reactos/drivers/bus/acpi/acpica/utilities/utresrc.c

   1 /*******************************************************************************
   2  *
   3  * Module Name: utresrc - Resource management utilities
   4  *
   5  ******************************************************************************/
   6
   7 /*
   8  * Copyright (C) 2000 - 2017, Intel Corp.
   9  * All rights reserved.
  10  *
  11  * Redistribution and use in source and binary forms, with or without
  12  * modification, are permitted provided that the following conditions
  13  * are met:
  14  * 1. Redistributions of source code must retain the above copyright
  15  *    notice, this list of conditions, and the following disclaimer,
  16  *    without modification.
  17  * 2. Redistributions in binary form must reproduce at minimum a disclaimer
  18  *    substantially similar to the "NO WARRANTY" disclaimer below
  19  *    ("Disclaimer") and any redistribution must be conditioned upon
  20  *    including a substantially similar Disclaimer requirement for further
  21  *    binary redistribution.
  22  * 3. Neither the names of the above-listed copyright holders nor the names
  23  *    of any contributors may be used to endorse or promote products derived
  24  *    from this software without specific prior written permission.
  25  *
  26  * Alternatively, this software may be distributed under the terms of the
  27  * GNU General Public License ("GPL") version 2 as published by the Free
  28  * Software Foundation.
  29  *
  30  * NO WARRANTY
  31  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  32  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  33  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR
  34  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  35  * HOLDERS OR CONTRIBUTORS BE LIABLE FOR SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  36  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  37  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  38  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
  39  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
  40  * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  41  * POSSIBILITY OF SUCH DAMAGES.
  42  */
  43
  44 #include "acpi.h"
  45 #include "accommon.h"
  46 #include "acresrc.h"
  47
  48
  49 #define _COMPONENT          ACPI_UTILITIES
  50         ACPI_MODULE_NAME    ("utresrc")
  51
  52
  53 /*
  54  * Base sizes of the raw AML resource descriptors, indexed by resource type.
  55  * Zero indicates a reserved (and therefore invalid) resource type.
  56  */
  57 const UINT8                 AcpiGbl_ResourceAmlSizes[] =
  58 {
  59     /* Small descriptors */
  60
  61     0,
  62     0,
  63     0,
  64     0,
  65     ACPI_AML_SIZE_SMALL (AML_RESOURCE_IRQ),
  66     ACPI_AML_SIZE_SMALL (AML_RESOURCE_DMA),
  67     ACPI_AML_SIZE_SMALL (AML_RESOURCE_START_DEPENDENT),
  68     ACPI_AML_SIZE_SMALL (AML_RESOURCE_END_DEPENDENT),
  69     ACPI_AML_SIZE_SMALL (AML_RESOURCE_IO),
  70     ACPI_AML_SIZE_SMALL (AML_RESOURCE_FIXED_IO),
  71     ACPI_AML_SIZE_SMALL (AML_RESOURCE_FIXED_DMA),
  72     0,
  73     0,
  74     0,
  75     ACPI_AML_SIZE_SMALL (AML_RESOURCE_VENDOR_SMALL),
  76     ACPI_AML_SIZE_SMALL (AML_RESOURCE_END_TAG),
  77
  78     /* Large descriptors */
  79
  80     0,
  81     ACPI_AML_SIZE_LARGE (AML_RESOURCE_MEMORY24),
  82     ACPI_AML_SIZE_LARGE (AML_RESOURCE_GENERIC_REGISTER),
  83     0,
  84     ACPI_AML_SIZE_LARGE (AML_RESOURCE_VENDOR_LARGE),
  85     ACPI_AML_SIZE_LARGE (AML_RESOURCE_MEMORY32),
  86     ACPI_AML_SIZE_LARGE (AML_RESOURCE_FIXED_MEMORY32),
  87     ACPI_AML_SIZE_LARGE (AML_RESOURCE_ADDRESS32),
  88     ACPI_AML_SIZE_LARGE (AML_RESOURCE_ADDRESS16),
  89     ACPI_AML_SIZE_LARGE (AML_RESOURCE_EXTENDED_IRQ),
  90     ACPI_AML_SIZE_LARGE (AML_RESOURCE_ADDRESS64),
  91     ACPI_AML_SIZE_LARGE (AML_RESOURCE_EXTENDED_ADDRESS64),
  92     ACPI_AML_SIZE_LARGE (AML_RESOURCE_GPIO),
  93     ACPI_AML_SIZE_LARGE (AML_RESOURCE_PIN_FUNCTION),
  94     ACPI_AML_SIZE_LARGE (AML_RESOURCE_COMMON_SERIALBUS),
  95     ACPI_AML_SIZE_LARGE (AML_RESOURCE_PIN_CONFIG),
  96     ACPI_AML_SIZE_LARGE (AML_RESOURCE_PIN_GROUP),
  97     ACPI_AML_SIZE_LARGE (AML_RESOURCE_PIN_GROUP_FUNCTION),
  98     ACPI_AML_SIZE_LARGE (AML_RESOURCE_PIN_GROUP_CONFIG),
  99 };
 100
 101 const UINT8                 AcpiGbl_ResourceAmlSerialBusSizes[] =
 102 {
 103     0,
 104     ACPI_AML_SIZE_LARGE (AML_RESOURCE_I2C_SERIALBUS),
 105     ACPI_AML_SIZE_LARGE (AML_RESOURCE_SPI_SERIALBUS),
 106     ACPI_AML_SIZE_LARGE (AML_RESOURCE_UART_SERIALBUS),
 107 };
 108
 109
 110 /*
 111  * Resource types, used to validate the resource length field.
