Documentation/arm64/acpi_object_usage.txt

   1 ACPI Tables
   2 -----------
   3 The expectations of individual ACPI tables are discussed in the list that
   4 follows.
   5
   6 If a section number is used, it refers to a section number in the ACPI
   7 specification where the object is defined.  If "Signature Reserved" is used,
   8 the table signature (the first four bytes of the table) is the only portion
   9 of the table recognized by the specification, and the actual table is defined
  10 outside of the UEFI Forum (see Section 5.2.6 of the specification).
  11
  12 For ACPI on arm64, tables also fall into the following categories:
  13
  14        -- Required: DSDT, FADT, GTDT, MADT, MCFG, RSDP, SPCR, XSDT
  15
  16        -- Recommended: BERT, EINJ, ERST, HEST, PCCT, SSDT
  17
  18        -- Optional: BGRT, CPEP, CSRT, DBG2, DRTM, ECDT, FACS, FPDT, IORT,
  19           MCHI, MPST, MSCT, NFIT, PMTT, RASF, SBST, SLIT, SPMI, SRAT, STAO,
  20           TCPA, TPM2, UEFI, XENV
  21
  22        -- Not supported: BOOT, DBGP, DMAR, ETDT, HPET, IBFT, IVRS, LPIT,
  23           MSDM, OEMx, PSDT, RSDT, SLIC, WAET, WDAT, WDRT, WPBT
  24
  25 Table  Usage for ARMv8 Linux
  26 -----  ----------------------------------------------------------------
  27 BERT   Section 18.3 (signature == "BERT")
  28        == Boot Error Record Table ==
  29        Must be supplied if RAS support is provided by the platform.  It
  30        is recommended this table be supplied.
  31
  32 BOOT   Signature Reserved (signature == "BOOT")
  33        == simple BOOT flag table ==
  34        Microsoft only table, will not be supported.
  35
  36 BGRT   Section 5.2.22 (signature == "BGRT")
  37        == Boot Graphics Resource Table ==
  38        Optional, not currently supported, with no real use-case for an
  39        ARM server.
  40
  41 CPEP   Section 5.2.18 (signature == "CPEP")
  42        == Corrected Platform Error Polling table ==
  43        Optional, not currently supported, and not recommended until such
  44        time as ARM-compatible hardware is available, and the specification
  45        suitably modified.
  46
  47 CSRT   Signature Reserved (signature == "CSRT")
  48        == Core System Resources Table ==
  49        Optional, not currently supported.
  50
  51 DBG2   Signature Reserved (signature == "DBG2")
  52        == DeBuG port table 2 ==
  53        License has changed and should be usable.  Optional if used instead
  54        of earlycon=<device> on the command line.
  55
  56 DBGP   Signature Reserved (signature == "DBGP")
  57        == DeBuG Port table ==
  58        Microsoft only table, will not be supported.
  59
  60 DSDT   Section 5.2.11.1 (signature == "DSDT")
  61        == Differentiated System Description Table ==
  62        A DSDT is required; see also SSDT.
  63
  64        ACPI tables contain only one DSDT but can contain one or more SSDTs,
  65        which are optional.  Each SSDT can only add to the ACPI namespace,
  66        but cannot modify or replace anything in the DSDT.
  67
  68 DMAR   Signature Reserved (signature == "DMAR")
  69        == DMA Remapping table ==
  70        x86 only table, will not be supported.
  71
  72 DRTM   Signature Reserved (signature == "DRTM")
  73        == Dynamic Root of Trust for Measurement table ==
  74        Optional, not currently supported.
  75
  76 ECDT   Section 5.2.16 (signature == "ECDT")
  77        == Embedded Controller Description Table ==
  78        Optional, not currently supported, but could be used on ARM if and
  79        only if one uses the GPE_BIT field to represent an IRQ number, since
  80        there are no GPE blocks defined in hardware reduced mode.  This would
  81        need to be modified in the ACPI specification.
