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Using the Registry in UMDF 1.x Drivers

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Warning

UMDF 2 is the latest version of UMDF and supersedes UMDF 1. All new UMDF drivers should be written using UMDF 2. No new features are being added to UMDF 1 and there is limited support for UMDF 1 on newer versions of Windows 10. Universal Windows drivers must use UMDF 2.

The archived UMDF 1 samples can be found in the Windows 11, version 22H2 - May 2022 Driver Samples Update.

For more info, see Getting Started with UMDF.

UMDF-based drivers can read and write values in the registry by using interfaces of the property store object.

UMDF-based drivers can access four types of registry keys. Drivers can create, read, and write subkeys and values under these keys. The following types of registry keys are available to UMDF-based drivers:

  • Hardware keys

    The PnP manager creates a hardware key, or device key, for each device, in which it stores the device's unique identification information.

    Your driver can retrieve and modify some of the property values under the hardware key. The location of the stored values depends on the method that you use to access them.

    Property values that were created using PropertyStore methods are stored in the \Device Parameters subkey, under the hardware key. To access these properties, your driver calls one of the following methods to obtain a property store interface.

    IWDFDevice::RetrieveDevicePropertyStore
    Obtains a pointer to an IWDFNamedPropertyStore interface.

    IWDFDeviceInitialize::RetrieveDevicePropertyStore
    Obtains a pointer to an IWDFNamedPropertyStore interface.

    IWDFPropertyStoreFactory::RetrieveDevicePropertyStore
    Obtains a pointer to an IWDFNamedPropertyStore2 interface. You can use the SubkeyPath parameter to specify values under a driver-created subkey, such as \Device Parameters\DriverServiceName\subkey.

    Drivers have read-only access to values within the \Device Parameters subkey, and cannot access \Device Parameters\WDF or \Device Parameters\WUDF.

    Property values that were created using the Unified Device Property model are stored in the \Properties subkey, under the hardware key.

    To access these properties, your driver calls IWDFUnifiedPropertyStoreFactory::RetrieveUnifiedDevicePropertyStore to obtain a property store interface. Then the driver can use the IWDFUnifiedPropertyStore interface to modify and retrieve current settings of device properties.

  • Software keys

    A driver's software key is also called its driver key because the registry contains a software key for each driver. The registry contains a list of all of the device classes, and each driver's software key resides under its device class entry. The system stores information about each driver under its software key.

    Your driver can call IWDFPropertyStoreFactory::RetrieveDevicePropertyStore to obtain read or write access to values under its software key. The driver can read and write driver-specific information that is not associated with specific devices.

  • Device interface keys

    The registry contains keys for all of the device interface classes that drivers have created. Under each of these keys is an entry for each instance of the device interface class that a driver has registered.

    If your driver has registered an instance of a device interface class, it can read and write values under the registry's entry for that instance by calling IWDFPropertyStoreFactory::RetrieveDevicePropertyStore. The driver can read and write instance-specific information about the device interface.

  • The DEVICEMAP key

    The registry contains a HKEY_LOCAL_MACHINE\HARDWARE\DEVICEMAP key that some drivers for older technologies, such as serial and parallel ports, use. If your driver supports a technology that uses the DEVICEMAP key, the driver can access subkeys and values under the key by calling IWDFPropertyStoreFactory::RetrieveDevicePropertyStore.

After a driver has called one of the RetrieveDevicePropertyStore methods to open a registry subkey, the driver can use methods exposed by IWDFNamedPropertyStore, IWDFNamedPropertyStore2, or IWDFUnifiedPropertyStore to create, read, and write values under a subkey. The IWDFNamedPropertyStore2 interface also enables drivers to delete values.

For more information about registry keys for drivers, see Overview of Registry Trees and Keys.