 112  * The length of fixed-length types must match exactly, variable
 113  * lengths must meet the minimum required length, etc.
 114  * Zero indicates a reserved (and therefore invalid) resource type.
 115  */
 116 static const UINT8          AcpiGbl_ResourceTypes[] =
 117 {
 118     /* Small descriptors */
 119
 120     0,
 121     0,
 122     0,
 123     0,
 124     ACPI_SMALL_VARIABLE_LENGTH,     /* 04 IRQ */
 125     ACPI_FIXED_LENGTH,              /* 05 DMA */
 126     ACPI_SMALL_VARIABLE_LENGTH,     /* 06 StartDependentFunctions */
 127     ACPI_FIXED_LENGTH,              /* 07 EndDependentFunctions */
 128     ACPI_FIXED_LENGTH,              /* 08 IO */
 129     ACPI_FIXED_LENGTH,              /* 09 FixedIO */
 130     ACPI_FIXED_LENGTH,              /* 0A FixedDMA */
 131     0,
 132     0,
 133     0,
 134     ACPI_VARIABLE_LENGTH,           /* 0E VendorShort */
 135     ACPI_FIXED_LENGTH,              /* 0F EndTag */
 136
 137     /* Large descriptors */
 138
 139     0,
 140     ACPI_FIXED_LENGTH,              /* 01 Memory24 */
 141     ACPI_FIXED_LENGTH,              /* 02 GenericRegister */
 142     0,
 143     ACPI_VARIABLE_LENGTH,           /* 04 VendorLong */
 144     ACPI_FIXED_LENGTH,              /* 05 Memory32 */
 145     ACPI_FIXED_LENGTH,              /* 06 Memory32Fixed */
 146     ACPI_VARIABLE_LENGTH,           /* 07 Dword* address */
 147     ACPI_VARIABLE_LENGTH,           /* 08 Word* address */
 148     ACPI_VARIABLE_LENGTH,           /* 09 ExtendedIRQ */
 149     ACPI_VARIABLE_LENGTH,           /* 0A Qword* address */
 150     ACPI_FIXED_LENGTH,              /* 0B Extended* address */
 151     ACPI_VARIABLE_LENGTH,           /* 0C Gpio* */
 152     ACPI_VARIABLE_LENGTH,           /* 0D PinFunction */
 153     ACPI_VARIABLE_LENGTH,           /* 0E *SerialBus */
 154     ACPI_VARIABLE_LENGTH,           /* 0F PinConfig */
 155     ACPI_VARIABLE_LENGTH,           /* 10 PinGroup */
 156     ACPI_VARIABLE_LENGTH,           /* 11 PinGroupFunction */
 157     ACPI_VARIABLE_LENGTH,           /* 12 PinGroupConfig */
 158 };
 159
 160
 161 /*******************************************************************************
 162  *
 163  * FUNCTION:    AcpiUtWalkAmlResources
 164  *
 165  * PARAMETERS:  WalkState           - Current walk info
 166  * PARAMETERS:  Aml                 - Pointer to the raw AML resource template
 167  *              AmlLength           - Length of the entire template
 168  *              UserFunction        - Called once for each descriptor found. If
 169  *                                    NULL, a pointer to the EndTag is returned
 170  *              Context             - Passed to UserFunction
 171  *
 172  * RETURN:      Status
 173  *
 174  * DESCRIPTION: Walk a raw AML resource list(buffer). User function called
 175  *              once for each resource found.
