1.. SPDX-License-Identifier: GPL-2.0-or-later 2 3============================================ 4Dell DDV WMI interface driver (dell-wmi-ddv) 5============================================ 6 7Introduction 8============ 9 10Many Dell notebooks made after ~2020 support a WMI-based interface for 11retrieving various system data like battery temperature, ePPID, diagostic data 12and fan/thermal sensor data. 13 14This interface is likely used by the `Dell Data Vault` software on Windows, 15so it was called `DDV`. Currently the ``dell-wmi-ddv`` driver supports 16version 2 and 3 of the interface, with support for new interface versions 17easily added. 18 19.. warning:: The interface is regarded as internal by Dell, so no vendor 20 documentation is available. All knowledge was thus obtained by 21 trial-and-error, please keep that in mind. 22 23Dell ePPID (electronic Piece Part Identification) 24================================================= 25 26The Dell ePPID is used to uniquely identify components in Dell machines, 27including batteries. It has a form similar to `CC-PPPPPP-MMMMM-YMD-SSSS-FFF` 28and contains the following information: 29 30* Country code of origin (CC). 31* Part number with the first character being a filling number (PPPPPP). 32* Manufacture Identification (MMMMM). 33* Manufacturing Year/Month/Date (YMD) in base 36, with Y being the last digit 34 of the year. 35* Manufacture Sequence Number (SSSS). 36* Optional Firmware Version/Revision (FFF). 37 38The `eppidtool <https://pypi.org/project/eppidtool>`_ python utility can be used 39to decode and display this information. 40 41All information regarding the Dell ePPID was gathered using Dell support 42documentation and `this website <https://telcontar.net/KBK/Dell/date_codes>`_. 43 44WMI interface description 45========================= 46 47The WMI interface description can be decoded from the embedded binary MOF (bmof) 48data using the `bmfdec <https://github.com/pali/bmfdec>`_ utility: 49 50:: 51 52 [WMI, Dynamic, Provider("WmiProv"), Locale("MS\\0x409"), Description("WMI Function"), guid("{8A42EA14-4F2A-FD45-6422-0087F7A7E608}")] 53 class DDVWmiMethodFunction { 54 [key, read] string InstanceName; 55 [read] boolean Active; 56 57 [WmiMethodId(1), Implemented, read, write, Description("Return Battery Design Capacity.")] void BatteryDesignCapacity([in] uint32 arg2, [out] uint32 argr); 58 [WmiMethodId(2), Implemented, read, write, Description("Return Battery Full Charge Capacity.")] void BatteryFullChargeCapacity([in] uint32 arg2, [out] uint32 argr); 59 [WmiMethodId(3), Implemented, read, write, Description("Return Battery Manufacture Name.")] void BatteryManufactureName([in] uint32 arg2, [out] string argr); 60 [WmiMethodId(4), Implemented, read, write, Description("Return Battery Manufacture Date.")] void BatteryManufactureDate([in] uint32 arg2, [out] uint32 argr); 61 [WmiMethodId(5), Implemented, read, write, Description("Return Battery Serial Number.")] void BatterySerialNumber([in] uint32 arg2, [out] uint32 argr); 62 [WmiMethodId(6), Implemented, read, write, Description("Return Battery Chemistry Value.")] void BatteryChemistryValue([in] uint32 arg2, [out] string argr); 63 [WmiMethodId(7), Implemented, read, write, Description("Return Battery Temperature.")] void BatteryTemperature([in] uint32 arg2, [out] uint32 argr); 64 [WmiMethodId(8), Implemented, read, write, Description("Return Battery Current.")] void BatteryCurrent([in] uint32 arg2, [out] uint32 argr); 65 [WmiMethodId(9), Implemented, read, write, Description("Return Battery Voltage.")] void BatteryVoltage([in] uint32 arg2, [out] uint32 argr); 66 [WmiMethodId(10), Implemented, read, write, Description("Return Battery Manufacture Access(MA code).")] void BatteryManufactureAceess([in] uint32 arg2, [out] uint32 argr); 67 [WmiMethodId(11), Implemented, read, write, Description("Return Battery Relative State-Of-Charge.")] void BatteryRelativeStateOfCharge([in] uint32 arg2, [out] uint32 argr); 68 [WmiMethodId(12), Implemented, read, write, Description("Return Battery Cycle Count")] void BatteryCycleCount([in] uint32 arg2, [out] uint32 argr); 69 [WmiMethodId(13), Implemented, read, write, Description("Return Battery ePPID")] void BatteryePPID([in] uint32 arg2, [out] string argr); 70 [WmiMethodId(14), Implemented, read, write, Description("Return Battery Raw Analytics Start")] void BatteryeRawAnalyticsStart([in] uint32 