  82
  83 EINJ   Section 18.6 (signature == "EINJ")
  84        == Error Injection table ==
  85        This table is very useful for testing platform response to error
  86        conditions; it allows one to inject an error into the system as
  87        if it had actually occurred.  However, this table should not be
  88        shipped with a production system; it should be dynamically loaded
  89        and executed with the ACPICA tools only during testing.
  90
  91 ERST   Section 18.5 (signature == "ERST")
  92        == Error Record Serialization Table ==
  93        On a platform supports RAS, this table must be supplied if it is not
  94        UEFI-based; if it is UEFI-based, this table may be supplied. When this
  95        table is not present, UEFI run time service will be utilized to save
  96        and retrieve hardware error information to and from a persistent store.
  97
  98 ETDT   Signature Reserved (signature == "ETDT")
  99        == Event Timer Description Table ==
 100        Obsolete table, will not be supported.
 101
 102 FACS   Section 5.2.10 (signature == "FACS")
 103        == Firmware ACPI Control Structure ==
 104        It is unlikely that this table will be terribly useful.  If it is
 105        provided, the Global Lock will NOT be used since it is not part of
 106        the hardware reduced profile, and only 64-bit address fields will
 107        be considered valid.
 108
 109 FADT   Section 5.2.9 (signature == "FACP")
 110        == Fixed ACPI Description Table ==
 111        Required for arm64.
 112
 113        The HW_REDUCED_ACPI flag must be set.  All of the fields that are
 114        to be ignored when HW_REDUCED_ACPI is set are expected to be set to
 115        zero.
 116
 117        If an FACS table is provided, the X_FIRMWARE_CTRL field is to be
 118        used, not FIRMWARE_CTRL.
 119
 120        If PSCI is used (as is recommended), make sure that ARM_BOOT_ARCH is
 121        filled in properly -- that the PSCI_COMPLIANT flag is set and that
 122        PSCI_USE_HVC is set or unset as needed (see table 5-37).
 123
 124        For the DSDT that is also required, the X_DSDT field is to be used,
 125        not the DSDT field.
 126
 127 FPDT   Section 5.2.23 (signature == "FPDT")
 128        == Firmware Performance Data Table ==
 129        Optional, not currently supported.
 130
 131 GTDT   Section 5.2.24 (signature == "GTDT")
 132        == Generic Timer Description Table ==
 133        Required for arm64.
 134
 135 HEST   Section 18.3.2 (signature == "HEST")
 136        == Hardware Error Source Table ==
 137        ARM-specific error sources have been defined; please use those or the
 138        PCI types such as type 6 (AER Root Port), 7 (AER Endpoint), or 8 (AER
 139        Bridge), or use type 9 (Generic Hardware Error Source).  Firmware first
 140        error handling is possible if and only if Trusted Firmware is being
 141        used on arm64.
 142
 143        Must be supplied if RAS support is provided by the platform.  It
 144        is recommended this table be supplied.
 145
 146 HPET   Signature Reserved (signature == "HPET")
 147        == High Precision Event timer Table ==
 148        x86 only table, will not be supported.
 149
 150 IBFT   Signature Reserved (signature == "IBFT")
 151        == iSCSI Boot Firmware Table ==
 152        Microsoft defined table, support TBD.
 153
 154 IORT   Signature Reserved (signature == "IORT")
 155        == Input Output Remapping Table ==
 156        arm64 only table, required in order to describe IO topology, SMMUs,
 157        and GIC ITSs, and how those various components are connected together,
 158        such as identifying which components are behind which SMMUs/ITSs.
 159        This table will only be required on certain SBSA platforms (e.g.,
 160        when using GICv3-ITS and an SMMU); on SBSA Level 0 platforms, it
 161        remains optional.
 162
 163 IVRS   Signature Reserved (signature == "IVRS")
 164        == I/O Virtualization Reporting Structure ==
 165        x86_64 (AMD) only table, will not be supported.
