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How File System Filter Drivers Are Different from Device Drivers 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. ![]() However, file system filter drivers can also receive-and define-file system control codes (FSCTLs). Like device drivers, file system filter drivers can receive Introduction to I/O Control Codes (IOCTLs). Like device drivers, file system filter drivers can also create their own IRPs and send them to lower-level drivers.īoth kinds of drivers can register for notification (by using callback functions) of various system events. 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.īecause 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 have DriverEntry, dispatch, and I/O completion routines. FILE DRIVER FILTER OPEN FILE WINDOWSThe following subsections describe some of the similarities between file system filter drivers and device drivers in the Microsoft Windows operating system. How File System Filter Drivers Are Similar to Device Drivers In addition, file system filter drivers must support file system-specific features such as caching, locking, sparse files, disk quotas, compression, security, recoverability, reparse points and volume mount points.įor more details on the similarities and differences between file system filter drivers and device drivers, see the following: These operations include creating, opening, closing, and enumerating files and directories getting and setting file, directory, and volume information and reading and writing file data. In contrast, a file system filter driver works in conjunction with one or more file systems to manage file I/O operations. For example, a DVD storage driver controls a DVD drive. FILE DRIVER FILTER OPEN FILE SOFTWARETypical applications for file system filter drivers include antivirus utilities, encryption programs, and hierarchical storage management systemsįile System Filter Drivers Are Not Device DriversĪ device driver is a software component that controls a particular hardware I/O device. Depending on the nature of the driver, the filter can mean log, observe, modify, or even prevent. A file system filter driver is a kernel-mode component that runs as part of the Windows executive.Ī file system filter driver can filter I/O operations for one or more file systems or file system volumes. ![]() For example, an upper-level device filter driver for a keyboard could enforce additional security checks.Īn upper-level class filter driver adds value for all devices of a particular class.Ī file system filter driver is an optional driver that adds value to or modifies the behavior of a file system. There can be any number of upper-level filter drivers for a device.Īn upper-level device filter driver adds value for a particular device. Such drivers are usually provided by IHVs and are optional. Upper-level filter drivers typically provide added-value features for a device (see the Possible Driver Layers figure). For example, a lower-level class filter driver for mouse devices could provide acceleration, performing a nonlinear conversion of mouse movement data. Typically, such filters redefine hardware behavior to match expected specifications.Ī lower-level class filter driver monitors and/or modifies I/O requests for a class of devices. There can be any number of lower-level filter drivers for a device.Ī lower-level device filter driver monitors and/or modifies I/O requests to a particular device. They are typically supplied by IHVs and are optional. ![]() Lower-level filter drivers typically modify the behavior of device hardware (see the Possible Driver Layers figure). ![]()
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