NT Device Names

A named device object has a name of the form \Device\DeviceName. This is known as the NT device name of the device object.

Device Names for WDM Drivers

WDM drivers do not name their device objects directly. Instead, the system imposes a uniform naming scheme that ensures that device names do not conflict between drivers. The naming scheme for WDM drivers is as follows.

  • The PDO for a device is named. The bus driver requests named PDOs for the devices it enumerates. The bus driver specifies the FILE_AUTOGENERATED_DEVICE_NAME device characteristic when it creates the device object. For more information, see Specifying Device Characteristics. The system then automatically generates the device name.

  • FDOs and filter DOs are not named. Function and filter drivers do not request a name when creating the device object.

Any I/O request to a named device object automatically goes to the top object in that device object's stack. Thus, only the PDO is required to be named. User-mode applications do not refer to WDM device objects by name; instead, applications access the device object through its device interface. For more information, see Device Interface Classes.

Driver writers must not name more than one object in a device stack. The operating system checks security settings based on the named object. If two different objects are named and have different security descriptors, the I/O requests that are sent to the object with the weaker security descriptor can reach the device object with the stronger security descriptor.

Device Names for non-WDM Drivers

A non-WDM driver must explicitly specify a name for any named device objects. The driver must create at least one named device object in the \Device object directory to receive I/O requests. The driver specifies the device name as the DeviceName parameter to IoCreateDeviceSecure when creating the device object.

 

 

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