 166
 167 LPIT   Signature Reserved (signature == "LPIT")
 168        == Low Power Idle Table ==
 169        x86 only table as of ACPI 5.1; starting with ACPI 6.0, processor
 170        descriptions and power states on ARM platforms should use the DSDT
 171        and define processor container devices (_HID ACPI0010, Section 8.4,
 172        and more specifically 8.4.3 and and 8.4.4).
 173
 174 MADT   Section 5.2.12 (signature == "APIC")
 175        == Multiple APIC Description Table ==
 176        Required for arm64.  Only the GIC interrupt controller structures
 177        should be used (types 0xA - 0xF).
 178
 179 MCFG   Signature Reserved (signature == "MCFG")
 180        == Memory-mapped ConFiGuration space ==
 181        If the platform supports PCI/PCIe, an MCFG table is required.
 182
 183 MCHI   Signature Reserved (signature == "MCHI")
 184        == Management Controller Host Interface table ==
 185        Optional, not currently supported.
 186
 187 MPST   Section 5.2.21 (signature == "MPST")
 188        == Memory Power State Table ==
 189        Optional, not currently supported.
 190
 191 MSCT   Section 5.2.19 (signature == "MSCT")
 192        == Maximum System Characteristic Table ==
 193        Optional, not currently supported.
 194
 195 MSDM   Signature Reserved (signature == "MSDM")
 196        == Microsoft Data Management table ==
 197        Microsoft only table, will not be supported.
 198
 199 NFIT   Section 5.2.25 (signature == "NFIT")
 200        == NVDIMM Firmware Interface Table ==
 201        Optional, not currently supported.
 202
 203 OEMx   Signature of "OEMx" only
 204        == OEM Specific Tables ==
 205        All tables starting with a signature of "OEM" are reserved for OEM
 206        use.  Since these are not meant to be of general use but are limited
 207        to very specific end users, they are not recommended for use and are
 208        not supported by the kernel for arm64.
 209
 210 PCCT   Section 14.1 (signature == "PCCT)
 211        == Platform Communications Channel Table ==
 212        Recommend for use on arm64; use of PCC is recommended when using CPPC
 213        to control performance and power for platform processors.
 214
 215 PMTT   Section 5.2.21.12 (signature == "PMTT")
 216        == Platform Memory Topology Table ==
 217        Optional, not currently supported.
 218
 219 PSDT   Section 5.2.11.3 (signature == "PSDT")
 220        == Persistent System Description Table ==
 221        Obsolete table, will not be supported.
 222
 223 RASF   Section 5.2.20 (signature == "RASF")
 224        == RAS Feature table ==
 225        Optional, not currently supported.
 226
 227 RSDP   Section 5.2.5 (signature == "RSD PTR")
 228        == Root System Description PoinTeR ==
 229        Required for arm64.
 230
 231 RSDT   Section 5.2.7 (signature == "RSDT")
 232        == Root System Description Table ==
 233        Since this table can only provide 32-bit addresses, it is deprecated
 234        on arm64, and will not be used.  If provided, it will be ignored.
 235
 236 SBST   Section 5.2.14 (signature == "SBST")
 237        == Smart Battery Subsystem Table ==
 238        Optional, not currently supported.
 239
 240 SLIC   Signature Reserved (signature == "SLIC")
 241        == Software LIcensing table ==
 242        Microsoft only table, will not be supported.
 243
 244 SLIT   Section 5.2.17 (signature == "SLIT")
 245        == System Locality distance Information Table ==
 246        Optional in general, but required for NUMA systems.
 247
 248 SPCR   Signature Reserved (signature == "SPCR")
 249        == Serial Port Console Redirection table ==
 250        Required for arm64.
 251
 252 SPMI   Signature Reserved (signature == "SPMI")
 253        == Server Platform Management Interface table ==
 254        Optional, not currently supported.
 255
 256 SRAT   Section 5.2.16 (signature == "SRAT")
 257        == System Resource Affinity Table ==
 258        Optional, but if used, only the GICC Affinity structures are read.
 259        To support arm64 NUMA, this table is required.
 260
 261 SSDT   Section 5.2.11.2 (signature == "SSDT")
 262        == Secondary System Description Table ==
 263        These tables are a continuation of the DSDT; these are recommended
 264        for use with devices that can be added to a running system, but can
 265        also serve the purpose of dividing up device descriptions into more
 266        manageable pieces.
