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Microsoft Keyboards Driver

Mouse and Keyboard Center helps you personalize and customize how you work on your PC. Tailor your mouse and keyboard to meet your unique needs and work style. Modify your mouse and keyboard settings to make it easier to use the unique features of most PC apps. Effortlessly transition to Mouse and Keyboard Center from existing device management. Open and close via the class driver The Microsoft Win32 subsystem opens all keyboard and mouse devices for its exclusive use. For each device class, the Win32 subsystem treats input from all the devices as if the input came from a single input device. An application cannot request to receive input from only one particular device. Non-HID keyboards and mice can connect over multiple legacy buses but still use the same class driver. This section contains details on the class drivers themselves. The following sections goes into details on the controllers. This topic describes the typical physical configuration of keyboard and mouse devices in Microsoft Windows 2000 and later. The Microsoft Mouse and Keyboard Center is an app that helps you make the most out of your Microsoft keyboard and mouse. Mouse and Keyboard Center helps you personalize and customize how you work on your PC. This latest release supports these new devices: - Microsoft Bluetooth Ergonomic Mouse - Microsoft Designer Compact Keyboard - Microsoft.

  1. Microsoft Keyboards Drivers
  2. Microsoft Keyboards Drivers
  3. Microsoft Keyboard Drivers
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Non-HID keyboards and mice can connect over multiple legacy buses but still use the same class driver. This section contains details on the class drivers themselves. The following sections goes into details on the controllers.

This topic describes the typical physical configuration of keyboard and mouse devices in Microsoft Windows 2000 and later.

The following figures show two common configurations that employ a single keyboard and a single mouse.

The figure on the left shows a keyboard and a mouse connected to a system bus through independent controllers. A typical configuration consists of a PS/2-style keyboard operated through an i8042 controller, and a serial-style mouse operated through a serial port controller.

Microsoft Keyboards Driver

The following additional information is important for keyboard and mice manufactures:

  • Keyboards are opened in exclusive mode by the operating system stack for security reasons
  • Windows supports the simultaneous connection of more than one keyboard and mouse device.
  • Windows does not support independent access by a client to each device.
Keyboards

Class driver features

This topic describes the features of the following Microsoft Windows 2000 and later system class drivers:

  • Kbdclass, the class driver for devices of GUID_CLASS_KEYBOARD device class

  • Mouclass, the class driver for devices of GUID_CLASS_MOUSE device class

Kbdclass implements the Kbdclass service and its executable image is kbdclass.sys.

Mouclass implements the Mouclass service and its executable image is mouclass.sys.

Kbdclass and Mouclass each feature:

  • Generic and hardware-independent operation of the device class.

  • Plug and Play, power management, and Windows Management Instrumentation (WMI).

  • Operation of legacy devices.

  • Simultaneous operation of more than one device.

  • Connection of a class service callback routine that a function driver uses to transfer data from the input data buffer of the device to the data buffer of the class driver.

Configuration of device objects

The following figure shows the configuration of device objects for a Plug and Play PS/2-style keyboard and mouse device. Each class driver creates an upper-level class filter device object (filter DO) that is attached to a function device object (FDO) through an optional upper-level device filter DO. An upper-level device filter driver creates the upper-level device filter DO. I8042prt creates the function DO and attaches it to a physical device object (PDO) created by the root bus driver.

PS/2 Keyboard

The keyboard driver stack consists of the following.

  • Kbdclass, the upper-level keyboard class filter driver
  • One or more optional upper-level keyboard filter driver
  • I8042prt, the function driver

PS/2 Mouse

The mouse driver stack consists of the following.

  • Mouclass, the upper-level mouse class filter driver
  • One or more optional upper-level mouse filter driver
  • I8042prt, the function driver

Kbdclass and Mouclass can support more than one device in two different modes. In the one-to-one mode, each device has an independent device stack. The class driver creates and attaches an independent class DO to each device stack. Each device stack has its own control state and input buffer. The Microsoft Win32 subsystem accesses input from each device through a unique file object.

In the grandmaster mode, the class driver operates all the devices in the following way:

  • The class driver creates both a grandmaster class DO that represents all of the devices and a subordinate class DO for each device.

    The class driver attaches a subordinate class DO to each device stack. Below the subordinate class DO, the device stack is same as that created in the one-to-one mode.

  • The grandmaster class DO controls the operation of all the subordinate DOs.

  • The Win32 subsystem accesses all device input through the file object that represents the grandmaster class device.

  • All device input is buffered in the grandmaster's data queue.

  • The grandmaster maintains a single global device state.

Kbdclass and Mouclass operate in the one-to-one mode if their registry entry value ConnectMultiplePorts is set to 0x00 (under the key HKLMServicesCurrentControlSet<class service>Parameters, where class service is Kbdclass or Mouclass). Otherwise Kbdclass and Mouclass operate in grandmaster mode.

