xref: /freebsd-10-stable/sys/contrib/dev/acpica/components/dispatcher/dsmthdat.c

/*******************************************************************************
 *
 * Module Name: dsmthdat - control method arguments and local variables
 *              $Revision: 80 $
 *
 ******************************************************************************/

/******************************************************************************
 *
 * 1. Copyright Notice
 *
 * Some or all of this work - Copyright (c) 1999 - 2004, Intel Corp.
 * All rights reserved.
 *
 * 2. License
 *
 * 2.1. This is your license from Intel Corp. under its intellectual property
 * rights.  You may have additional license terms from the party that provided
 * you this software, covering your right to use that party's intellectual
 * property rights.
 *
 * 2.2. Intel grants, free of charge, to any person ("Licensee") obtaining a
 * copy of the source code appearing in this file ("Covered Code") an
 * irrevocable, perpetual, worldwide license under Intel's copyrights in the
 * base code distributed originally by Intel ("Original Intel Code") to copy,
 * make derivatives, distribute, use and display any portion of the Covered
 * Code in any form, with the right to sublicense such rights; and
 *
 * 2.3. Intel grants Licensee a non-exclusive and non-transferable patent
 * license (with the right to sublicense), under only those claims of Intel
 * patents that are infringed by the Original Intel Code, to make, use, sell,
 * offer to sell, and import the Covered Code and derivative works thereof
 * solely to the minimum extent necessary to exercise the above copyright
 * license, and in no event shall the patent license extend to any additions
 * to or modifications of the Original Intel Code.  No other license or right
 * is granted directly or by implication, estoppel or otherwise;
 *
 * The above copyright and patent license is granted only if the following
 * conditions are met:
 *
 * 3. Conditions
 *
 * 3.1. Redistribution of Source with Rights to Further Distribute Source.
 * Redistribution of source code of any substantial portion of the Covered
 * Code or modification with rights to further distribute source must include
 * the above Copyright Notice, the above License, this list of Conditions,
 * and the following Disclaimer and Export Compliance provision.  In addition,
 * Licensee must cause all Covered Code to which Licensee contributes to
 * contain a file documenting the changes Licensee made to create that Covered
 * Code and the date of any change.  Licensee must include in that file the
 * documentation of any changes made by any predecessor Licensee.  Licensee
 * must include a prominent statement that the modification is derived,
 * directly or indirectly, from Original Intel Code.
 *
 * 3.2. Redistribution of Source with no Rights to Further Distribute Source.
 * Redistribution of source code of any substantial portion of the Covered
 * Code or modification without rights to further distribute source must
 * include the following Disclaimer and Export Compliance provision in the
 * documentation and/or other materials provided with distribution.  In
 * addition, Licensee may not authorize further sublicense of source of any
 * portion of the Covered Code, and must include terms to the effect that the
 * license from Licensee to its licensee is limited to the intellectual
 * property embodied in the software Licensee provides to its licensee, and
 * not to intellectual property embodied in modifications its licensee may
 * make.
 *
 * 3.3. Redistribution of Executable. Redistribution in executable form of any
 * substantial portion of the Covered Code or modification must reproduce the
 * above Copyright Notice, and the following Disclaimer and Export Compliance
 * provision in the documentation and/or other materials provided with the
 * distribution.
 *
 * 3.4. Intel retains all right, title, and interest in and to the Original
 * Intel Code.
 *
 * 3.5. Neither the name Intel nor any other trademark owned or controlled by
 * Intel shall be used in advertising or otherwise to promote the sale, use or
 * other dealings in products derived from or relating to the Covered Code
 * without prior written authorization from Intel.
 *
 * 4. Disclaimer and Export Compliance
 *
 * 4.1. INTEL MAKES NO WARRANTY OF ANY KIND REGARDING ANY SOFTWARE PROVIDED
 * HERE.  ANY SOFTWARE ORIGINATING FROM INTEL OR DERIVED FROM INTEL SOFTWARE
 * IS PROVIDED "AS IS," AND INTEL WILL NOT PROVIDE ANY SUPPORT,  ASSISTANCE,
 * INSTALLATION, TRAINING OR OTHER SERVICES.  INTEL WILL NOT PROVIDE ANY
 * UPDATES, ENHANCEMENTS OR EXTENSIONS.  INTEL SPECIFICALLY DISCLAIMS ANY
 * IMPLIED WARRANTIES OF MERCHANTABILITY, NONINFRINGEMENT AND FITNESS FOR A
 * PARTICULAR PURPOSE.
 *
 * 4.2. IN NO EVENT SHALL INTEL HAVE ANY LIABILITY TO LICENSEE, ITS LICENSEES
 * OR ANY OTHER THIRD PARTY, FOR ANY LOST PROFITS, LOST DATA, LOSS OF USE OR
 * COSTS OF PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES, OR FOR ANY INDIRECT,
 * SPECIAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THIS AGREEMENT, UNDER ANY
 * CAUSE OF ACTION OR THEORY OF LIABILITY, AND IRRESPECTIVE OF WHETHER INTEL
 * HAS ADVANCE NOTICE OF THE POSSIBILITY OF SUCH DAMAGES.  THESE LIMITATIONS
 * SHALL APPLY NOTWITHSTANDING THE FAILURE OF THE ESSENTIAL PURPOSE OF ANY
 * LIMITED REMEDY.
 *
 * 4.3. Licensee shall not export, either directly or indirectly, any of this
 * software or system incorporating such software without first obtaining any
 * required license or other approval from the U. S. Department of Commerce or
 * any other agency or department of the United States Government.  In the
 * event Licensee exports any such software from the United States or
 * re-exports any such software from a foreign destination, Licensee shall
 * ensure that the distribution and export/re-export of the software is in
 * compliance with all laws, regulations, orders, or other restrictions of the
 * U.S. Export Administration Regulations. Licensee agrees that neither it nor
 * any of its subsidiaries will export/re-export any technical data, process,
 * software, or service, directly or indirectly, to any country for which the
 * United States government or any agency thereof requires an export license,
 * other governmental approval, or letter of assurance, without first obtaining
 * such license, approval or letter.
 *
 *****************************************************************************/