arg2, [out] uint32 argr); 71 [WmiMethodId(15), Implemented, read, write, Description("Return Battery Raw Analytics")] void BatteryeRawAnalytics([in] uint32 arg2, [out] uint32 RawSize, [out, WmiSizeIs("RawSize") : ToInstance] uint8 RawData[]); 72 [WmiMethodId(16), Implemented, read, write, Description("Return Battery Design Voltage.")] void BatteryDesignVoltage([in] uint32 arg2, [out] uint32 argr); 73 [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[]); 74 [WmiMethodId(18), Implemented, read, write, Description("Return Version.")] void ReturnVersion([in] uint32 arg2, [out] uint32 argr); 75 [WmiMethodId(32), Implemented, read, write, Description("Return Fan Sensor Information")] void FanSensorInformation([in] uint32 arg2, [out] uint32 RawSize, [out, WmiSizeIs("RawSize") : ToInstance] uint8 RawData[]); 76 [WmiMethodId(34), Implemented, read, write, Description("Return Thermal Sensor Information")] void ThermalSensorInformation([in] uint32 arg2, [out] uint32 RawSize, [out, WmiSizeIs("RawSize") : ToInstance] uint8 RawData[]); 77 }; 78 79Each WMI method takes an ACPI buffer containing a 32-bit index as input argument, 80with the first 8 bit being used to specify the battery when using battery-related 81WMI methods. Other WMI methods may ignore this argument or interpret it 82differently. The WMI method output format varies: 83 84* if the function has only a single output, then an ACPI object 85 of the corresponding type is returned 86* if the function has multiple outputs, when an ACPI package 87 containing the outputs in the same order is returned 88 89The format of the output should be thoroughly checked, since many methods can 90return malformed data in case of an error. 91 92The data format of many battery-related methods seems to be based on the 93`Smart Battery Data Specification`, so unknown battery-related methods are 94likely to follow this standard in some way. 95 96WMI method GetBatteryDesignCapacity() 97------------------------------------- 98 99Returns the design capacity of the battery in mAh as an u16. 100 101WMI method BatteryFullCharge() 102------------------------------ 103 104Returns the full charge capacity of the battery in mAh as an u16. 105 106WMI method BatteryManufactureName() 107----------------------------------- 108 109Returns the manufacture name of the battery as an ASCII string. 110 111WMI method BatteryManufactureDate() 112----------------------------------- 113 114Returns the manufacture date of the battery as an u16. 115The date is encoded in the following manner: 116 117- bits 0 to 4 contain the manufacture day. 118- bits 5 to 8 contain the manufacture month. 119- bits 9 to 15 contain the manufacture year biased by 1980. 120 121.. note:: 122 The data format needs to be verified on more machines. 123 124WMI method BatterySerialNumber() 125-------------------------------- 126 127Returns the serial number of the battery as an u16. 128 129WMI method BatteryChemistryValue() 130---------------------------------- 131 132Returns the chemistry of the battery as an ASCII string. 133Known values are: 134 135- "Li-I" for Li-Ion 136 137WMI method BatteryTemperature() 138------------------------------- 139 140Returns the temperature of the battery in tenth degree kelvin as an u16. 141 142WMI method BatteryCurrent() 143--------------------------- 144 145Returns the current flow of the battery in mA as an s16. 146Negative values indicate discharging. 147 148WMI method BatteryVoltage() 149--------------------------- 150 151Returns the voltage flow of the battery in mV as an u16. 152 153WMI method BatteryManufactureAccess() 154------------------------------------- 155 156Returns a manufacture-defined value as an u16. 157 158WMI method BatteryRelativeStateOfCharge() 159----------------------------------------- 160 161Returns the capacity of the battery in percent as an u16. 162 163WMI method BatteryCycleCount() 164------------------------------ 165 166Returns the cycle count of the battery as an u16. 167 168WMI method BatteryePPID() 169------------------------- 170 171Returns the ePPID of the battery as an ASCII string. 172 173WMI method BatteryeRawAnalyticsStart() 174-------------------------------------- 175 176Performs an analysis of the battery and returns a status code: 177 178- ``0x0``: Success 179- ``0x1``: Interface not supported 180- ``0xfffffffe``: Error/Timeout 181 182.. note:: 183 The meaning of this method is still largely unknown. 