Open and close via the class driver

The Microsoft Win32 subsystem opens all keyboard and mouse devices for its exclusive use. For each device class, the Win32 subsystem treats input from all the devices as if the input came from a single input device. An application cannot request to receive input from only one particular device.

The Win32 subsystem dynamically opens Plug and Play input devices after it receives notification from the Plug and Play manager that a GUID_CLASS_KEYBOARD or GUID_CLASS_MOUSE device interface is enabled. The Win32 subsystem closes Plug and Play devices after it receives notification that an opened interface is disabled. The Win32 subsystem also opens legacy devices by name (for example, 'DeviceKeyboardLegacyClass0'). Note that once the Win32 subsystem successfully opens a legacy device, it cannot determine if the device is later physically removed.

After Kbdclass and Mouclass receive a create request they do the following for Plug and Play and legacy operation:

  • Plug and Play Operation

    If the device is in the Plug and Play started state, the class driver sends the IRP_MJ_CREATE request down the driver stack. Otherwise the class driver completes the request without sending the request down the driver stack. The class driver sets the trusted file that has read access to the device. If there is a grandmaster device, the class driver sends a create request to all the ports that are associated with the subordinate class devices.

  • Legacy Operation

    The class driver sends an internal device control request to the port driver to enable the device.

Connect a service callback to a device

The class drivers must connect their class service to a device before the device can be opened. The class drivers connect their class service after they attach a class DO to a device stack. The function driver uses the class service callback to transfer input data from a device to the class data queue for the device. The function driver's ISR dispatch completion routine for a device calls the class service callback. Kbdclass provides the class service callback KeyboardClassServiceCallback, and Mouclass provides the class service callback MouseClassServiceCallback.

A vendor can modify the operation of a class service callback by installing an upper-level filter driver for a device. The sample keyboard filter driver Kbfiltr defines the KbFilter_ServiceCallback callback, and the sample mouse filter driver Moufiltr defines the MouFilter_ServiceCallback callback. The sample filter service callbacks can be configured to modify the input data that is transferred from the port input buffer for a device to the class data queue. For example, the filter service callback can delete, transform, or insert data.

Microsoft Keyboards Driver

The class and filter service callbacks are connected in the following way:

  • The class driver sends an internal device connect request down the device stack (IOCTL_INTERNAL_KEYBOARD_CONNECT or IOCTL_INTERNAL_MOUSE_CONNECT). The class connect data is specified by a CONNECT_DATA structure that includes a pointer to the class device object, and a pointer to the class service callback.

  • After the filter driver receives the connect request, it saves a copy of the class connect data, and replaces the request's connect data with filter connect data. The filter connect data specifies a pointer to the filter device object and a pointer to the filter driver service callback. The filter driver then sends the filtered connect request to the function driver.

The class and filter service callbacks are called in the following way:

  • The function driver uses the filter connect data to make the initial callback to the filter service callback.

  • After filtering the input data, the filter service callback uses the class connect data that it saved to make a callback to the class service callback.

Query and set a keyboard device

I8042prt supports the following internal device control requests to query information about a keyboard device, and to set parameters on a keyboard device:

For more information about all keyboard device control requests, see Human Interface Devices Reference.

Scan code mapper for keyboards

In Microsoft Windows operating systems, PS/2-compatible scan codes provided by an input device are converted into virtual keys, which are propagated through the system in the form of Windows messages. If a device produces an incorrect scan code for a certain key, the wrong virtual key message will be sent. This can be fixed by writing a filter driver that analyzes the scan codes generated by firmware and modifies the incorrect scan code to one understood by the system. However, this is a tedious process and can sometimes lead to severe problems, if errors exist in the kernel-level filter driver.

Windows 2000 and Windows XP include a new Scan Code Mapper, which provides a method that allows for mapping of scan codes. The scan code mappings for Windows are stored in the following registry key:

Note There is also a Keyboard Layouts key (notice the plural form) under the Control key, but that key should not be modified.

In the Keyboard Layout key, the Scancode Map value must be added. This value is of type REG_BINARY (little Endian format) and has the data format specified in the following table.

Start offset (in bytes)Size (in bytes)Data
04Header: Version Information
44Header: Flags
84Header: Number of Mappings
124Individual Mapping
.........
Last 4 bytes4Null Terminator (0x00000000)

The first and second DWORDS store header information and should be set to all zeroes for the current version of the Scan Code Mapper. The third DWORD entry holds a count of the total number of mappings that follow, including the null terminating mapping. The minimum count would therefore be 1 (no mappings specified). The individual mappings follow the header. Each mapping is one DWORD in length and is divided into two WORD length fields. Each WORD field stores the scan code for a key to be mapped.

