1 .. SPDX-License-Identifier: GPL-2.0-or-later 2 3 ================== 4 ACPI WMI interface 5 ================== 6 7 The ACPI WMI interface is a proprietary extension of the ACPI specification made 8 by Microsoft to allow hardware vendors to embed WMI (Windows Management Instrumentation) 9 objects inside their ACPI firmware. Typical functions implemented over ACPI WMI 10 are hotkey events on modern notebooks and configuration of BIOS options. 11 12 PNP0C14 ACPI device 13 ------------------- 14 15 Discovery of WMI objects is handled by defining ACPI devices with a PNP ID 16 of ``PNP0C14``. These devices will contain a set of ACPI buffers and methods 17 used for mapping and execution of WMI methods and/or queries. If there exist 18 multiple of such devices, then each device is required to have a 19 unique ACPI UID. 20 21 _WDG buffer 22 ----------- 23 24 The ``_WDG`` buffer is used to discover WMI objects and is required to be 25 static. Its internal structure consists of data blocks with a size of 20 bytes, 26 containing the following data: 27 28 ======= =============== ===================================================== 29 Offset Size (in bytes) Content 30 ======= =============== ===================================================== 31 0x00 16 128 bit Variant 2 object GUID. 32 0x10 2 2 character method ID or single byte notification ID. 33 0x12 1 Object instance count. 34 0x13 1 Object flags. 35 ======= =============== ===================================================== 36 37 The WMI object flags control whether the method or notification ID is used: 38 39 - 0x1: Data block usage is expensive and must be explicitly enabled/disabled. 40 - 0x2: Data block contains WMI methods. 41 - 0x4: Data block contains ASCIZ string. 42 - 0x8: Data block describes a WMI event, use notification ID instead 43 of method ID. 44 45 Each WMI object GUID can appear multiple times inside a system. 46 The method/notification ID is used to construct the ACPI method names used for 47 interacting with the WMI object. 48 49 WQxx ACPI methods 50 ----------------- 51 52 If a data block does not contain WMI methods, then its content can be retrieved 53 by this required ACPI method. The last two characters of the ACPI method name 54 are the method ID of the data block to query. Their single parameter is an 55 integer describing the instance which should be queried. This parameter can be 56 omitted if the data block contains only a single instance. 57 58 WSxx ACPI methods 59 ----------------- 60 61 Similar to the ``WQxx`` ACPI methods, except that it is optional and takes an 62 additional buffer as its second argument. The instance argument also cannot 63 be omitted. 64 65 WMxx ACPI methods 66 ----------------- 67 68 Used for executing WMI methods associated with a data block. The last two 69 characters of the ACPI method name are the method ID of the data block 70 containing the WMI methods. Their first parameter is a integer describing the 71 instance which methods should be executed. The second parameter is an integer 72 describing the WMI method ID to execute, and the third parameter is a buffer 73 containing the WMI method parameters. If the data block is marked as containing 74 an ASCIZ string, then this buffer should contain an ASCIZ string. The ACPI 75 method will return the result of the executed WMI method. 76 77 WExx ACPI methods 78 ----------------- 79 80 Used for optionally enabling/disabling WMI events, the last two characters of 81 the ACPI method are the notification ID of the data block describing the WMI 82 event as hexadecimal value. Their first parameter is an integer with a value 83 of 0 if the WMI event should be disabled, other values will enable 84 the WMI event. 85 86 WCxx ACPI methods 87 ----------------- 88 Similar to the ``WExx`` ACPI methods, except that it controls data collection 89 instead of events and thus the last two characters of the ACPI method name are 90 the method ID of the data block to enable/disable. 91 92 _WED ACPI method 93 ---------------- 94 95 Used to retrieve additional WMI event data, its single parameter is a integer 96 holding the notification ID of the event. This method should be evaluated every 97 time an ACPI notification is received, since some ACPI implementations use a 98 queue to store WMI event data items. This queue will overflow after a couple 99 of WMI events are received without retrieving the associated WMI event data.
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.