 267
 268        An SSDT can only ADD to the ACPI namespace.  It cannot modify or
 269        replace existing device descriptions already in the namespace.
 270
 271        These tables are optional, however.  ACPI tables should contain only
 272        one DSDT but can contain many SSDTs.
 273
 274 STAO   Signature Reserved (signature == "STAO")
 275        == _STA Override table ==
 276        Optional, but only necessary in virtualized environments in order to
 277        hide devices from guest OSs.
 278
 279 TCPA   Signature Reserved (signature == "TCPA")
 280        == Trusted Computing Platform Alliance table ==
 281        Optional, not currently supported, and may need changes to fully
 282        interoperate with arm64.
 283
 284 TPM2   Signature Reserved (signature == "TPM2")
 285        == Trusted Platform Module 2 table ==
 286        Optional, not currently supported, and may need changes to fully
 287        interoperate with arm64.
 288
 289 UEFI   Signature Reserved (signature == "UEFI")
 290        == UEFI ACPI data table ==
 291        Optional, not currently supported.  No known use case for arm64,
 292        at present.
 293
 294 WAET   Signature Reserved (signature == "WAET")
 295        == Windows ACPI Emulated devices Table ==
 296        Microsoft only table, will not be supported.
 297
 298 WDAT   Signature Reserved (signature == "WDAT")
 299        == Watch Dog Action Table ==
 300        Microsoft only table, will not be supported.
 301
 302 WDRT   Signature Reserved (signature == "WDRT")
 303        == Watch Dog Resource Table ==
 304        Microsoft only table, will not be supported.
 305
 306 WPBT   Signature Reserved (signature == "WPBT")
 307        == Windows Platform Binary Table ==
 308        Microsoft only table, will not be supported.
 309
 310 XENV   Signature Reserved (signature == "XENV")
 311        == Xen project table ==
 312        Optional, used only by Xen at present.
 313
 314 XSDT   Section 5.2.8 (signature == "XSDT")
 315        == eXtended System Description Table ==
 316        Required for arm64.
 317
 318
 319 ACPI Objects
 320 ------------
 321 The expectations on individual ACPI objects that are likely to be used are
 322 shown in the list that follows; any object not explicitly mentioned below
 323 should be used as needed for a particular platform or particular subsystem,
 324 such as power management or PCI.
 325
 326 Name   Section         Usage for ARMv8 Linux
 327 ----   ------------    -------------------------------------------------
 328 _CCA   6.2.17          This method must be defined for all bus masters
 329                        on arm64 -- there are no assumptions made about
 330                        whether such devices are cache coherent or not.
 331                        The _CCA value is inherited by all descendants of
 332                        these devices so it does not need to be repeated.
 333                        Without _CCA on arm64, the kernel does not know what
 334                        to do about setting up DMA for the device.
 335
 336                        NB: this method provides default cache coherency
 337                        attributes; the presence of an SMMU can be used to
 338                        modify that, however.  For example, a master could
 339                        default to non-coherent, but be made coherent with
 340                        the appropriate SMMU configuration (see Table 17 of
 341                        the IORT specification, ARM Document DEN 0049B).
 342
 343 _CID   6.1.2           Use as needed, see also _HID.
 344
 345 _CLS   6.1.3           Use as needed, see also _HID.
 346
 347 _CPC   8.4.7.1         Use as needed, power management specific.  CPPC is
 348                        recommended on arm64.
 349
 350 _CRS   6.2.2           Required on arm64.
 351
 352 _CSD   8.4.2.2         Use as needed, used only in conjunction with _CST.
 353
 354 _CST   8.4.2.1         Low power idle states (8.4.4) are recommended instead
 355                        of C-states.
 356
 357 _DDN   6.1.4           This field can be used for a device name.  However,
 358                        it is meant for DOS device names (e.g., COM1), so be
 359                        careful of its use across OSes.
