WdfFdoInitOpenRegistryKey function (wdffdo.h)

Article
04/18/2022

[Applies to KMDF and UMDF]

The WdfFdoInitOpenRegistryKey method opens a device's hardware key or a driver's software key in the registry and creates a framework registry-key object that represents the registry key.

Syntax

NTSTATUS WdfFdoInitOpenRegistryKey(
  [in]           PWDFDEVICE_INIT        DeviceInit,
  [in]           ULONG                  DeviceInstanceKeyType,
  [in]           ACCESS_MASK            DesiredAccess,
  [in, optional] PWDF_OBJECT_ATTRIBUTES KeyAttributes,
  [out]          WDFKEY                 *Key
);

Parameters

[in] DeviceInit

A pointer to a WDFDEVICE_INIT structure that the driver obtained from its EvtDriverDeviceAdd callback function.

[in] DeviceInstanceKeyType

Specifies which key or subkey to open.

Note

UMDF does not support creating subkeys.

This is a bitwise OR of the following flags (which are defined in Wdm.h).

DeviceInstanceKeyType flag	Meaning	Framework
PLUGPLAY_REGKEY_DEVICE	Opens the device's hardware key.	KMDF/UMDF
PLUGPLAY_REGKEY_DRIVER	Opens the driver's software key. A UMDF driver that sets this flag must also set DesiredAccess to KEY_READ. Otherwise this method returns STATUS_ACCESS_DENIED.	KMDF/UMDF
PLUGPLAY_REGKEY_CURRENT_HWPROFILE	A KMDF driver uses this flag to open the copy of the hardware or software key that is in the current hardware profile.	KMDF
PLUGPLAY_REGKEY_DRIVER \| WDF_REGKEY_DRIVER_SUBKEY	A UMDF driver uses these flags together to open the ServiceName subkey of the driver's software key for read/write access.	UMDF
PLUGPLAY_REGKEY_DEVICE \| WDF_REGKEY_DEVICE_SUBKEY	Similarly, a UMDF driver uses these flags to open the ServiceName subkey of the device's hardware key for read/write access.	UMDF

[in] DesiredAccess

An ACCESS_MASK-typed value that specifies access rights that the driver is requesting for the specified registry key.

A KMDF driver typically requests KEY_READ, KEY_WRITE, or KEY_READ | KEY_WRITE.

If you are writing a UMDF driver, use the following table.

DeviceInstanceKeyType	DesiredAccess
PLUGPLAY_REGKEY_DEVICE	KEY_READ
PLUGPLAY_REGKEY_DEVICE \| WDF_REGKEY_DEVICE_SUBKEY	KEY_READ or KEY_READ \| KEY_SET_VALUE
PLUGPLAY_REGKEY_DRIVER	KEY_READ
PLUGPLAY_REGKEY_DRIVER \| WDF_REGKEY_DRIVER_SUBKEY	KEY_READ or KEY_READ \| KEY_SET_VALUE

As a best practice, ask for only the types of access that your driver needs.

[in, optional] KeyAttributes

A pointer to a WDF_OBJECT_ATTRIBUTES structure that contains driver-supplied attributes for the new registry-key object. This parameter is optional and can be WDF_NO_OBJECT_ATTRIBUTES.

[out] Key

A pointer to a location that receives a handle to the new registry-key object.

Return value

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

Return code	Description
STATUS_INVALID_DEVICE_REQUEST	WdfFdoInitOpenRegistryKey was not called at IRQL = PASSIVE_LEVEL.
STATUS_INVALID_PARAMETER	An invalid parameter was specified, or the driver did not obtain the WDFDEVICE_INIT structure from its EvtDriverDeviceAdd callback function. For UMDF, this return value can indicate insufficient access rights.
STATUS_INSUFFICIENT_RESOURCES	A registry-key object could not be allocated.
STATUS_OBJECT_NAME_NOT_FOUND	The specified registry key does not exist.

For a list of other return values that the WdfFdoInitOpenRegistryKey method might return, see Framework Object Creation Errors.

The method might also return other NTSTATUS values.

Remarks

The driver must call WdfFdoInitOpenRegistryKey before calling WdfDeviceCreate. For more information about calling WdfDeviceCreate, see Creating a Framework Device Object.

For more information about the WdfFdoInitOpenRegistryKey method, see Creating Device Objects in a Function Driver.

or more information about the registry, hardware and software keys, and registry objects, see Using the Registry in Framework-Based Drivers.

Examples

The following code example opens a device's hardware key, with read access.

WDFKEY key;
NTSTATUS status;

status = WdfFdoInitOpenRegistryKey(
                                   DeviceInit,
                                   PLUGPLAY_REGKEY_DEVICE,
                                   GENERIC_READ,
                                   WDF_NO_OBJECT_ATTRIBUTES,
                                   &key
                                   );
if (!NT_SUCCESS(status)) {
    return status;
}

Requirements

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

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