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nsaccess.c revision 1.1
      1 /*******************************************************************************
      2  *
      3  * Module Name: nsaccess - Top-level functions for accessing ACPI namespace
      4  *
      5  ******************************************************************************/
      6 
      7 /******************************************************************************
      8  *
      9  * 1. Copyright Notice
     10  *
     11  * Some or all of this work - Copyright (c) 1999 - 2010, Intel Corp.
     12  * All rights reserved.
     13  *
     14  * 2. License
     15  *
     16  * 2.1. This is your license from Intel Corp. under its intellectual property
     17  * rights.  You may have additional license terms from the party that provided
     18  * you this software, covering your right to use that party's intellectual
     19  * property rights.
     20  *
     21  * 2.2. Intel grants, free of charge, to any person ("Licensee") obtaining a
     22  * copy of the source code appearing in this file ("Covered Code") an
     23  * irrevocable, perpetual, worldwide license under Intel's copyrights in the
     24  * base code distributed originally by Intel ("Original Intel Code") to copy,
     25  * make derivatives, distribute, use and display any portion of the Covered
     26  * Code in any form, with the right to sublicense such rights; and
     27  *
     28  * 2.3. Intel grants Licensee a non-exclusive and non-transferable patent
     29  * license (with the right to sublicense), under only those claims of Intel
     30  * patents that are infringed by the Original Intel Code, to make, use, sell,
     31  * offer to sell, and import the Covered Code and derivative works thereof
     32  * solely to the minimum extent necessary to exercise the above copyright
     33  * license, and in no event shall the patent license extend to any additions
     34  * to or modifications of the Original Intel Code.  No other license or right
     35  * is granted directly or by implication, estoppel or otherwise;
     36  *
     37  * The above copyright and patent license is granted only if the following
     38  * conditions are met:
     39  *
     40  * 3. Conditions
     41  *
     42  * 3.1. Redistribution of Source with Rights to Further Distribute Source.
     43  * Redistribution of source code of any substantial portion of the Covered
     44  * Code or modification with rights to further distribute source must include
     45  * the above Copyright Notice, the above License, this list of Conditions,
     46  * and the following Disclaimer and Export Compliance provision.  In addition,
     47  * Licensee must cause all Covered Code to which Licensee contributes to
     48  * contain a file documenting the changes Licensee made to create that Covered
     49  * Code and the date of any change.  Licensee must include in that file the
     50  * documentation of any changes made by any predecessor Licensee.  Licensee
     51  * must include a prominent statement that the modification is derived,
     52  * directly or indirectly, from Original Intel Code.
     53  *
     54  * 3.2. Redistribution of Source with no Rights to Further Distribute Source.
     55  * Redistribution of source code of any substantial portion of the Covered
     56  * Code or modification without rights to further distribute source must
     57  * include the following Disclaimer and Export Compliance provision in the
     58  * documentation and/or other materials provided with distribution.  In
     59  * addition, Licensee may not authorize further sublicense of source of any
     60  * portion of the Covered Code, and must include terms to the effect that the
     61  * license from Licensee to its licensee is limited to the intellectual
     62  * property embodied in the software Licensee provides to its licensee, and
     63  * not to intellectual property embodied in modifications its licensee may
     64  * make.
     65  *
     66  * 3.3. Redistribution of Executable. Redistribution in executable form of any
     67  * substantial portion of the Covered Code or modification must reproduce the
     68  * above Copyright Notice, and the following Disclaimer and Export Compliance
     69  * provision in the documentation and/or other materials provided with the
     70  * distribution.
     71  *
     72  * 3.4. Intel retains all right, title, and interest in and to the Original
     73  * Intel Code.
     74  *
     75  * 3.5. Neither the name Intel nor any other trademark owned or controlled by
     76  * Intel shall be used in advertising or otherwise to promote the sale, use or
     77  * other dealings in products derived from or relating to the Covered Code
     78  * without prior written authorization from Intel.