 360
 361 _DSD   6.2.5           To be used with caution.  If this object is used, try
 362                        to use it within the constraints already defined by the
 363                        Device Properties UUID.  Only in rare circumstances
 364                        should it be necessary to create a new _DSD UUID.
 365
 366                        In either case, submit the _DSD definition along with
 367                        any driver patches for discussion, especially when
 368                        device properties are used.  A driver will not be
 369                        considered complete without a corresponding _DSD
 370                        description.  Once approved by kernel maintainers,
 371                        the UUID or device properties must then be registered
 372                        with the UEFI Forum; this may cause some iteration as
 373                        more than one OS will be registering entries.
 374
 375 _DSM   9.1.1           Do not use this method.  It is not standardized, the
 376                        return values are not well documented, and it is
 377                        currently a frequent source of error.
 378
 379 \_GL   5.7.1           This object is not to be used in hardware reduced
 380                        mode, and therefore should not be used on arm64.
 381
 382 _GLK   6.5.7           This object requires a global lock be defined; there
 383                        is no global lock on arm64 since it runs in hardware
 384                        reduced mode.  Hence, do not use this object on arm64.
 385
 386 \_GPE  5.3.1           This namespace is for x86 use only.  Do not use it
 387                        on arm64.
 388
 389 _HID   6.1.5           This is the primary object to use in device probing,
 390                        though _CID and _CLS may also be used.
 391
 392 _INI   6.5.1           Not required, but can be useful in setting up devices
 393                        when UEFI leaves them in a state that may not be what
 394                        the driver expects before it starts probing.
 395
 396 _LPI   8.4.4.3         Recommended for use with processor definitions (_HID
 397                        ACPI0010) on arm64.  See also _RDI.
 398
 399 _MLS   6.1.7           Highly recommended for use in internationalization.
 400
 401 _OFF   7.2.2           It is recommended to define this method for any device
 402                        that can be turned on or off.
 403
 404 _ON    7.2.3           It is recommended to define this method for any device
 405                        that can be turned on or off.
 406
 407 \_OS   5.7.3           This method will return "Linux" by default (this is
 408                        the value of the macro ACPI_OS_NAME on Linux).  The
 409                        command line parameter acpi_os=<string> can be used
 410                        to set it to some other value.
 411
 412 _OSC   6.2.11          This method can be a global method in ACPI (i.e.,
 413                        \_SB._OSC), or it may be associated with a specific
 414                        device (e.g., \_SB.DEV0._OSC), or both.  When used
 415                        as a global method, only capabilities published in
 416                        the ACPI specification are allowed.  When used as
 417                        a device-specific method, the process described for
 418                        using _DSD MUST be used to create an _OSC definition;
 419                        out-of-process use of _OSC is not allowed.  That is,
 420                        submit the device-specific _OSC usage description as
 421                        part of the kernel driver submission, get it approved
 422                        by the kernel community, then register it with the
 423                        UEFI Forum.
 424
 425 \_OSI  5.7.2           Deprecated on ARM64.  As far as ACPI firmware is
 426                        concerned, _OSI is not to be used to determine what
 427                        sort of system is being used or what functionality
 428                        is provided.  The _OSC method is to be used instead.
 429
 430 _PDC   8.4.1           Deprecated, do not use on arm64.
 431
 432 \_PIC  5.8.1           The method should not be used.  On arm64, the only
 433                        interrupt model available is GIC.
 434
 435 \_PR   5.3.1           This namespace is for x86 use only on legacy systems.
 436                        Do not use it on arm64.
 437
 438 _PRT   6.2.13          Required as part of the definition of all PCI root
 439                        devices.
 440
 441 _PRx   7.3.8-11        Use as needed; power management specific.  If _PR0 is
 442                        defined, _PR3 must also be defined.
 443
 444 _PSx   7.3.2-5         Use as needed; power management specific.  If _PS0 is
 445                        defined, _PS3 must also be defined.  If clocks or
 446                        regulators need adjusting to be consistent with power
 447                        usage, change them in these methods.