#define __DSMTHDAT_C__

#include "acpi.h"
#include "acdispat.h"
#include "amlcode.h"
#include "acnamesp.h"
#include "acinterp.h"


#define _COMPONENT          ACPI_DISPATCHER
        ACPI_MODULE_NAME    ("dsmthdat")


/*******************************************************************************
 *
 * FUNCTION:    AcpiDsMethodDataInit
 *
 * PARAMETERS:  WalkState           - Current walk state object
 *
 * RETURN:      Status
 *
 * DESCRIPTION: Initialize the data structures that hold the method's arguments
 *              and locals.  The data struct is an array of NTEs for each.
 *              This allows RefOf and DeRefOf to work properly for these
 *              special data types.
 *
 * NOTES:       WalkState fields are initialized to zero by the
 *              ACPI_MEM_CALLOCATE().
 *
 *              A pseudo-Namespace Node is assigned to each argument and local
 *              so that RefOf() can return a pointer to the Node.
 *
 ******************************************************************************/

void
AcpiDsMethodDataInit (
    ACPI_WALK_STATE         *WalkState)
{
    UINT32                  i;


    ACPI_FUNCTION_TRACE ("DsMethodDataInit");


    /* Init the method arguments */

    for (i = 0; i < ACPI_METHOD_NUM_ARGS; i++)
    {
        ACPI_MOVE_32_TO_32 (&WalkState->Arguments[i].Name,
                            NAMEOF_ARG_NTE);
        WalkState->Arguments[i].Name.Integer |= (i << 24);
        WalkState->Arguments[i].Descriptor    = ACPI_DESC_TYPE_NAMED;
        WalkState->Arguments[i].Type          = ACPI_TYPE_ANY;
        WalkState->Arguments[i].Flags         = ANOBJ_END_OF_PEER_LIST | ANOBJ_METHOD_ARG;
    }

    /* Init the method locals */

    for (i = 0; i < ACPI_METHOD_NUM_LOCALS; i++)
    {
        ACPI_MOVE_32_TO_32 (&WalkState->LocalVariables[i].Name,
                            NAMEOF_LOCAL_NTE);