     79  *
     80  * 4. Disclaimer and Export Compliance
     81  *
     82  * 4.1. INTEL MAKES NO WARRANTY OF ANY KIND REGARDING ANY SOFTWARE PROVIDED
     83  * HERE.  ANY SOFTWARE ORIGINATING FROM INTEL OR DERIVED FROM INTEL SOFTWARE
     84  * IS PROVIDED "AS IS," AND INTEL WILL NOT PROVIDE ANY SUPPORT,  ASSISTANCE,
     85  * INSTALLATION, TRAINING OR OTHER SERVICES.  INTEL WILL NOT PROVIDE ANY
     86  * UPDATES, ENHANCEMENTS OR EXTENSIONS.  INTEL SPECIFICALLY DISCLAIMS ANY
     87  * IMPLIED WARRANTIES OF MERCHANTABILITY, NONINFRINGEMENT AND FITNESS FOR A
     88  * PARTICULAR PURPOSE.
     89  *
     90  * 4.2. IN NO EVENT SHALL INTEL HAVE ANY LIABILITY TO LICENSEE, ITS LICENSEES
     91  * OR ANY OTHER THIRD PARTY, FOR ANY LOST PROFITS, LOST DATA, LOSS OF USE OR
     92  * COSTS OF PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES, OR FOR ANY INDIRECT,
     93  * SPECIAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THIS AGREEMENT, UNDER ANY
     94  * CAUSE OF ACTION OR THEORY OF LIABILITY, AND IRRESPECTIVE OF WHETHER INTEL
     95  * HAS ADVANCE NOTICE OF THE POSSIBILITY OF SUCH DAMAGES.  THESE LIMITATIONS
     96  * SHALL APPLY NOTWITHSTANDING THE FAILURE OF THE ESSENTIAL PURPOSE OF ANY
     97  * LIMITED REMEDY.
     98  *
     99  * 4.3. Licensee shall not export, either directly or indirectly, any of this
    100  * software or system incorporating such software without first obtaining any
    101  * required license or other approval from the U. S. Department of Commerce or
    102  * any other agency or department of the United States Government.  In the
    103  * event Licensee exports any such software from the United States or
    104  * re-exports any such software from a foreign destination, Licensee shall
    105  * ensure that the distribution and export/re-export of the software is in
    106  * compliance with all laws, regulations, orders, or other restrictions of the
    107  * U.S. Export Administration Regulations. Licensee agrees that neither it nor
    108  * any of its subsidiaries will export/re-export any technical data, process,
    109  * software, or service, directly or indirectly, to any country for which the
    110  * United States government or any agency thereof requires an export license,
    111  * other governmental approval, or letter of assurance, without first obtaining
    112  * such license, approval or letter.
    113  *
    114  *****************************************************************************/
    115 
    116 #define __NSACCESS_C__
    117 
    118 #include "acpi.h"
    119 #include "accommon.h"
    120 #include "amlcode.h"
    121 #include "acnamesp.h"
    122 #include "acdispat.h"
    123 
    124 
    125 #define _COMPONENT          ACPI_NAMESPACE
    126         ACPI_MODULE_NAME    ("nsaccess")
    127 
    128 
    129 /*******************************************************************************
    130  *
    131  * FUNCTION:    AcpiNsRootInitialize
    132  *
    133  * PARAMETERS:  None
    134  *
    135  * RETURN:      Status
    136  *
    137  * DESCRIPTION: Allocate and initialize the default root named objects
    138  *
    139  * MUTEX:       Locks namespace for entire execution
    140  *
    141  ******************************************************************************/
    142 
    143 ACPI_STATUS
    144 AcpiNsRootInitialize (
    145     void)
    146 {
    147     ACPI_STATUS                 Status;
    148     const ACPI_PREDEFINED_NAMES *InitVal = NULL;
    149     ACPI_NAMESPACE_NODE         *NewNode;
    150     ACPI_OPERAND_OBJECT         *ObjDesc;
    151     ACPI_STRING                 Val = NULL;
    152 
    153 
    154     ACPI_FUNCTION_TRACE (NsRootInitialize);
    155 
    156 
    157     Status = AcpiUtAcquireMutex (ACPI_MTX_NAMESPACE);
    158     if (ACPI_FAILURE (Status))
    159     {
    160         return_ACPI_STATUS (Status);
    161     }
    162 
    163     /*
    164      * The global root ptr is initially NULL, so a non-NULL value indicates
    165      * that AcpiNsRootInitialize() has already been called; just return.