 176  *
 177  ******************************************************************************/
 178
 179 ACPI_STATUS
 180 AcpiUtWalkAmlResources (
 181     ACPI_WALK_STATE         *WalkState,
 182     UINT8                   *Aml,
 183     ACPI_SIZE               AmlLength,
 184     ACPI_WALK_AML_CALLBACK  UserFunction,
 185     void                    **Context)
 186 {
 187     ACPI_STATUS             Status;
 188     UINT8                   *EndAml;
 189     UINT8                   ResourceIndex;
 190     UINT32                  Length;
 191     UINT32                  Offset = 0;
 192     UINT8                   EndTag[2] = {0x79, 0x00};
 193
 194
 195     ACPI_FUNCTION_TRACE (UtWalkAmlResources);
 196
 197
 198     /*
 199      * The absolute minimum resource template is one EndTag descriptor.
 200      * However, we will treat a lone EndTag as just a simple buffer.
 201      */
 202     if (AmlLength <= sizeof (AML_RESOURCE_END_TAG))
 203     {
 204         return_ACPI_STATUS (AE_AML_NO_RESOURCE_END_TAG);
 205     }
 206
 207     /* Point to the end of the resource template buffer */
 208
 209     EndAml = Aml + AmlLength;
 210
 211     /* Walk the byte list, abort on any invalid descriptor type or length */
 212
 213     while (Aml < EndAml)
 214     {
 215         /* Validate the Resource Type and Resource Length */
 216
 217         Status = AcpiUtValidateResource (WalkState, Aml, &ResourceIndex);
 218         if (ACPI_FAILURE (Status))
 219         {
 220             /*
 221              * Exit on failure. Cannot continue because the descriptor
 222              * length may be bogus also.
 223              */
 224             return_ACPI_STATUS (Status);
 225         }
 226
 227         /* Get the length of this descriptor */
 228
 229         Length = AcpiUtGetDescriptorLength (Aml);
 230
 231         /* Invoke the user function */
 232
 233         if (UserFunction)
 234         {
 235             Status = UserFunction (
 236                 Aml, Length, Offset, ResourceIndex, Context);
 237             if (ACPI_FAILURE (Status))
 238             {
 239                 return_ACPI_STATUS (Status);
 240             }
 241         }
 242
 243         /* An EndTag descriptor terminates this resource template */
 244
 245         if (AcpiUtGetResourceType (Aml) == ACPI_RESOURCE_NAME_END_TAG)
 246         {
 247             /*
 248              * There must be at least one more byte in the buffer for
 249              * the 2nd byte of the EndTag
 250              */
 251             if ((Aml + 1) >= EndAml)
 252             {
 253                 return_ACPI_STATUS (AE_AML_NO_RESOURCE_END_TAG);
 254             }
 255
 256             /*
 257              * The EndTag opcode must be followed by a zero byte.
 258              * Although this byte is technically defined to be a checksum,
 259              * in practice, all ASL compilers set this byte to zero.
 260              */
 261             if (*(Aml + 1) != 0)
 262             {
 263                 return_ACPI_STATUS (AE_AML_NO_RESOURCE_END_TAG);
 264             }
 265
 266             /* Return the pointer to the EndTag if requested */
 267
 268             if (!UserFunction)
 269             {
 270                 *Context = Aml;
 271             }
 272
 273             /*
 274              * Normal exit. Note: We allow the buffer to be larger than
 275              * the resource template, as long as the END_TAG exists.
