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WdfRegistryQueryValue function (wdfregistry.h)
[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 |
|---|---|
|
WdfRegistryQueryValue was not called at IRQL = PASSIVE_LEVEL. |
|
An invalid parameter was specified. |
|
The driver did not open the registry key with KEY_QUERY_VALUE, KEY_READ, or KEY_ALL_ACCESS access. |
|
The buffer that the Value parameter points to is too small, and only partial data has been written to the buffer. |
|
The Value buffer is too small, and no data has been written to the buffer. |
|
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) |
See also
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