        WalkState->LocalVariables[i].Name.Integer |= (i << 24);
        WalkState->LocalVariables[i].Descriptor    = ACPI_DESC_TYPE_NAMED;
        WalkState->LocalVariables[i].Type          = ACPI_TYPE_ANY;
        WalkState->LocalVariables[i].Flags         = ANOBJ_END_OF_PEER_LIST | ANOBJ_METHOD_LOCAL;
    }

    return_VOID;
}


/*******************************************************************************
 *
 * FUNCTION:    AcpiDsMethodDataDeleteAll
 *
 * PARAMETERS:  WalkState           - Current walk state object
 *
 * RETURN:      None
 *
 * DESCRIPTION: Delete method locals and arguments.  Arguments are only
 *              deleted if this method was called from another method.
 *
 ******************************************************************************/

void
AcpiDsMethodDataDeleteAll (
    ACPI_WALK_STATE         *WalkState)
{
    UINT32                  Index;


    ACPI_FUNCTION_TRACE ("DsMethodDataDeleteAll");


    /* Detach the locals */

    for (Index = 0; Index < ACPI_METHOD_NUM_LOCALS; Index++)
    {
        if (WalkState->LocalVariables[Index].Object)
        {
            ACPI_DEBUG_PRINT ((ACPI_DB_EXEC, "Deleting Local%d=%p\n",
                    Index, WalkState->LocalVariables[Index].Object));

            /* Detach object (if present) and remove a reference */

            AcpiNsDetachObject (&WalkState->LocalVariables[Index]);
        }
    }

    /* Detach the arguments */

    for (Index = 0; Index < ACPI_METHOD_NUM_ARGS; Index++)
    {
        if (WalkState->Arguments[Index].Object)
        {
            ACPI_DEBUG_PRINT ((ACPI_DB_EXEC, "Deleting Arg%d=%p\n",
                    Index, WalkState->Arguments[Index].Object));

            /* Detach object (if present) and remove a reference */

            AcpiNsDetachObject (&WalkState->Arguments[Index]);
        }
    }

    return_VOID;
}


/*******************************************************************************
 *
 * FUNCTION:    AcpiDsMethodDataInitArgs
 *
 * PARAMETERS:  *Params         - Pointer to a parameter list for the method
 *              MaxParamCount   - The arg count for this method
 *              WalkState       - Current walk state object
 *
 * RETURN:      Status
 *
 * DESCRIPTION: Initialize arguments for a method.  The parameter list is a list
 *              of ACPI operand objects, either null terminated or whose length
 *              is defined by MaxParamCount.
 *
 ******************************************************************************/

ACPI_STATUS
AcpiDsMethodDataInitArgs (
    ACPI_OPERAND_OBJECT     **Params,
    UINT32                  MaxParamCount,
    ACPI_WALK_STATE         *WalkState)
{
    ACPI_STATUS             Status;
    UINT32                  Index = 0;


    ACPI_FUNCTION_TRACE_PTR ("DsMethodDataInitArgs", Params);


    if (!Params)
    {
        ACPI_DEBUG_PRINT ((ACPI_DB_EXEC, "No param list passed to method\n"));
        return_ACPI_STATUS (AE_OK);
    }

    /* Copy passed parameters into the new method stack frame  */

    while ((Index < ACPI_METHOD_NUM_ARGS) && (Index < MaxParamCount) && Params[Index])
    {
        /*
         * A valid parameter.
         * Store the argument in the method/walk descriptor.
         * Do not copy the arg in order to implement call by reference
         */
        Status = AcpiDsMethodDataSetValue (AML_ARG_OP, Index, Params[Index], WalkState);
        if (ACPI_FAILURE (Status))
        {
            return_ACPI_STATUS (Status);
        }

        Index++;
    }

    ACPI_DEBUG_PRINT ((ACPI_DB_EXEC, "%d args passed to method\n", Index));
    return_ACPI_STATUS (AE_OK);
}