 276              */
 277             return_ACPI_STATUS (AE_OK);
 278         }
 279
 280         Aml += Length;
 281         Offset += Length;
 282     }
 283
 284     /* Did not find an EndTag descriptor */
 285
 286     if (UserFunction)
 287     {
 288         /* Insert an EndTag anyway. AcpiRsGetListLength always leaves room */
 289
 290         (void) AcpiUtValidateResource (WalkState, EndTag, &ResourceIndex);
 291         Status = UserFunction (EndTag, 2, Offset, ResourceIndex, Context);
 292         if (ACPI_FAILURE (Status))
 293         {
 294             return_ACPI_STATUS (Status);
 295         }
 296     }
 297
 298     return_ACPI_STATUS (AE_AML_NO_RESOURCE_END_TAG);
 299 }
 300
 301
 302 /*******************************************************************************
 303  *
 304  * FUNCTION:    AcpiUtValidateResource
 305  *
 306  * PARAMETERS:  WalkState           - Current walk info
 307  *              Aml                 - Pointer to the raw AML resource descriptor
 308  *              ReturnIndex         - Where the resource index is returned. NULL
 309  *                                    if the index is not required.
 310  *
 311  * RETURN:      Status, and optionally the Index into the global resource tables
 312  *
 313  * DESCRIPTION: Validate an AML resource descriptor by checking the Resource
 314  *              Type and Resource Length. Returns an index into the global
 315  *              resource information/dispatch tables for later use.
 316  *
 317  ******************************************************************************/
 318
 319 ACPI_STATUS
 320 AcpiUtValidateResource (
 321     ACPI_WALK_STATE         *WalkState,
 322     void                    *Aml,
 323     UINT8                   *ReturnIndex)
 324 {
 325     AML_RESOURCE            *AmlResource;
 326     UINT8                   ResourceType;
 327     UINT8                   ResourceIndex;
 328     ACPI_RS_LENGTH          ResourceLength;
 329     ACPI_RS_LENGTH          MinimumResourceLength;
 330
 331
 332     ACPI_FUNCTION_ENTRY ();
 333
 334
 335     /*
 336      * 1) Validate the ResourceType field (Byte 0)
 337      */
 338     ResourceType = ACPI_GET8 (Aml);
 339
 340     /*
 341      * Byte 0 contains the descriptor name (Resource Type)
 342      * Examine the large/small bit in the resource header
 343      */
 344     if (ResourceType & ACPI_RESOURCE_NAME_LARGE)
 345     {
 346         /* Verify the large resource type (name) against the max */
 347
 348         if (ResourceType > ACPI_RESOURCE_NAME_LARGE_MAX)
 349         {
 350             goto InvalidResource;
 351         }
 352
 353         /*
 354          * Large Resource Type -- bits 6:0 contain the name
 355          * Translate range 0x80-0x8B to index range 0x10-0x1B
 356          */
 357         ResourceIndex = (UINT8) (ResourceType - 0x70);
 358     }
 359     else
 360     {
 361         /*
 362          * Small Resource Type -- bits 6:3 contain the name
 363          * Shift range to index range 0x00-0x0F
 364          */
 365         ResourceIndex = (UINT8)
 366             ((ResourceType & ACPI_RESOURCE_NAME_SMALL_MASK) >> 3);
 367     }
 368
 369     /*
 370      * Check validity of the resource type, via AcpiGbl_ResourceTypes.
 371      * Zero indicates an invalid resource.
 372      */
 373     if (!AcpiGbl_ResourceTypes[ResourceIndex])
 374     {
 375         goto InvalidResource;
 376     }
 377
 378     /*
 379      * Validate the ResourceLength field. This ensures that the length
 380      * is at least reasonable, and guarantees that it is non-zero.
