WdfRegistryQueryValue function (wdfregistry.h)

Artikel
04/18/2022

[Applies to KMDF and UMDF]

The WdfRegistryQueryValue method retrieves the data that is currently assigned to a specified registry value.

Syntax

NTSTATUS WdfRegistryQueryValue(
  [in]            WDFKEY           Key,
  [in]            PCUNICODE_STRING ValueName,
  [in]            ULONG            ValueLength,
  [out, optional] PVOID            Value,
  [out, optional] PULONG           ValueLengthQueried,
  [out, optional] PULONG           ValueType
);

Parameters

[in] Key

A handle to a registry-key object that represents an opened registry key.

[in] ValueName

A pointer to a UNICODE_STRING structure that contains a value name.

[in] ValueLength

The length, in bytes, of the buffer that Value points to.

[out, optional] Value

A pointer to a driver-allocated buffer that receives the registry value's data. If this pointer is NULL, WdfRegistryQueryValue retrieves the data length but not the data.

[out, optional] ValueLengthQueried

A pointer to a location that receives the registry value's data length. This pointer is optional and can be NULL.

[out, optional] ValueType

A pointer to a location that receives the registry value's data type. For a list of data type values, see the Type member of KEY_VALUE_BASIC_INFORMATION. This pointer is optional and can be NULL.

Return value

WdfRegistryQueryValue returns STATUS_SUCCESS if the operation succeeds. Otherwise, the method might return one of the following values:

Return code	Description
STATUS_INVALID_DEVICE_REQUEST	WdfRegistryQueryValue was not called at IRQL = PASSIVE_LEVEL.
STATUS_INVALID_PARAMETER	An invalid parameter was specified.
STATUS_ACCESS_DENIED	The driver did not open the registry key with KEY_QUERY_VALUE, KEY_READ, or KEY_ALL_ACCESS access.
STATUS_BUFFER_OVERFLOW	The buffer that the Value parameter points to is too small, and only partial data has been written to the buffer.
STATUS_BUFFER_OVERFLOW	The Value buffer is too small, and no data has been written to the buffer.
STATUS_OBJECT_NAME_NOT_FOUND	The registry value was not available.

This method also might return other NTSTATUS values.

A bug check occurs if the driver supplies an invalid object handle.

Remarks

For more information about registry-key objects, see Using the Registry in Framework-Based Drivers.

Examples

The following code example opens a device's hardware key and retrieves the data that is assigned to the NumberOfToasters value, which is stored under the device's hardware key.

WCHAR  comPort[FM_COM_PORT_STRING_LENGTH];
ULONG  length;
NTSTATUS  status;
ULONG  length, valueType, value;
DECLARE_CONST_UNICODE_STRING(valueName, L"NumberOfToasters");
WDFKEY  hKey;

status = WdfDeviceOpenRegistryKey(
                                  Device,
                                  PLUGPLAY_REGKEY_DEVICE,
                                  KEY_QUERY_VALUE,
                                  NULL, 
                                  &hKey
                                  );
if (!NT_SUCCESS (status)) {
    goto Error;
}
status = WdfRegistryQueryValue(
                               hKey,
                               &valueName,
                               sizeof(ULONG),
                               &value,
                               &length,
                               &valueType
                               );

Requirements

Requirement	Value
Target Platform	Universal
Minimum KMDF version	1.0
Minimum UMDF version	2.0
Header	wdfregistry.h (include Wdf.h)
Library	Wdf01000.sys (KMDF); WUDFx02000.dll (UMDF)
IRQL	PASSIVE_LEVEL
DDI compliance rules	DriverCreate(kmdf), KmdfIrql(kmdf), KmdfIrql2(kmdf), KmdfIrqlExplicit(kmdf)

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