    166      */
    167     if (AcpiGbl_RootNode)
    168     {
    169         Status = AE_OK;
    170         goto UnlockAndExit;
    171     }
    172 
    173     /*
    174      * Tell the rest of the subsystem that the root is initialized
    175      * (This is OK because the namespace is locked)
    176      */
    177     AcpiGbl_RootNode = &AcpiGbl_RootNodeStruct;
    178 
    179     /* Enter the pre-defined names in the name table */
    180 
    181     ACPI_DEBUG_PRINT ((ACPI_DB_INFO,
    182         "Entering predefined entries into namespace\n"));
    183 
    184     for (InitVal = AcpiGbl_PreDefinedNames; InitVal->Name; InitVal++)
    185     {
    186         /* _OSI is optional for now, will be permanent later */
    187 
    188         if (!ACPI_STRCMP (InitVal->Name, "_OSI") && !AcpiGbl_CreateOsiMethod)
    189         {
    190             continue;
    191         }
    192 
    193         Status = AcpiNsLookup (NULL, InitVal->Name, InitVal->Type,
    194                         ACPI_IMODE_LOAD_PASS2, ACPI_NS_NO_UPSEARCH,
    195                         NULL, &NewNode);
    196 
    197         if (ACPI_FAILURE (Status) || (!NewNode)) /* Must be on same line for code converter */
    198         {
    199             ACPI_EXCEPTION ((AE_INFO, Status,
    200                 "Could not create predefined name %s",
    201                 InitVal->Name));
    202         }
    203 
    204         /*
    205          * Name entered successfully. If entry in PreDefinedNames[] specifies
    206          * an initial value, create the initial value.
    207          */
    208         if (InitVal->Val)
    209         {
    210             Status = AcpiOsPredefinedOverride (InitVal, &Val);
    211             if (ACPI_FAILURE (Status))
    212             {
    213                 ACPI_ERROR ((AE_INFO,
    214                     "Could not override predefined %s",
    215                     InitVal->Name));
    216             }
    217 
    218             if (!Val)
    219             {
    220                 Val = InitVal->Val;
    221             }
    222 
    223             /*
    224              * Entry requests an initial value, allocate a
    225              * descriptor for it.
    226              */
    227             ObjDesc = AcpiUtCreateInternalObject (InitVal->Type);
    228             if (!ObjDesc)
    229             {
    230                 Status = AE_NO_MEMORY;
    231                 goto UnlockAndExit;
    232             }
    233 
    234             /*
    235              * Convert value string from table entry to
    236              * internal representation. Only types actually
    237              * used for initial values are implemented here.