/*******************************************************************************
 *
 * FUNCTION:    AcpiDsMethodDataGetNode
 *
 * PARAMETERS:  Opcode              - Either AML_LOCAL_OP or AML_ARG_OP
 *              Index               - Which localVar or argument whose type
 *                                      to get
 *              WalkState           - Current walk state object
 *
 * RETURN:      Get the Node associated with a local or arg.
 *
 ******************************************************************************/

ACPI_STATUS
AcpiDsMethodDataGetNode (
    UINT16                  Opcode,
    UINT32                  Index,
    ACPI_WALK_STATE         *WalkState,
    ACPI_NAMESPACE_NODE     **Node)
{
    ACPI_FUNCTION_TRACE ("DsMethodDataGetNode");


    /*
     * Method Locals and Arguments are supported
     */
    switch (Opcode)
    {
    case AML_LOCAL_OP:

        if (Index > ACPI_METHOD_MAX_LOCAL)
        {
            ACPI_DEBUG_PRINT ((ACPI_DB_ERROR, "Local index %d is invalid (max %d)\n",
                Index, ACPI_METHOD_MAX_LOCAL));
            return_ACPI_STATUS (AE_AML_INVALID_INDEX);
        }

        /* Return a pointer to the pseudo-node */

        *Node = &WalkState->LocalVariables[Index];
        break;

    case AML_ARG_OP:

        if (Index > ACPI_METHOD_MAX_ARG)
        {
            ACPI_DEBUG_PRINT ((ACPI_DB_ERROR, "Arg index %d is invalid (max %d)\n",
                Index, ACPI_METHOD_MAX_ARG));
            return_ACPI_STATUS (AE_AML_INVALID_INDEX);
        }

        /* Return a pointer to the pseudo-node */

        *Node = &WalkState->Arguments[Index];
        break;

    default:
        ACPI_DEBUG_PRINT ((ACPI_DB_ERROR, "Opcode %d is invalid\n", Opcode));
        return_ACPI_STATUS (AE_AML_BAD_OPCODE);
    }

    return_ACPI_STATUS (AE_OK);
}


/*******************************************************************************
 *
 * FUNCTION:    AcpiDsMethodDataSetValue
 *
 * PARAMETERS:  Opcode              - Either AML_LOCAL_OP or AML_ARG_OP
 *              Index               - Which localVar or argument to get
 *              Object              - Object to be inserted into the stack entry
 *              WalkState           - Current walk state object
 *
 * RETURN:      Status
 *
 * DESCRIPTION: Insert an object onto the method stack at entry Opcode:Index.
 *              Note: There is no "implicit conversion" for locals.
 *
 ******************************************************************************/

ACPI_STATUS
AcpiDsMethodDataSetValue (
    UINT16                  Opcode,
    UINT32                  Index,
    ACPI_OPERAND_OBJECT     *Object,
    ACPI_WALK_STATE         *WalkState)
{
    ACPI_STATUS             Status;
    ACPI_NAMESPACE_NODE     *Node;


    ACPI_FUNCTION_TRACE ("DsMethodDataSetValue");


    ACPI_DEBUG_PRINT ((ACPI_DB_EXEC,
        "NewObj %p Opcode %X, Refs=%d [%s]\n", Object,
        Opcode, Object->Common.ReferenceCount,
        AcpiUtGetTypeName (Object->Common.Type)));

    /* Get the namespace node for the arg/local */

    Status = AcpiDsMethodDataGetNode (Opcode, Index, WalkState, &Node);
    if (ACPI_FAILURE (Status))
    {
        return_ACPI_STATUS (Status);
    }

    /*
     * Increment ref count so object can't be deleted while installed.
     * NOTE: We do not copy the object in order to preserve the call by
     * reference semantics of ACPI Control Method invocation.
     * (See ACPI Specification 2.0C)
     */
    AcpiUtAddReference (Object);

    /* Install the object */

    Node->Object = Object;
    return_ACPI_STATUS (Status);
}


/*******************************************************************************
 *
 * FUNCTION:    AcpiDsMethodDataGetType
 *
 * PARAMETERS:  Opcode              - Either AML_LOCAL_OP or AML_ARG_OP
 *              Index               - Which localVar or argument whose type
 *                                      to get
 *              WalkState           - Current walk state object
 *
 * RETURN:      Data type of current value of the selected Arg or Local
 *
 ******************************************************************************/