Once the map is stored in the registry, the system must be rebooted for the mappings to take effect. Note that if the mapping of a scan code is necessary on a keypress, the step is performed in user mode just before the scan code is converted to a virtual key. Doing this conversion in user mode can present certain limitations, such as mapping not working correctly when running under Terminal Services.

To remove these mappings, remove the Scancode Map registry value and reboot.

Example 1

The following presents an example. To swap the left CTRL key with the CAPS LOCK key, use a registry editor (preferably Regedt32.exe) to modify the Scancode Map key with the following value:

The following table contains these entries broken into DWORD fields and the bytes swapped.

Value: Interpretation

0x00000000: Header: Version. Set to all zeroes.

0x00000000: Header: Flags. Set to all zeroes.

0x00000003: Three entries in the map (including null entry).

0x001D003A: Left CTRL key --> CAPS LOCK (0x1D --> 0x3A).

0x003A001D: CAPS LOCK --> Left CTRL key (0x3A --> 0x1D).

0x00000000: Null terminator.

Example 2

It is also possible to add a key not generally available on a keyboard or to remove a key that is never used. The following example shows the value stored in Scancode Map to remove the right CTRL key and change the functionality of the right ALT key to work as a mute key:

The following table contains these entries broken into DWORD fields and the bytes swapped.

Value: Interpretation

0x00000000: Header: Version. Set to all zeroes.

0x00000000: Header: Flags. Set to all zeroes.

0x00000003: Three entries in the map (including null entry).

0xE01D0000: Remove the right CTRL key (0xE01D --> 0x00).

0xE038E020: Right ALT key --> Mute key (0xE038 --> 0xE020).

0x00000000: Null terminator.

After the necessary data is generated, it can be inserted into the registry in several ways.

  • A .reg file can be generated that can be easily incorporated into the system registry using a registry editor.
  • An .inf file can also be created with an [AddReg] section that contains the registry information to be added.
  • Regedt32.exe can be used to manually add the information to the registry.

The Scan Code Mapper has several advantages and disadvantages.

The advantages include:

  • The Mapper can be used as an easy fix to correct firmware errors.
  • Frequently used keys can be added to the keyboard by modifying the map in registry. Keys that aren't often used (for example, right CTRL key) can be mapped to null (removed) or exchanged for other keys.
  • Key locations can be altered easily. Users can easily customize the location of frequently used keys for their benefit.

The following disadvantages are recognized:

  • Once the map is stored in the registry, a system reboot is required to activate it.
  • The mappings stored in the registry work at system level and apply to all users. These mappings cannot be set to work differently depending on the current user.
  • The current implementation restricts the functionality of the map such that mappings always apply to all keyboards connected to the system. It is not currently possible to create a map on a per-keyboard basis.

Microsoft Keyboards Drivers

Query a mouse device

I8042prt supports the following internal device control request to query information about a mouse device:

For more information about all mouse device control requests, see Human Interface Devices Reference.

Registry settings associated with mouse class driver

The following is a list of registry keys associated with the mouse class driver.

[Key: HKLMSYSTEMCurrentControlSetServicesMouclassParameters]

  • MaximumPortsServiced – Not used on Windows XP and later. Only for Windows NT4.
  • PointerDeviceBaseName – Specifies the base name for the device objects created by the mouse class device driver
  • ConnectMultiplePorts – Determines whether there is one or more than one port device object for each class device object. This entry is used primarily by device drivers.
  • MouseDataQueueSize - Specifies the number of mouse events buffered by the mouse driver. It also is used in calculating the size of the mouse driver's internal buffer in the nonpaged memory pool.

Absolute pointing devices

For devices of type GUID_CLASS_MOUSE, a device's function driver:

  • Handles device-specific input.

  • Creates the MOUSE_INPUT_DATA structures required by MouseClassServiceCallback.

  • Transfers MOUSE_INPUT_DATA structures to the Mouclass data queue by calling MouseClassServiceCallback in its ISR dispatch completion routine.

For an absolute pointing device, the device's function driver must set the LastX, LastY, and Flags members of the MOUSE_INPUT_DATA structures in the following way:

  • In addition to dividing the device input value by the maximum capability of the device, the driver scales the device input value by 0xFFFF:

  • The driver sets the MOUSE_MOVE_ABSOLUTE flag in Flags.

  • If the input should be mapped by Window Manager to an entire virtual desktop, the driver sets the MOUSE_VIRTUAL_DESKTOP flag in Flags. If the MOUSE_VIRTUAL_DESKTOP flag is not set, Window Manager maps the input to only the primary monitor.

KeyboardsMicrosoft keyboard driver for windows 8

The following specifies, by type of device, how these special requirements for an absolute pointing device are implemented:

  • HID devices:

    Mouhid, the Windows function driver for HID mouse devices, implements these special requirements automatically.

