nsaccess.c

acpi tools for linux include acpiexec and acpixtract

    ACPI_NAME               SimpleName;
    ACPI_OBJECT_TYPE        TypeToCheckFor;
    ACPI_OBJECT_TYPE        ThisSearchType;
    UINT32                  SearchParentFlag = ACPI_NS_SEARCH_PARENT;
    UINT32                  LocalFlags;


    ACPI_FUNCTION_TRACE (NsLookup);


    if (!ReturnNode)
    {
        return_ACPI_STATUS (AE_BAD_PARAMETER);
    }

    LocalFlags = Flags & ~(ACPI_NS_ERROR_IF_FOUND | ACPI_NS_SEARCH_PARENT);
    *ReturnNode = ACPI_ENTRY_NOT_FOUND;
    AcpiGbl_NsLookupCount++;

    if (!AcpiGbl_RootNode)
    {
        return_ACPI_STATUS (AE_NO_NAMESPACE);
    }

    /*
     * Get the prefix scope.
     * A null scope means use the root scope
     */
    if ((!ScopeInfo) ||
        (!ScopeInfo->Scope.Node))
    {
        ACPI_DEBUG_PRINT ((ACPI_DB_NAMES,
            "Null scope prefix, using root node (%p)\n",
            AcpiGbl_RootNode));

        PrefixNode = AcpiGbl_RootNode;
    }
    else
    {
        PrefixNode = ScopeInfo->Scope.Node;
        if (ACPI_GET_DESCRIPTOR_TYPE (PrefixNode) != ACPI_DESC_TYPE_NAMED)
        {
            ACPI_ERROR ((AE_INFO, "%p is not a namespace node [%s]",
                PrefixNode, AcpiUtGetDescriptorName (PrefixNode)));
            return_ACPI_STATUS (AE_AML_INTERNAL);
        }

        if (!(Flags & ACPI_NS_PREFIX_IS_SCOPE))
        {
            /*
             * This node might not be a actual "scope" node (such as a
             * Device/Method, etc.)  It could be a Package or other object node.
             * Backup up the tree to find the containing scope node.
             */
            while (!AcpiNsOpensScope (PrefixNode->Type) &&
                    PrefixNode->Type != ACPI_TYPE_ANY)
            {
                PrefixNode = AcpiNsGetParentNode (PrefixNode);
            }
        }
    }

    /* Save type   TBD: may be no longer necessary */

    TypeToCheckFor = Type;

    /*
     * Begin examination of the actual pathname
     */
    if (!Pathname)
    {
        /* A Null NamePath is allowed and refers to the root */

        NumSegments = 0;
        ThisNode = AcpiGbl_RootNode;
        Path = "";

        ACPI_DEBUG_PRINT ((ACPI_DB_NAMES,
            "Null Pathname (Zero segments), Flags=%X\n", Flags));
    }
    else
    {
        /*
         * Name pointer is valid (and must be in internal name format)
         *
         * Check for scope prefixes:
         *
         * As represented in the AML stream, a namepath consists of an
         * optional scope prefix followed by a name segment part.
         *
         * If present, the scope prefix is either a Root Prefix (in
         * which case the name is fully qualified), or one or more
         * Parent Prefixes (in which case the name's scope is relative
         * to the current scope).
         */
        if (*Path == (UINT8) AML_ROOT_PREFIX)
        {
            /* Pathname is fully qualified, start from the root */

            ThisNode = AcpiGbl_RootNode;
            SearchParentFlag = ACPI_NS_NO_UPSEARCH;

            /* Point to name segment part */

            Path++;

            ACPI_DEBUG_PRINT ((ACPI_DB_NAMES,
                "Path is absolute from root [%p]\n", ThisNode));
        }
        else
        {
            /* Pathname is relative to current scope, start there */

            ACPI_DEBUG_PRINT ((ACPI_DB_NAMES,
                "Searching relative to prefix scope [%4.4s] (%p)\n",
                AcpiUtGetNodeName (PrefixNode), PrefixNode));

            /*
             * Handle multiple Parent Prefixes (carat) by just getting
             * the parent node for each prefix instance.
             */
            ThisNode = PrefixNode;
            NumCarats = 0;
            while (*Path == (UINT8) AML_PARENT_PREFIX)
            {
                /* Name is fully qualified, no search rules apply */

