How File System Filter Drivers Are Similar to Device Drivers

File system filter drivers and device drivers in the Microsoft Windows operating system are similar in the following ways:

• Similar Structure

  Like device drivers, file system filter drivers have DriverEntry, dispatch, and I/O completion routines. They call many of the same kernel-mode routines that device drivers call, and they filter I/O requests for devices (that is, file system volumes) with which they are associated.

• Similar Functionality

  • Because file system filter drivers and device drivers are part of the I/O system, they both receive I/O request packets (IRPs) and act on them.

  • Like device drivers, file system filter drivers can also create their own IRPs and send them to lower-level drivers.

  • Both kinds of drivers can register for notification (by using callback functions) of various system events.

• Other Similarities

  • Like device drivers, file system filter drivers can receive I/O Control Codes (IOCTLs). Note that file system filter drivers can also receive and define file system control codes (FSCTLs).

  • Like device drivers, file system filter drivers can be configured to be loaded at system startup time or to be loaded later, after the system startup process is complete.