    238              */
    239             switch (InitVal->Type)
    240             {
    241             case ACPI_TYPE_METHOD:
    242                 ObjDesc->Method.ParamCount = (UINT8) ACPI_TO_INTEGER (Val);
    243                 ObjDesc->Common.Flags |= AOPOBJ_DATA_VALID;
    244 
    245 #if defined (ACPI_ASL_COMPILER)
    246 
    247                 /* Save the parameter count for the iASL compiler */
    248 
    249                 NewNode->Value = ObjDesc->Method.ParamCount;
    250 #else
    251                 /* Mark this as a very SPECIAL method */
    252 
    253                 ObjDesc->Method.MethodFlags = AML_METHOD_INTERNAL_ONLY;
    254                 ObjDesc->Method.Extra.Implementation = AcpiUtOsiImplementation;
    255 #endif
    256                 break;
    257 
    258             case ACPI_TYPE_INTEGER:
    259 
    260                 ObjDesc->Integer.Value = ACPI_TO_INTEGER (Val);
    261                 break;
    262 
    263 
    264             case ACPI_TYPE_STRING:
    265 
    266                 /* Build an object around the static string */
    267 
    268                 ObjDesc->String.Length = (UINT32) ACPI_STRLEN (Val);
    269                 ObjDesc->String.Pointer = Val;
    270                 ObjDesc->Common.Flags |= AOPOBJ_STATIC_POINTER;
    271                 break;
    272 
    273 
    274             case ACPI_TYPE_MUTEX:
    275 
    276                 ObjDesc->Mutex.Node = NewNode;
    277                 ObjDesc->Mutex.SyncLevel = (UINT8) (ACPI_TO_INTEGER (Val) - 1);
    278 
    279                 /* Create a mutex */
    280 
    281                 Status = AcpiOsCreateMutex (&ObjDesc->Mutex.OsMutex);
    282                 if (ACPI_FAILURE (Status))
    283                 {
    284                     AcpiUtRemoveReference (ObjDesc);
    285                     goto UnlockAndExit;
    286                 }
    287 
    288                 /* Special case for ACPI Global Lock */
    289 
    290                 if (ACPI_STRCMP (InitVal->Name, "_GL_") == 0)
    291                 {
    292                     AcpiGbl_GlobalLockMutex = ObjDesc;
    293 
    294                     /* Create additional counting semaphore for global lock */
    295 
    296                     Status = AcpiOsCreateSemaphore (
    297                                 1, 0, &AcpiGbl_GlobalLockSemaphore);
    298                     if (ACPI_FAILURE (Status))
    299                     {
    300                         AcpiUtRemoveReference (ObjDesc);
    301                         goto UnlockAndExit;
    302                     }
    303                 }
    304                 break;
    305 
    306 
    307             default:
    308 
    309                 ACPI_ERROR ((AE_INFO, "Unsupported initial type value 0x%X",
    310                     InitVal->Type));
    311                 AcpiUtRemoveReference (ObjDesc);
    312                 ObjDesc = NULL;
    313                 continue;
    314             }
    315 
    316             /* Store pointer to value descriptor in the Node */
    317 
    318             Status = AcpiNsAttachObject (NewNode, ObjDesc,
    319                         ObjDesc->Common.Type);
    320 
    321             /* Remove local reference to the object */
    322 
    323             AcpiUtRemoveReference (ObjDesc);
    324         }
    325     }
    326 
    327 
    328 UnlockAndExit:
    329     (void) AcpiUtReleaseMutex (ACPI_MTX_NAMESPACE);
    330 
    331     /* Save a handle to "_GPE", it is always present */
    332 
    333     if (ACPI_SUCCESS (Status))
    334     {
    335         Status = AcpiNsGetNode (NULL, "\\_GPE", ACPI_NS_NO_UPSEARCH,
    336                     &AcpiGbl_FadtGpeDevice);
    337     }
    338 
    339     return_ACPI_STATUS (Status);
    340 }
    341 
    342 
    343 /*******************************************************************************
    344  *
    345  * FUNCTION:    AcpiNsLookup
    346  *
    347  * PARAMETERS:  ScopeInfo       - Current scope info block
    348  *              Pathname        - Search pathname, in internal format
    349  *                                (as represented in the AML stream)
    350  *              Type            - Type associated with name
    351  *              InterpreterMode - IMODE_LOAD_PASS2 => add name if not found
    352  *              Flags           - Flags describing the search restrictions
    353  *              WalkState       - Current state of the walk
    354  *              ReturnNode      - Where the Node is placed (if found
    355  *                                or created successfully)
    356  *
    357  * RETURN:      Status
    358  *
    359  * DESCRIPTION: Find or enter the passed name in the name space.
    360  *              Log an error if name not found in Exec mode.
    361  *
    362  * MUTEX:       Assumes namespace is locked.