ACPI_OBJECT_TYPE
AcpiDsMethodDataGetType (
    UINT16                  Opcode,
    UINT32                  Index,
    ACPI_WALK_STATE         *WalkState)
{
    ACPI_STATUS             Status;
    ACPI_NAMESPACE_NODE     *Node;
    ACPI_OPERAND_OBJECT     *Object;


    ACPI_FUNCTION_TRACE ("DsMethodDataGetType");


    /* Get the namespace node for the arg/local */

    Status = AcpiDsMethodDataGetNode (Opcode, Index, WalkState, &Node);
    if (ACPI_FAILURE (Status))
    {
        return_VALUE ((ACPI_TYPE_NOT_FOUND));
    }

    /* Get the object */

    Object = AcpiNsGetAttachedObject (Node);
    if (!Object)
    {
        /* Uninitialized local/arg, return TYPE_ANY */

        return_VALUE (ACPI_TYPE_ANY);
    }

    /* Get the object type */

    return_VALUE (ACPI_GET_OBJECT_TYPE (Object));
}


/*******************************************************************************
 *
 * FUNCTION:    AcpiDsMethodDataGetValue
 *
 * PARAMETERS:  Opcode              - Either AML_LOCAL_OP or AML_ARG_OP
 *              Index               - Which localVar or argument to get
 *              WalkState           - Current walk state object
 *              *DestDesc           - Ptr to Descriptor into which selected Arg
 *                                    or Local value should be copied
 *
 * RETURN:      Status
 *
 * DESCRIPTION: Retrieve value of selected Arg or Local from the method frame
 *              at the current top of the method stack.
 *              Used only in AcpiExResolveToValue().
 *
 ******************************************************************************/

ACPI_STATUS
AcpiDsMethodDataGetValue (
    UINT16                  Opcode,
    UINT32                  Index,
    ACPI_WALK_STATE         *WalkState,
    ACPI_OPERAND_OBJECT     **DestDesc)
{
    ACPI_STATUS             Status;
    ACPI_NAMESPACE_NODE     *Node;
    ACPI_OPERAND_OBJECT     *Object;


    ACPI_FUNCTION_TRACE ("DsMethodDataGetValue");


    /* Validate the object descriptor */

    if (!DestDesc)
    {
        ACPI_DEBUG_PRINT ((ACPI_DB_ERROR, "Null object descriptor pointer\n"));
        return_ACPI_STATUS (AE_BAD_PARAMETER);
    }

    /* Get the namespace node for the arg/local */

    Status = AcpiDsMethodDataGetNode (Opcode, Index, WalkState, &Node);
    if (ACPI_FAILURE (Status))
    {
        return_ACPI_STATUS (Status);
    }

    /* Get the object from the node */

    Object = Node->Object;

    /* Examine the returned object, it must be valid. */

    if (!Object)
    {
        /*
         * Index points to uninitialized object.
         * This means that either 1) The expected argument was
         * not passed to the method, or 2) A local variable
         * was referenced by the method (via the ASL)
         * before it was initialized.  Either case is an error.
         */

        /* If slack enabled, init the LocalX/ArgX to an Integer of value zero */

        if (AcpiGbl_EnableInterpreterSlack)
        {
            Object = AcpiUtCreateInternalObject (ACPI_TYPE_INTEGER);
            if (!Object)
            {
                return_ACPI_STATUS (AE_NO_MEMORY);
            }

            Object->Integer.Value = 0;
            Node->Object = Object;
        }

        /* Otherwise, return the error */

        else switch (Opcode)
        {
        case AML_ARG_OP:

            ACPI_DEBUG_PRINT ((ACPI_DB_ERROR, "Uninitialized Arg[%d] at node %p\n",
                Index, Node));

            return_ACPI_STATUS (AE_AML_UNINITIALIZED_ARG);

        case AML_LOCAL_OP:

