Initializing a File System Filter Driver
Note
For optimal reliability and performance, use file system minifilter drivers with Filter Manager support instead of legacy file system filter drivers. To port your legacy driver to a minifilter driver, see Guidelines for Porting Legacy Filter Drivers.
The DriverEntry routine for initializing a legacy file system filter driver is similar to the DriverEntry routine for initializing a device driver. After a driver is loaded, the same component that loaded the driver also initializes the driver by calling the driver's DriverEntry routine. For file system filter drivers, the component that loads the driver is either the I/O Manager (for filters whose start type is SERVICE_BOOT_START) or the Service Control Manager (for other start types).
The DriverEntry routine runs in a system thread context at IRQL = PASSIVE_LEVEL. This routine can be pageable and should be in an INIT segment so that it will be discarded. For more information about how to make your driver code pageable, see the Remarks section of MmLockPagableCodeSection.
The DriverEntry routine is defined as follows:
NTSTATUS
(*PDRIVER_INITIALIZE) (
IN PDRIVER_OBJECT DriverObject,
IN PUNICODE_STRING RegistryPath
);
This routine has two input parameters. The first, DriverObject, is the driver object that was created when the file system filter driver was loaded. The second, RegistryPath, is a pointer to a counted Unicode string that contains a path to the driver's registry key.
The DriverEntry routine for a file system filter driver performs the following steps:
Creating the Control Device Object
Registering IRP Dispatch Routines
Registering Fast I/O Dispatch Routines
Registering FsFilter Callback Routines
Performing Any Other Needed Initialization
[Optional] Registering Callback Routines