                SearchParentFlag = ACPI_NS_NO_UPSEARCH;
                /*
                 * Point past this prefix to the name segment
                 * part or the next Parent Prefix
                 */
                Path++;

                /* Backup to the parent node */

                NumCarats++;
                ThisNode = AcpiNsGetParentNode (ThisNode);
                if (!ThisNode)
                {
                    /* Current scope has no parent scope */

                    ACPI_ERROR ((AE_INFO,
                        "ACPI path has too many parent prefixes (^) - reached beyond root node"));
                    return_ACPI_STATUS (AE_NOT_FOUND);
                }
            }

            if (SearchParentFlag == ACPI_NS_NO_UPSEARCH)
            {
                ACPI_DEBUG_PRINT ((ACPI_DB_NAMES,
                    "Search scope is [%4.4s], path has %d carat(s)\n",
                    AcpiUtGetNodeName (ThisNode), NumCarats));
            }
        }

        /*
         * Determine the number of ACPI name segments in this pathname.
         *
         * The segment part consists of either:
         *  - A Null name segment (0)
         *  - A DualNamePrefix followed by two 4-byte name segments
         *  - A MultiNamePrefix followed by a byte indicating the
         *      number of segments and the segments themselves.
         *  - A single 4-byte name segment
         *
         * Examine the name prefix opcode, if any, to determine the number of
         * segments.
         */
        switch (*Path)
        {
        case 0:
            /*
             * Null name after a root or parent prefixes. We already
             * have the correct target node and there are no name segments.
             */
            NumSegments  = 0;
            Type = ThisNode->Type;

            ACPI_DEBUG_PRINT ((ACPI_DB_NAMES,
                "Prefix-only Pathname (Zero name segments), Flags=%X\n",
                Flags));
            break;

        case AML_DUAL_NAME_PREFIX:

            /* More than one NameSeg, search rules do not apply */

            SearchParentFlag = ACPI_NS_NO_UPSEARCH;

            /* Two segments, point to first name segment */

            NumSegments = 2;
            Path++;

            ACPI_DEBUG_PRINT ((ACPI_DB_NAMES,
                "Dual Pathname (2 segments, Flags=%X)\n", Flags));
            break;

        case AML_MULTI_NAME_PREFIX_OP:

            /* More than one NameSeg, search rules do not apply */

            SearchParentFlag = ACPI_NS_NO_UPSEARCH;

            /* Extract segment count, point to first name segment */

            Path++;
            NumSegments = (UINT32) (UINT8) *Path;
            Path++;

            ACPI_DEBUG_PRINT ((ACPI_DB_NAMES,
                "Multi Pathname (%d Segments, Flags=%X)\n",
                NumSegments, Flags));
            break;

        default:
            /*
             * Not a Null name, no Dual or Multi prefix, hence there is
             * only one name segment and Pathname is already pointing to it.
             */
            NumSegments = 1;

            ACPI_DEBUG_PRINT ((ACPI_DB_NAMES,
                "Simple Pathname (1 segment, Flags=%X)\n", Flags));
            break;
        }

        ACPI_DEBUG_EXEC (AcpiNsPrintPathname (NumSegments, Path));
    }


    /*
     * Search namespace for each segment of the name.  Loop through and
     * verify (or add to the namespace) each name segment.
     *
     * The object type is significant only at the last name
     * segment.  (We don't care about the types along the path, only
     * the type of the final target object.)
     */
    ThisSearchType = ACPI_TYPE_ANY;
    CurrentNode = ThisNode;
    while (NumSegments && CurrentNode)
    {
        NumSegments--;
        if (!NumSegments)
        {
            /*
             * This is the last segment, enable typechecking
             */
            ThisSearchType = Type;

            /*
             * Only allow automatic parent search (search rules) if the caller
             * requested it AND we have a single, non-fully-qualified NameSeg
             */
            if ((SearchParentFlag != ACPI_NS_NO_UPSEARCH) &&
                (Flags & ACPI_NS_SEARCH_PARENT))
            {
                LocalFlags |= ACPI_NS_SEARCH_PARENT;
            }

