Storage Class Driver's RemoveDevice Routine

When a device is about to be removed, the PnP manager first calls the class driver's DispatchPnP routine with a PnP query-remove request (IRP_MJ_PNP with IRP_MN_QUERY_REMOVE_DEVICE. The storage class driver should fail the query-remove request in any of the following cases:

• The device contains the system paging file or hibernation file.

• The driver is running a long operation which should not be canceled (for example, rewinding or formatting a tape).

• There are outstanding handles to the device (CREATEs).

The storage class driver might also fail a query-remove request if the device is claimed for crash dump, because removing such a device disables crash dump.

If the storage class driver returns STATUS_SUCCESS in response to a query-remove request, the PnP manager then calls the class driver's DispatchPnP routine with a PnP remove request (IRP_MJ_PNP with IRP_MN_REMOVE_DEVICE). The storage class driver's DispatchPnP routine either calls an internal RemoveDevice routine or implements the same functionality inline.

A storage class driver's RemoveDevice routine must do the following:

• Release any outstanding resources, such as memory or events, allocated by the driver.

• Delete symbolic links, if any, created by the driver.

• Delete the device object (FDO).

• Forward the request to the next-lower driver.

If the storage class driver created PDOs at startup (for example, to represent partitions on a partitioned media device), such PDOs have already been removed when the PnP manager sends the remove request to the storage class driver.

Even after a device object has been deleted, if it has a nonzero reference count the device object persists in the system until its reference count reaches zero, then disappears silently. A storage class driver must not attempt to use the device object pointer after the device object has been deleted.

For more information about handling a remove request, see Removing a Device.