184 185WMI method BatteryeRawAnalytics() 186--------------------------------- 187 188Returns a buffer usually containing 12 blocks of analytics data. 189Those blocks contain: 190 191- a block number starting with 0 (u8) 192- 31 bytes of unknown data 193 194.. note:: 195 The meaning of this method is still largely unknown. 196 197WMI method BatteryDesignVoltage() 198--------------------------------- 199 200Returns the design voltage of the battery in mV as an u16. 201 202WMI method BatteryeRawAnalyticsABlock() 203--------------------------------------- 204 205Returns a single block of analytics data, with the second byte 206of the index being used for selecting the block number. 207 208*Supported since WMI interface version 3!* 209 210.. note:: 211 The meaning of this method is still largely unknown. 212 213WMI method ReturnVersion() 214-------------------------- 215 216Returns the WMI interface version as an u32. 217 218WMI method FanSensorInformation() 219--------------------------------- 220 221Returns a buffer containing fan sensor entries, terminated 222with a single ``0xff``. 223Those entries contain: 224 225- fan type (u8) 226- fan speed in RPM (little endian u16) 227 228WMI method ThermalSensorInformation() 229------------------------------------- 230 231Returns a buffer containing thermal sensor entries, terminated 232with a single ``0xff``. 233Those entries contain: 234 235- thermal type (u8) 236- current temperature (s8) 237- min. temperature (s8) 238- max. temperature (s8) 239- unknown field (u8) 240 241.. note:: 242 TODO: Find out what the meaning of the last byte is. 243 244ACPI battery matching algorithm 245=============================== 246 247The algorithm used to match ACPI batteries to indices is based on information 248which was found inside the logging messages of the OEM software. 249 250Basically for each new ACPI battery, the serial numbers of the batteries behind 251indices 1 till 3 are compared with the serial number of the ACPI battery. 252Since the serial number of the ACPI battery can either be encoded as a normal 253integer or as a hexadecimal value, both cases need to be checked. The first 254index with a matching serial number is then selected. 255 256A serial number of 0 indicates that the corresponding index is not associated 257with an actual battery, or that the associated battery is not present. 258 259Some machines like the Dell Inspiron 3505 only support a single battery and thus 260ignore the battery index. Because of this the driver depends on the ACPI battery 261hook mechanism to discover batteries. 262 263.. note:: 264 The ACPI battery matching algorithm currently used inside the driver is 265 outdated and does not match the algorithm described above. The reasons for 266 this are differences in the handling of the ToHexString() ACPI opcode between 267 Linux and Windows, which distorts the serial number of ACPI batteries on many 268 machines. Until this issue is resolved, the driver cannot use the above 269 algorithm. 270 271Reverse-Engineering the DDV WMI interface 272========================================= 273 2741. Find a supported Dell notebook, usually made after ~2020. 2752. Dump the ACPI tables and search for the WMI device (usually called "ADDV"). 2763. Decode the corresponding bmof data and look at the ASL code. 2774. Try to deduce the meaning of a certain WMI method by comparing the control 278 flow with other ACPI methods (_BIX or _BIF for battery related methods 279 for example). 2805. Use the built-in UEFI diagostics to view sensor types/values for fan/thermal 281 related methods (sometimes overwriting static ACPI data fields can be used 282 to test different sensor type values, since on some machines this data is 283 not reinitialized upon a warm reset). 284 285Alternatively: 286 2871. Load the ``dell-wmi-ddv`` driver, use the ``force`` module param 288 if necessary. 2892. Use the debugfs interface to access the raw fan/thermal sensor buffer data. 2903. Compare the data with the built-in UEFI diagnostics. 291 292In case the DDV WMI interface version available on your Dell notebook is not 293supported or you are seeing unknown fan/thermal sensors, please submit a 294bugreport on `bugzilla <https://bugzilla.kernel.org>`_ so they can be added 295to the ``dell-wmi-ddv`` driver. 296 297See Documentation/admin-guide/reporting-issues.rst for further information. 298