    363  *
    364  ******************************************************************************/
    365 
    366 ACPI_STATUS
    367 AcpiNsLookup (
    368     ACPI_GENERIC_STATE      *ScopeInfo,
    369     char                    *Pathname,
    370     ACPI_OBJECT_TYPE        Type,
    371     ACPI_INTERPRETER_MODE   InterpreterMode,
    372     UINT32                  Flags,
    373     ACPI_WALK_STATE         *WalkState,
    374     ACPI_NAMESPACE_NODE     **ReturnNode)
    375 {
    376     ACPI_STATUS             Status;
    377     char                    *Path = Pathname;
    378     ACPI_NAMESPACE_NODE     *PrefixNode;
    379     ACPI_NAMESPACE_NODE     *CurrentNode = NULL;
    380     ACPI_NAMESPACE_NODE     *ThisNode = NULL;
    381     UINT32                  NumSegments;
    382     UINT32                  NumCarats;
    383     ACPI_NAME               SimpleName;
    384     ACPI_OBJECT_TYPE        TypeToCheckFor;
    385     ACPI_OBJECT_TYPE        ThisSearchType;
    386     UINT32                  SearchParentFlag = ACPI_NS_SEARCH_PARENT;
    387     UINT32                  LocalFlags;
    388 
    389 
    390     ACPI_FUNCTION_TRACE (NsLookup);
    391 
    392 
    393     if (!ReturnNode)
    394     {
    395         return_ACPI_STATUS (AE_BAD_PARAMETER);
    396     }
    397 
    398     LocalFlags = Flags & ~(ACPI_NS_ERROR_IF_FOUND | ACPI_NS_SEARCH_PARENT);
    399     *ReturnNode = ACPI_ENTRY_NOT_FOUND;
    400     AcpiGbl_NsLookupCount++;
    401 
    402     if (!AcpiGbl_RootNode)
    403     {
    404         return_ACPI_STATUS (AE_NO_NAMESPACE);
    405     }
    406 
    407     /* Get the prefix scope. A null scope means use the root scope */
    408 
    409     if ((!ScopeInfo) ||
    410         (!ScopeInfo->Scope.Node))
    411     {
    412         ACPI_DEBUG_PRINT ((ACPI_DB_NAMES,
    413             "Null scope prefix, using root node (%p)\n",
    414             AcpiGbl_RootNode));
    415 
    416         PrefixNode = AcpiGbl_RootNode;
    417     }
    418     else
    419     {
    420         PrefixNode = ScopeInfo->Scope.Node;
    421         if (ACPI_GET_DESCRIPTOR_TYPE (PrefixNode) != ACPI_DESC_TYPE_NAMED)
    422         {
    423             ACPI_ERROR ((AE_INFO, "%p is not a namespace node [%s]",
    424                 PrefixNode, AcpiUtGetDescriptorName (PrefixNode)));
    425             return_ACPI_STATUS (AE_AML_INTERNAL);
    426         }
    427 
    428         if (!(Flags & ACPI_NS_PREFIX_IS_SCOPE))
    429         {
    430             /*
    431              * This node might not be a actual "scope" node (such as a
    432              * Device/Method, etc.)  It could be a Package or other object
    433              * node. Backup up the tree to find the containing scope node.
    434              */
    435             while (!AcpiNsOpensScope (PrefixNode->Type) &&
    436                     PrefixNode->Type != ACPI_TYPE_ANY)
    437             {
    438                 PrefixNode = PrefixNode->Parent;
    439             }
    440         }
    441     }
    442 
    443     /* Save type. TBD: may be no longer necessary */
    444 
    445     TypeToCheckFor = Type;
    446 
    447     /*
    448      * Begin examination of the actual pathname
    449      */
    450     if (!Pathname)
    451     {
    452         /* A Null NamePath is allowed and refers to the root */
    453 
    454         NumSegments = 0;
    455         ThisNode = AcpiGbl_RootNode;
    456         Path = "";
    457 
    458         ACPI_DEBUG_PRINT ((ACPI_DB_NAMES,
    459             "Null Pathname (Zero segments), Flags=%X\n", Flags));
    460     }
    461     else
    462     {
    463         /*
    464          * Name pointer is valid (and must be in internal name format)
    465          *
    466          * Check for scope prefixes:
    467          *
    468          * As represented in the AML stream, a namepath consists of an
    469          * optional scope prefix followed by a name segment part.