            ACPI_DEBUG_PRINT ((ACPI_DB_ERROR, "Uninitialized Local[%d] at node %p\n",
                Index, Node));

            return_ACPI_STATUS (AE_AML_UNINITIALIZED_LOCAL);

        default:
            ACPI_REPORT_ERROR (("Not Arg/Local opcode: %X\n", Opcode));
            return_ACPI_STATUS (AE_AML_INTERNAL);
        }
    }

    /*
     * The Index points to an initialized and valid object.
     * Return an additional reference to the object
     */
    *DestDesc = Object;
    AcpiUtAddReference (Object);

    return_ACPI_STATUS (AE_OK);
}


/*******************************************************************************
 *
 * FUNCTION:    AcpiDsMethodDataDeleteValue
 *
 * PARAMETERS:  Opcode              - Either AML_LOCAL_OP or AML_ARG_OP
 *              Index               - Which localVar or argument to delete
 *              WalkState           - Current walk state object
 *
 * RETURN:      None
 *
 * DESCRIPTION: Delete the entry at Opcode:Index on the method stack.  Inserts
 *              a null into the stack slot after the object is deleted.
 *
 ******************************************************************************/

void
AcpiDsMethodDataDeleteValue (
    UINT16                  Opcode,
    UINT32                  Index,
    ACPI_WALK_STATE         *WalkState)
{
    ACPI_STATUS             Status;
    ACPI_NAMESPACE_NODE     *Node;
    ACPI_OPERAND_OBJECT     *Object;


    ACPI_FUNCTION_TRACE ("DsMethodDataDeleteValue");


    /* Get the namespace node for the arg/local */

    Status = AcpiDsMethodDataGetNode (Opcode, Index, WalkState, &Node);
    if (ACPI_FAILURE (Status))
    {
        return_VOID;
    }

    /* Get the associated object */

    Object = AcpiNsGetAttachedObject (Node);

    /*
     * Undefine the Arg or Local by setting its descriptor
     * pointer to NULL. Locals/Args can contain both
     * ACPI_OPERAND_OBJECTS and ACPI_NAMESPACE_NODEs
     */
    Node->Object = NULL;

    if ((Object) &&
        (ACPI_GET_DESCRIPTOR_TYPE (Object) == ACPI_DESC_TYPE_OPERAND))
    {
        /*
         * There is a valid object.
         * Decrement the reference count by one to balance the
         * increment when the object was stored.
         */
        AcpiUtRemoveReference (Object);
    }

    return_VOID;
}


/*******************************************************************************
 *
 * FUNCTION:    AcpiDsStoreObjectToLocal
 *
 * PARAMETERS:  Opcode              - Either AML_LOCAL_OP or AML_ARG_OP
 *              Index               - Which localVar or argument to set
 *              ObjDesc             - Value to be stored
 *              WalkState           - Current walk state
 *
 * RETURN:      Status
 *
 * DESCRIPTION: Store a value in an Arg or Local.  The ObjDesc is installed
 *              as the new value for the Arg or Local and the reference count
 *              for ObjDesc is incremented.
 *
 ******************************************************************************/

ACPI_STATUS
AcpiDsStoreObjectToLocal (
    UINT16                  Opcode,
    UINT32                  Index,
    ACPI_OPERAND_OBJECT     *ObjDesc,
    ACPI_WALK_STATE         *WalkState)
{
    ACPI_STATUS             Status;
    ACPI_NAMESPACE_NODE     *Node;
    ACPI_OPERAND_OBJECT     *CurrentObjDesc;
    ACPI_OPERAND_OBJECT     *NewObjDesc;


    ACPI_FUNCTION_TRACE ("DsStoreObjectToLocal");
    ACPI_DEBUG_PRINT ((ACPI_DB_EXEC, "Opcode=%X Index=%d Obj=%p\n",
        Opcode, Index, ObjDesc));

    /* Parameter validation */

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

    /* Get the namespace node for the arg/local */

    Status = AcpiDsMethodDataGetNode (Opcode, Index, WalkState, &Node);
    if (ACPI_FAILURE (Status))
    {
        return_ACPI_STATUS (Status);
    }