 381      */
 382     ResourceLength = AcpiUtGetResourceLength (Aml);
 383     MinimumResourceLength = AcpiGbl_ResourceAmlSizes[ResourceIndex];
 384
 385     /* Validate based upon the type of resource - fixed length or variable */
 386
 387     switch (AcpiGbl_ResourceTypes[ResourceIndex])
 388     {
 389     case ACPI_FIXED_LENGTH:
 390
 391         /* Fixed length resource, length must match exactly */
 392
 393         if (ResourceLength != MinimumResourceLength)
 394         {
 395             goto BadResourceLength;
 396         }
 397         break;
 398
 399     case ACPI_VARIABLE_LENGTH:
 400
 401         /* Variable length resource, length must be at least the minimum */
 402
 403         if (ResourceLength < MinimumResourceLength)
 404         {
 405             goto BadResourceLength;
 406         }
 407         break;
 408
 409     case ACPI_SMALL_VARIABLE_LENGTH:
 410
 411         /* Small variable length resource, length can be (Min) or (Min-1) */
 412
 413         if ((ResourceLength > MinimumResourceLength) ||
 414             (ResourceLength < (MinimumResourceLength - 1)))
 415         {
 416             goto BadResourceLength;
 417         }
 418         break;
 419
 420     default:
 421
 422         /* Shouldn't happen (because of validation earlier), but be sure */
 423
 424         goto InvalidResource;
 425     }
 426
 427     AmlResource = ACPI_CAST_PTR (AML_RESOURCE, Aml);
 428     if (ResourceType == ACPI_RESOURCE_NAME_SERIAL_BUS)
 429     {
 430         /* Validate the BusType field */
 431
 432         if ((AmlResource->CommonSerialBus.Type == 0) ||
 433             (AmlResource->CommonSerialBus.Type > AML_RESOURCE_MAX_SERIALBUSTYPE))
 434         {
 435             if (WalkState)
 436             {
 437                 ACPI_ERROR ((AE_INFO,
 438                     "Invalid/unsupported SerialBus resource descriptor: BusType 0x%2.2X",
 439                     AmlResource->CommonSerialBus.Type));
 440             }
 441             return (AE_AML_INVALID_RESOURCE_TYPE);
 442         }
 443     }
 444
 445     /* Optionally return the resource table index */
 446
 447     if (ReturnIndex)
 448     {
 449         *ReturnIndex = ResourceIndex;
 450     }
 451
 452     return (AE_OK);
 453
 454
 455 InvalidResource:
 456
 457     if (WalkState)
 458     {
 459         ACPI_ERROR ((AE_INFO,
 460             "Invalid/unsupported resource descriptor: Type 0x%2.2X",
 461             ResourceType));
 462     }
 463     return (AE_AML_INVALID_RESOURCE_TYPE);
 464
 465 BadResourceLength:
 466
 467     if (WalkState)
 468     {
 469         ACPI_ERROR ((AE_INFO,
 470             "Invalid resource descriptor length: Type "
 471             "0x%2.2X, Length 0x%4.4X, MinLength 0x%4.4X",
 472             ResourceType, ResourceLength, MinimumResourceLength));
 473     }
 474     return (AE_AML_BAD_RESOURCE_LENGTH);
 475 }
 476
 477
 478 /*******************************************************************************
 479  *
 480  * FUNCTION:    AcpiUtGetResourceType
 481  *
 482  * PARAMETERS:  Aml             - Pointer to the raw AML resource descriptor
 483  *
 484  * RETURN:      The Resource Type with no extraneous bits (except the
 485  *              Large/Small descriptor bit -- this is left alone)
 486  *
 487  * DESCRIPTION: Extract the Resource Type/Name from the first byte of
 488  *              a resource descriptor.
 489  *
 490  ******************************************************************************/
 491
 492 UINT8
 493 AcpiUtGetResourceType (
 494     void                    *Aml)
 495 {
 496     ACPI_FUNCTION_ENTRY ();
 497
 498
 499     /*
 500      * Byte 0 contains the descriptor name (Resource Type)
 501      * Examine the large/small bit in the resource header
 502      */
 503     if (ACPI_GET8 (Aml) & ACPI_RESOURCE_NAME_LARGE)
 504     {
 505         /* Large Resource Type -- bits 6:0 contain the name */
 506
 507         return (ACPI_GET8 (Aml));
 508     }
 509     else
 510     {
 511         /* Small Resource Type -- bits 6:3 contain the name */
 512
 513         return ((UINT8) (ACPI_GET8 (Aml) & ACPI_RESOURCE_NAME_SMALL_MASK));
 514     }
 515 }
 516
 517
 518 /*******************************************************************************
 519  *
 520  * FUNCTION:    AcpiUtGetResourceLength
 521  *
 522  * PARAMETERS:  Aml             - Pointer to the raw AML resource descriptor
 523  *
 524  * RETURN:      Byte Length
 525  *
 526  * DESCRIPTION: Get the "Resource Length" of a raw AML descriptor. By
 527  *              definition, this does not include the size of the descriptor
 528  *              header or the length field itself.