    470          *
    471          * If present, the scope prefix is either a Root Prefix (in
    472          * which case the name is fully qualified), or one or more
    473          * Parent Prefixes (in which case the name's scope is relative
    474          * to the current scope).
    475          */
    476         if (*Path == (UINT8) AML_ROOT_PREFIX)
    477         {
    478             /* Pathname is fully qualified, start from the root */
    479 
    480             ThisNode = AcpiGbl_RootNode;
    481             SearchParentFlag = ACPI_NS_NO_UPSEARCH;
    482 
    483             /* Point to name segment part */
    484 
    485             Path++;
    486 
    487             ACPI_DEBUG_PRINT ((ACPI_DB_NAMES,
    488                 "Path is absolute from root [%p]\n", ThisNode));
    489         }
    490         else
    491         {
    492             /* Pathname is relative to current scope, start there */
    493 
    494             ACPI_DEBUG_PRINT ((ACPI_DB_NAMES,
    495                 "Searching relative to prefix scope [%4.4s] (%p)\n",
    496                 AcpiUtGetNodeName (PrefixNode), PrefixNode));
    497 
    498             /*
    499              * Handle multiple Parent Prefixes (carat) by just getting
    500              * the parent node for each prefix instance.
    501              */
    502             ThisNode = PrefixNode;
    503             NumCarats = 0;
    504             while (*Path == (UINT8) AML_PARENT_PREFIX)
    505             {
    506                 /* Name is fully qualified, no search rules apply */
    507 
    508                 SearchParentFlag = ACPI_NS_NO_UPSEARCH;
    509 
    510                 /*
    511                  * Point past this prefix to the name segment
    512                  * part or the next Parent Prefix
    513                  */
    514                 Path++;
    515 
    516                 /* Backup to the parent node */
    517 
    518                 NumCarats++;
    519                 ThisNode = ThisNode->Parent;
    520                 if (!ThisNode)
    521                 {
    522                     /* Current scope has no parent scope */
    523 
    524                     ACPI_ERROR ((AE_INFO,
    525                         "ACPI path has too many parent prefixes (^) "
    526                         "- reached beyond root node"));
    527                     return_ACPI_STATUS (AE_NOT_FOUND);
    528                 }
    529             }
    530 
    531             if (SearchParentFlag == ACPI_NS_NO_UPSEARCH)
    532             {
    533                 ACPI_DEBUG_PRINT ((ACPI_DB_NAMES,
    534                     "Search scope is [%4.4s], path has %u carat(s)\n",
    535                     AcpiUtGetNodeName (ThisNode), NumCarats));
    536             }
    537         }
    538 
    539         /*
    540          * Determine the number of ACPI name segments in this pathname.
    541          *
    542          * The segment part consists of either:
    543          *  - A Null name segment (0)
    544          *  - A DualNamePrefix followed by two 4-byte name segments
    545          *  - A MultiNamePrefix followed by a byte indicating the
    546          *      number of segments and the segments themselves.
    547          *  - A single 4-byte name segment
    548          *
    549          * Examine the name prefix opcode, if any, to determine the number of
    550          * segments.
    551          */
    552         switch (*Path)
    553         {
    554         case 0:
    555             /*
    556              * Null name after a root or parent prefixes. We already
    557              * have the correct target node and there are no name segments.