 448
 449 _RDI   8.4.4.4         Recommended for use with processor definitions (_HID
 450                        ACPI0010) on arm64.  This should only be used in
 451                        conjunction with _LPI.
 452
 453 \_REV  5.7.4           Always returns the latest version of ACPI supported.
 454
 455 \_SB   5.3.1           Required on arm64; all devices must be defined in this
 456                        namespace.
 457
 458 _SLI   6.2.15          Use is recommended when SLIT table is in use.
 459
 460 _STA   6.3.7,          It is recommended to define this method for any device
 461        7.2.4           that can be turned on or off.  See also the STAO table
 462                        that provides overrides to hide devices in virtualized
 463                        environments.
 464
 465 _SRS   6.2.16          Use as needed; see also _PRS.
 466
 467 _STR   6.1.10          Recommended for conveying device names to end users;
 468                        this is preferred over using _DDN.
 469
 470 _SUB   6.1.9           Use as needed; _HID or _CID are preferred.
 471
 472 _SUN   6.1.11          Use as needed, but recommended.
 473
 474 _SWS   7.4.3           Use as needed; power management specific; this may
 475                        require specification changes for use on arm64.
 476
 477 _UID   6.1.12          Recommended for distinguishing devices of the same
 478                        class; define it if at all possible.
 479
 480
 481
 482
 483 ACPI Event Model
 484 ----------------
 485 Do not use GPE block devices; these are not supported in the hardware reduced
 486 profile used by arm64.  Since there are no GPE blocks defined for use on ARM
 487 platforms, ACPI events must be signaled differently.
 488
 489 There are two options: GPIO-signaled interrupts (Section 5.6.5), and
 490 interrupt-signaled events (Section 5.6.9).  Interrupt-signaled events are a
 491 new feature in the ACPI 6.1 specification.  Either -- or both -- can be used
 492 on a given platform, and which to use may be dependent of limitations in any
 493 given SoC.  If possible, interrupt-signaled events are recommended.
 494
 495
 496 ACPI Processor Control
 497 ----------------------
 498 Section 8 of the ACPI specification changed significantly in version 6.0.
 499 Processors should now be defined as Device objects with _HID ACPI0007; do
 500 not use the deprecated Processor statement in ASL.  All multiprocessor systems
 501 should also define a hierarchy of processors, done with Processor Container
 502 Devices (see Section 8.4.3.1, _HID ACPI0010); do not use processor aggregator
 503 devices (Section 8.5) to describe processor topology.  Section 8.4 of the
 504 specification describes the semantics of these object definitions and how
 505 they interrelate.
 506
 507 Most importantly, the processor hierarchy defined also defines the low power
 508 idle states that are available to the platform, along with the rules for
 509 determining which processors can be turned on or off and the circumstances
 510 that control that.  Without this information, the processors will run in
 511 whatever power state they were left in by UEFI.
 512
 513 Note too, that the processor Device objects defined and the entries in the
 514 MADT for GICs are expected to be in synchronization.  The _UID of the Device
 515 object must correspond to processor IDs used in the MADT.
 516
 517 It is recommended that CPPC (8.4.5) be used as the primary model for processor
 518 performance control on arm64.  C-states and P-states may become available at
 519 some point in the future, but most current design work appears to favor CPPC.
 520
 521 Further, it is essential that the ARMv8 SoC provide a fully functional
 522 implementation of PSCI; this will be the only mechanism supported by ACPI
 523 to control CPU power state.  Booting of secondary CPUs using the ACPI
 524 parking protocol is possible, but discouraged, since only PSCI is supported
 525 for ARM servers.
 526
 527
 528 ACPI System Address Map Interfaces
 529 ----------------------------------
 530 In Section 15 of the ACPI specification, several methods are mentioned as
 531 possible mechanisms for conveying memory resource information to the kernel.