 529  *
 530  ******************************************************************************/
 531
 532 UINT16
 533 AcpiUtGetResourceLength (
 534     void                    *Aml)
 535 {
 536     ACPI_RS_LENGTH          ResourceLength;
 537
 538
 539     ACPI_FUNCTION_ENTRY ();
 540
 541
 542     /*
 543      * Byte 0 contains the descriptor name (Resource Type)
 544      * Examine the large/small bit in the resource header
 545      */
 546     if (ACPI_GET8 (Aml) & ACPI_RESOURCE_NAME_LARGE)
 547     {
 548         /* Large Resource type -- bytes 1-2 contain the 16-bit length */
 549
 550         ACPI_MOVE_16_TO_16 (&ResourceLength, ACPI_ADD_PTR (UINT8, Aml, 1));
 551
 552     }
 553     else
 554     {
 555         /* Small Resource type -- bits 2:0 of byte 0 contain the length */
 556
 557         ResourceLength = (UINT16) (ACPI_GET8 (Aml) &
 558             ACPI_RESOURCE_NAME_SMALL_LENGTH_MASK);
 559     }
 560
 561     return (ResourceLength);
 562 }
 563
 564
 565 /*******************************************************************************
 566  *
 567  * FUNCTION:    AcpiUtGetResourceHeaderLength
 568  *
 569  * PARAMETERS:  Aml             - Pointer to the raw AML resource descriptor
 570  *
 571  * RETURN:      Length of the AML header (depends on large/small descriptor)
 572  *
 573  * DESCRIPTION: Get the length of the header for this resource.
 574  *
 575  ******************************************************************************/
 576
 577 UINT8
 578 AcpiUtGetResourceHeaderLength (
 579     void                    *Aml)
 580 {
 581     ACPI_FUNCTION_ENTRY ();
 582
 583
 584     /* Examine the large/small bit in the resource header */
 585
 586     if (ACPI_GET8 (Aml) & ACPI_RESOURCE_NAME_LARGE)
 587     {
 588         return (sizeof (AML_RESOURCE_LARGE_HEADER));
 589     }
 590     else
 591     {
 592         return (sizeof (AML_RESOURCE_SMALL_HEADER));
 593     }
 594 }
 595
 596
 597 /*******************************************************************************
 598  *
 599  * FUNCTION:    AcpiUtGetDescriptorLength
 600  *
 601  * PARAMETERS:  Aml             - Pointer to the raw AML resource descriptor
 602  *
 603  * RETURN:      Byte length
 604  *
 605  * DESCRIPTION: Get the total byte length of a raw AML descriptor, including the
 606  *              length of the descriptor header and the length field itself.
 607  *              Used to walk descriptor lists.
 608  *
 609  ******************************************************************************/
 610
 611 UINT32
 612 AcpiUtGetDescriptorLength (
 613     void                    *Aml)
 614 {
 615     ACPI_FUNCTION_ENTRY ();
 616
 617
 618     /*
 619      * Get the Resource Length (does not include header length) and add
 620      * the header length (depends on if this is a small or large resource)
 621      */
 622     return (AcpiUtGetResourceLength (Aml) +
 623         AcpiUtGetResourceHeaderLength (Aml));
 624 }
 625
 626
 627 /*******************************************************************************
 628  *
 629  * FUNCTION:    AcpiUtGetResourceEndTag
 630  *
 631  * PARAMETERS:  ObjDesc         - The resource template buffer object
 632  *              EndTag          - Where the pointer to the EndTag is returned
 633  *
 634  * RETURN:      Status, pointer to the end tag
 635  *
 636  * DESCRIPTION: Find the EndTag resource descriptor in an AML resource template
 637  *              Note: allows a buffer length of zero.
 638  *
 639  ******************************************************************************/
 640
 641 ACPI_STATUS
 642 AcpiUtGetResourceEndTag (
 643     ACPI_OPERAND_OBJECT     *ObjDesc,
 644     UINT8                   **EndTag)
 645 {
 646     ACPI_STATUS             Status;
 647
 648
 649     ACPI_FUNCTION_TRACE (UtGetResourceEndTag);
 650
 651
 652     /* Allow a buffer length of zero */
 653
 654     if (!ObjDesc->Buffer.Length)
 655     {
 656         *EndTag = ObjDesc->Buffer.Pointer;
 657         return_ACPI_STATUS (AE_OK);
 658     }
 659
 660     /* Validate the template and get a pointer to the EndTag */
 661
 662     Status = AcpiUtWalkAmlResources (NULL, ObjDesc->Buffer.Pointer,
 663         ObjDesc->Buffer.Length, NULL, (void **) EndTag);
 664
 665     return_ACPI_STATUS (Status);
 666 }