    558              */
    559             NumSegments  = 0;
    560             Type = ThisNode->Type;
    561 
    562             ACPI_DEBUG_PRINT ((ACPI_DB_NAMES,
    563                 "Prefix-only Pathname (Zero name segments), Flags=%X\n",
    564                 Flags));
    565             break;
    566 
    567         case AML_DUAL_NAME_PREFIX:
    568 
    569             /* More than one NameSeg, search rules do not apply */
    570 
    571             SearchParentFlag = ACPI_NS_NO_UPSEARCH;
    572 
    573             /* Two segments, point to first name segment */
    574 
    575             NumSegments = 2;
    576             Path++;
    577 
    578             ACPI_DEBUG_PRINT ((ACPI_DB_NAMES,
    579                 "Dual Pathname (2 segments, Flags=%X)\n", Flags));
    580             break;
    581 
    582         case AML_MULTI_NAME_PREFIX_OP:
    583 
    584             /* More than one NameSeg, search rules do not apply */
    585 
    586             SearchParentFlag = ACPI_NS_NO_UPSEARCH;
    587 
    588             /* Extract segment count, point to first name segment */
    589 
    590             Path++;
    591             NumSegments = (UINT32) (UINT8) *Path;
    592             Path++;
    593 
    594             ACPI_DEBUG_PRINT ((ACPI_DB_NAMES,
    595                 "Multi Pathname (%u Segments, Flags=%X)\n",
    596                 NumSegments, Flags));
    597             break;
    598 
    599         default:
    600             /*
    601              * Not a Null name, no Dual or Multi prefix, hence there is
    602              * only one name segment and Pathname is already pointing to it.
    603              */
    604             NumSegments = 1;
    605 
    606             ACPI_DEBUG_PRINT ((ACPI_DB_NAMES,
    607                 "Simple Pathname (1 segment, Flags=%X)\n", Flags));
    608             break;
    609         }
    610 
    611         ACPI_DEBUG_EXEC (AcpiNsPrintPathname (NumSegments, Path));
    612     }
    613 
    614 
    615     /*
    616      * Search namespace for each segment of the name. Loop through and
    617      * verify (or add to the namespace) each name segment.
    618      *
    619      * The object type is significant only at the last name
    620      * segment. (We don't care about the types along the path, only
    621      * the type of the final target object.)
    622      */
    623     ThisSearchType = ACPI_TYPE_ANY;
    624     CurrentNode = ThisNode;
    625     while (NumSegments && CurrentNode)
    626     {
    627         NumSegments--;
    628         if (!NumSegments)
    629         {
    630             /* This is the last segment, enable typechecking */
    631 
    632             ThisSearchType = Type;
    633 
    634             /*
    635              * Only allow automatic parent search (search rules) if the caller
    636              * requested it AND we have a single, non-fully-qualified NameSeg
    637              */
    638             if ((SearchParentFlag != ACPI_NS_NO_UPSEARCH) &&
    639                 (Flags & ACPI_NS_SEARCH_PARENT))
    640             {
    641                 LocalFlags |= ACPI_NS_SEARCH_PARENT;
    642             }
    643 
    644             /* Set error flag according to caller */
    645 
    646             if (Flags & ACPI_NS_ERROR_IF_FOUND)
    647             {
    648                 LocalFlags |= ACPI_NS_ERROR_IF_FOUND;
    649             }
    650         }
    651 
    652         /* Extract one ACPI name from the front of the pathname */
    653 
    654         ACPI_MOVE_32_TO_32 (&SimpleName, Path);
    655 
    656         /* Try to find the single (4 character) ACPI name */
    657 
    658         Status = AcpiNsSearchAndEnter (SimpleName, WalkState, CurrentNode,
    659                     InterpreterMode, ThisSearchType, LocalFlags, &ThisNode);
    660         if (ACPI_FAILURE (Status))
    661         {
    662             if (Status == AE_NOT_FOUND)
    663             {
    664                 /* Name not found in ACPI namespace */
    665 
    666                 ACPI_DEBUG_PRINT ((ACPI_DB_NAMES,
    667                     "Name [%4.4s] not found in scope [%4.4s] %p\n",
    668                     (char *) &SimpleName, (char *) &CurrentNode->Name,
    669                     CurrentNode));
    670             }
    671 
    672             *ReturnNode = ThisNode;
    673             return_ACPI_STATUS (Status);
    674         }
    675 
    676         /* More segments to follow? */
    677 
    678         if (NumSegments > 0)
    679         {
    680             /*
    681              * If we have an alias to an object that opens a scope (such as a
    682              * device or processor), we need to dereference the alias here so
    683              * that we can access any children of the original node (via the
    684              * remaining segments).