    CurrentObjDesc = AcpiNsGetAttachedObject (Node);
    if (CurrentObjDesc == ObjDesc)
    {
        ACPI_DEBUG_PRINT ((ACPI_DB_EXEC, "Obj=%p already installed!\n",
            ObjDesc));
        return_ACPI_STATUS (Status);
    }

    /*
     * If the reference count on the object is more than one, we must
     * take a copy of the object before we store.  A reference count
     * of exactly 1 means that the object was just created during the
     * evaluation of an expression, and we can safely use it since it
     * is not used anywhere else.
     */
    NewObjDesc = ObjDesc;
    if (ObjDesc->Common.ReferenceCount > 1)
    {
        Status = AcpiUtCopyIobjectToIobject (ObjDesc, &NewObjDesc, WalkState);
        if (ACPI_FAILURE (Status))
        {
            return_ACPI_STATUS (Status);
        }
    }

    /*
     * If there is an object already in this slot, we either
     * have to delete it, or if this is an argument and there
     * is an object reference stored there, we have to do
     * an indirect store!
     */
    if (CurrentObjDesc)
    {
        /*
         * Check for an indirect store if an argument
         * contains an object reference (stored as an Node).
         * We don't allow this automatic dereferencing for
         * locals, since a store to a local should overwrite
         * anything there, including an object reference.
         *
         * If both Arg0 and Local0 contain RefOf (Local4):
         *
         * Store (1, Arg0)             - Causes indirect store to local4
         * Store (1, Local0)           - Stores 1 in local0, overwriting
         *                                  the reference to local4
         * Store (1, DeRefof (Local0)) - Causes indirect store to local4
         *
         * Weird, but true.
         */
        if (Opcode == AML_ARG_OP)
        {
            /*
             * Make sure that the object is the correct type.  This may be overkill, but
             * it is here because references were NS nodes in the past.  Now they are
             * operand objects of type Reference.
             */
            if (ACPI_GET_DESCRIPTOR_TYPE (CurrentObjDesc) != ACPI_DESC_TYPE_OPERAND)
            {
                ACPI_REPORT_ERROR (("Invalid descriptor type while storing to method arg: [%s]\n",
                        AcpiUtGetDescriptorName (CurrentObjDesc)));
                return_ACPI_STATUS (AE_AML_INTERNAL);
            }

            /*
             * If we have a valid reference object that came from RefOf(), do the
             * indirect store
             */
            if ((CurrentObjDesc->Common.Type == ACPI_TYPE_LOCAL_REFERENCE) &&
                (CurrentObjDesc->Reference.Opcode == AML_REF_OF_OP))
            {
                ACPI_DEBUG_PRINT ((ACPI_DB_EXEC,
                        "Arg (%p) is an ObjRef(Node), storing in node %p\n",
                        NewObjDesc, CurrentObjDesc));

                /*
                 * Store this object to the Node (perform the indirect store)
                 * NOTE: No implicit conversion is performed, as per the ACPI
                 * specification rules on storing to Locals/Args.
                 */
                Status = AcpiExStoreObjectToNode (NewObjDesc,
                            CurrentObjDesc->Reference.Object, WalkState,
                            ACPI_NO_IMPLICIT_CONVERSION);

                /* Remove local reference if we copied the object above */

                if (NewObjDesc != ObjDesc)
                {
                    AcpiUtRemoveReference (NewObjDesc);
                }
                return_ACPI_STATUS (Status);
            }
        }

        /*
         * Delete the existing object
         * before storing the new one
         */
        AcpiDsMethodDataDeleteValue (Opcode, Index, WalkState);
    }

    /*
     * Install the Obj descriptor (*NewObjDesc) into
     * the descriptor for the Arg or Local.
     * (increments the object reference count by one)
     */
    Status = AcpiDsMethodDataSetValue (Opcode, Index, NewObjDesc, WalkState);

    /* Remove local reference if we copied the object above */

    if (NewObjDesc != ObjDesc)
    {
        AcpiUtRemoveReference (NewObjDesc);
    }

    return_ACPI_STATUS (Status);
}