting-issues.rst for further information. |