            /* Set error flag according to caller */

            if (Flags & ACPI_NS_ERROR_IF_FOUND)
            {
                LocalFlags |= ACPI_NS_ERROR_IF_FOUND;
            }
        }

        /* Extract one ACPI name from the front of the pathname */

        ACPI_MOVE_32_TO_32 (&SimpleName, Path);

        /* Try to find the single (4 character) ACPI name */

        Status = AcpiNsSearchAndEnter (SimpleName, WalkState, CurrentNode,
                    InterpreterMode, ThisSearchType, LocalFlags, &ThisNode);
        if (ACPI_FAILURE (Status))
        {
            if (Status == AE_NOT_FOUND)
            {
                /* Name not found in ACPI namespace */

                ACPI_DEBUG_PRINT ((ACPI_DB_NAMES,
                    "Name [%4.4s] not found in scope [%4.4s] %p\n",
                    (char *) &SimpleName, (char *) &CurrentNode->Name,
                    CurrentNode));
            }

            *ReturnNode = ThisNode;
            return_ACPI_STATUS (Status);
        }

        /* More segments to follow? */

        if (NumSegments > 0)
        {
            /*
             * If we have an alias to an object that opens a scope (such as a
             * device or processor), we need to dereference the alias here so that
             * we can access any children of the original node (via the remaining
             * segments).
             */
            if (ThisNode->Type == ACPI_TYPE_LOCAL_ALIAS)
            {
                if (AcpiNsOpensScope (((ACPI_NAMESPACE_NODE *) ThisNode->Object)->Type))
                {
                    ThisNode = (ACPI_NAMESPACE_NODE *) ThisNode->Object;
                }
            }
        }

        /* Special handling for the last segment (NumSegments == 0) */

        else
        {
            /*
             * Sanity typecheck of the target object:
             *
             * If 1) This is the last segment (NumSegments == 0)
             *    2) And we are looking for a specific type
             *       (Not checking for TYPE_ANY)
             *    3) Which is not an alias
             *    4) Which is not a local type (TYPE_SCOPE)
             *    5) And the type of target object is known (not TYPE_ANY)
             *    6) And target object does not match what we are looking for
             *
             * Then we have a type mismatch. Just warn and ignore it.
             */
            if ((TypeToCheckFor != ACPI_TYPE_ANY)                   &&
                (TypeToCheckFor != ACPI_TYPE_LOCAL_ALIAS)           &&
                (TypeToCheckFor != ACPI_TYPE_LOCAL_METHOD_ALIAS)    &&
                (TypeToCheckFor != ACPI_TYPE_LOCAL_SCOPE)           &&
                (ThisNode->Type != ACPI_TYPE_ANY)                   &&
                (ThisNode->Type != TypeToCheckFor))
            {
                /* Complain about a type mismatch */

                ACPI_WARNING ((AE_INFO,
                    "NsLookup: Type mismatch on %4.4s (%s), searching for (%s)",
                    ACPI_CAST_PTR (char, &SimpleName),
                    AcpiUtGetTypeName (ThisNode->Type),
                    AcpiUtGetTypeName (TypeToCheckFor)));
            }

            /*
             * If this is the last name segment and we are not looking for a
             * specific type, but the type of found object is known, use that type
             * to (later) see if it opens a scope.
             */
            if (Type == ACPI_TYPE_ANY)
            {
                Type = ThisNode->Type;
            }
        }

        /* Point to next name segment and make this node current */

        Path += ACPI_NAME_SIZE;
        CurrentNode = ThisNode;
    }

    /*
     * Always check if we need to open a new scope
     */
    if (!(Flags & ACPI_NS_DONT_OPEN_SCOPE) && (WalkState))
    {
        /*
         * If entry is a type which opens a scope, push the new scope on the
         * scope stack.
         */
        if (AcpiNsOpensScope (Type))
        {
            Status = AcpiDsScopeStackPush (ThisNode, Type, WalkState);
            if (ACPI_FAILURE (Status))
            {
                return_ACPI_STATUS (Status);
            }
        }
    }

    *ReturnNode = ThisNode;
    return_ACPI_STATUS (AE_OK);
}