    685              */
    686             if (ThisNode->Type == ACPI_TYPE_LOCAL_ALIAS)
    687             {
    688                 if (!ThisNode->Object)
    689                 {
    690                     return_ACPI_STATUS (AE_NOT_EXIST);
    691                 }
    692 
    693                 if (AcpiNsOpensScope (((ACPI_NAMESPACE_NODE *)
    694                         ThisNode->Object)->Type))
    695                 {
    696                     ThisNode = (ACPI_NAMESPACE_NODE *) ThisNode->Object;
    697                 }
    698             }
    699         }
    700 
    701         /* Special handling for the last segment (NumSegments == 0) */
    702 
    703         else
    704         {
    705             /*
    706              * Sanity typecheck of the target object:
    707              *
    708              * If 1) This is the last segment (NumSegments == 0)
    709              *    2) And we are looking for a specific type
    710              *       (Not checking for TYPE_ANY)
    711              *    3) Which is not an alias
    712              *    4) Which is not a local type (TYPE_SCOPE)
    713              *    5) And the type of target object is known (not TYPE_ANY)
    714              *    6) And target object does not match what we are looking for
    715              *
    716              * Then we have a type mismatch. Just warn and ignore it.
    717              */
    718             if ((TypeToCheckFor != ACPI_TYPE_ANY)                   &&
    719                 (TypeToCheckFor != ACPI_TYPE_LOCAL_ALIAS)           &&
    720                 (TypeToCheckFor != ACPI_TYPE_LOCAL_METHOD_ALIAS)    &&
    721                 (TypeToCheckFor != ACPI_TYPE_LOCAL_SCOPE)           &&
    722                 (ThisNode->Type != ACPI_TYPE_ANY)                   &&
    723                 (ThisNode->Type != TypeToCheckFor))
    724             {
    725                 /* Complain about a type mismatch */
    726 
    727                 ACPI_WARNING ((AE_INFO,
    728                     "NsLookup: Type mismatch on %4.4s (%s), searching for (%s)",
    729                     ACPI_CAST_PTR (char, &SimpleName),
    730                     AcpiUtGetTypeName (ThisNode->Type),
    731                     AcpiUtGetTypeName (TypeToCheckFor)));
    732             }
    733 
    734             /*
    735              * If this is the last name segment and we are not looking for a
    736              * specific type, but the type of found object is known, use that
    737              * type to (later) see if it opens a scope.
    738              */
    739             if (Type == ACPI_TYPE_ANY)
    740             {
    741                 Type = ThisNode->Type;
    742             }
    743         }
    744 
    745         /* Point to next name segment and make this node current */
    746 
    747         Path += ACPI_NAME_SIZE;
    748         CurrentNode = ThisNode;
    749     }
    750 
    751     /* Always check if we need to open a new scope */
    752 
    753     if (!(Flags & ACPI_NS_DONT_OPEN_SCOPE) && (WalkState))
    754     {
    755         /*
    756          * If entry is a type which opens a scope, push the new scope on the
    757          * scope stack.
    758          */
    759         if (AcpiNsOpensScope (Type))
    760         {
    761             Status = AcpiDsScopeStackPush (ThisNode, Type, WalkState);
    762             if (ACPI_FAILURE (Status))
    763             {
    764                 return_ACPI_STATUS (Status);
    765             }
    766         }
    767     }
    768 
    769     *ReturnNode = ThisNode;
    770     return_ACPI_STATUS (AE_OK);
    771 }
    772 
    773