 532 For arm64, we will only support UEFI for booting with ACPI, hence the UEFI
 533 GetMemoryMap() boot service is the only mechanism that will be used.
 534
 535
 536 ACPI Platform Error Interfaces (APEI)
 537 -------------------------------------
 538 The APEI tables supported are described above.
 539
 540 APEI requires the equivalent of an SCI and an NMI on ARMv8.  The SCI is used
 541 to notify the OSPM of errors that have occurred but can be corrected and the
 542 system can continue correct operation, even if possibly degraded.  The NMI is
 543 used to indicate fatal errors that cannot be corrected, and require immediate
 544 attention.
 545
 546 Since there is no direct equivalent of the x86 SCI or NMI, arm64 handles
 547 these slightly differently.  The SCI is handled as a high priority interrupt;
 548 given that these are corrected (or correctable) errors being reported, this
 549 is sufficient.  The NMI is emulated as the highest priority interrupt
 550 possible.  This implies some caution must be used since there could be
 551 interrupts at higher privilege levels or even interrupts at the same priority
 552 as the emulated NMI.  In Linux, this should not be the case but one should
 553 be aware it could happen.
 554
 555
 556 ACPI Objects Not Supported on ARM64
 557 -----------------------------------
 558 While this may change in the future, there are several classes of objects
 559 that can be defined, but are not currently of general interest to ARM servers.
 560 Some of these objects have x86 equivalents, and may actually make sense in ARM
 561 servers.  However, there is either no hardware available at present, or there
 562 may not even be a non-ARM implementation yet.  Hence, they are not currently
 563 supported.
 564
 565 The following classes of objects are not supported:
 566
 567        -- Section 9.2: ambient light sensor devices
 568
 569        -- Section 9.3: battery devices
 570
 571        -- Section 9.4: lids (e.g., laptop lids)
 572
 573        -- Section 9.8.2: IDE controllers
 574
 575        -- Section 9.9: floppy controllers
 576
 577        -- Section 9.10: GPE block devices
 578
 579        -- Section 9.15: PC/AT RTC/CMOS devices
 580
 581        -- Section 9.16: user presence detection devices
 582
 583        -- Section 9.17: I/O APIC devices; all GICs must be enumerable via MADT
 584
 585        -- Section 9.18: time and alarm devices (see 9.15)
 586
 587        -- Section 10: power source and power meter devices
 588
 589        -- Section 11: thermal management
 590
 591        -- Section 12: embedded controllers interface
 592
 593        -- Section 13: SMBus interfaces
 594
 595
 596 This also means that there is no support for the following objects:
 597
 598 Name   Section                     Name   Section
 599 ----   ------------                ----   ------------
 600 _ALC   9.3.4                       _FDM   9.10.3
 601 _ALI   9.3.2                       _FIX   6.2.7
 602 _ALP   9.3.6                       _GAI   10.4.5
 603 _ALR   9.3.5                       _GHL   10.4.7
 604 _ALT   9.3.3                       _GTM   9.9.2.1.1
 605 _BCT   10.2.2.10                   _LID   9.5.1
 606 _BDN   6.5.3                       _PAI   10.4.4
 607 _BIF   10.2.2.1                    _PCL   10.3.2
 608 _BIX   10.2.2.1                    _PIF   10.3.3
 609 _BLT   9.2.3                       _PMC   10.4.1
 610 _BMA   10.2.2.4                    _PMD   10.4.8
 611 _BMC   10.2.2.12                   _PMM   10.4.3
 612 _BMD   10.2.2.11                   _PRL   10.3.4
 613 _BMS   10.2.2.5                    _PSR   10.3.1
 614 _BST   10.2.2.6                    _PTP   10.4.2
 615 _BTH   10.2.2.7                    _SBS   10.1.3
 616 _BTM   10.2.2.9                    _SHL   10.4.6
 617 _BTP   10.2.2.8                    _STM   9.9.2.1.1
 618 _DCK   6.5.2                       _UPD   9.16.1
 619 _EC    12.12                       _UPP   9.16.2
 620 _FDE   9.10.1                      _WPC   10.5.2
 621 _FDI   9.10.2                      _WPP   10.5.3
 622