  • PS/2-style devices:

    An upper-level filter driver is required. The filter driver supplies an IsrHook callback and a class service callback. I8042prt calls the IsrHook to handle raw device input, and calls the filter class service callback to filter the input. The filter class service callback, in turn, calls MouseClassServiceCallback. The combination of the IsrHook callback and the class service callback handles device-specific input, creates the required MOUSE_INPUT_DATA structures, scales the device input data, and sets the MOUSE_MOVE_ABSOLUTE flag.

  • Plug and Play COM port devices that are enumerated by Serenum:

    A Plug and Play function driver is required. The function driver creates the required MOUSE_INPUT_DATA structures, scales the device input data, and sets the MOUSE_MOVE_ABSOLUTE flag before it calls MouseClassServiceCallback.

  • Non-Plug and Play COM port devices:

    A device-specific function driver is required. The function driver creates the required MOUSE_INPUT_DATA structures, scales the device input data, and sets the MOUSE_MOVE_ABSOLUTE flag before it calls MouseClassServiceCallback.

  • Device on an unsupported bus:

    A device-specific function driver is required. The function driver creates the required MOUSE_INPUT_DATA structures, scales the device input data, and sets the MOUSE_MOVE_ABSOLUTE flag before it calls MouseClassServiceCallback.

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Note

This topic is for developers who are creating drivers for keyboard and mouse HID clients. If you are looking to fix a mouse or keyboard, see:

This topic discusses keyboard and mouse HID client drivers. Keyboards and mice represent the first set of HID clients that were standardized in the HID Usage tables and implemented in Windows operating systems.

Keyboard and mouse HID client drivers are implemented in the form of HID Mapper Drivers. A HID mapper driver is a kernel-mode WDM filter driver that provides a bidirectional interface for I/O requests between a non-HID Class driver and the HID class driver. The mapper driver maps the I/O requests and data protocols of one to the other.

Windows provides system-supplied HID mapper drivers for HID keyboard, and HID mice devices.

Architecture and overview

The following figure illustrates the system-supplied driver stacks for USB keyboard and mouse/touchpad devices.

The figure above includes the following components:

  • KBDHID.sys – HID client mapper driver for keyboards. Converts HID usages into scancodes to interface with the existing keyboard class driver.
  • MOUHID.sys – HID client mapper driver for mice/touchpads. Converts HID usages into mouse commands (X/Y, buttons, wheel) to interface with the existing keyboard class driver.
  • KBDCLASS.sys – The keyboard class driver maintains functionality for all keyboards and keypads on the system in a secure manner.
  • MOUCLASS.sys – The mouse class driver maintains functionality for all mice / touchpads on the system. The driver does support both absolute and relative pointing devices. This is not the driver for touchscreens as that is managed by a different driver in Windows.
  • HIDCLASS.sys - The HID class driver. The HID Class driver is the glue between KBDHID.sys and MOUHID.sys HID clients and various transports (USB, Bluetooth, etc).

The system builds the driver stack as follows:

  • The transport stack creates a physical device object (PDO) for each HID device attached and loads the appropriate HID transport driver which in turn loads the HID Class Driver.
  • The HID class driver creates a PDO for each keyboard or mouse TLC. Complex HID devices (more than 1 TLC) are exposed as multiple PDOs created by HID class driver. For example, a keyboard with an integrated mouse might have one collection for the standard keyboard controls and a different collection for the mouse.
  • The keyboard or mouse hid client mapper drivers are loaded on the appropriate FDO.
  • The HID mapper drivers create FDOs for keyboard and mouse, and load the class drivers.

Important notes:

  • Vendor drivers are not required for keyboards and mice that are compliant with the supported HID Usages and top level collections.
  • Vendors may optionally provide filter drivers in the HID stack to alter/enhance the functionality of these specific TLC.
  • Vendors should create separate TLCs, that are vendor specific, to exchange vendor proprietary data between their hid client and the device. Avoid using filter drivers unless critical.
  • The system opens all keyboard and mouse collections for its exclusive use.
  • The system prevents disable/enabling a keyboard.
  • The system provides support for horizontal/vertical wheels with smooth scrolling capabilities.

Driver Guidance

Microsoft provides the following guidance for IHVs writing drivers:

  1. Driver developers are allowed to add additional drivers in the form of a filter driver or a new HID Client driver. The criteria are described below:

    1. Filters Drivers: Driver developers should ensure that their value-add driver is a filter driver and does not replace (or be used in place of) existing Windows HID drivers in the input stack.

      • Filter drivers are allowed in the following scenarios:
        • As an upper filter to kbdhid/mouhid
        • As an upper filter to kbdclass/mouclass
      • Filter drivers are not recommended as a filter between HIDCLASS and HID Transport minidriver
    2. Function Drivers: Alternatively vendors can create a function driver (instead of a filter driver) but only for vendor specific HID PDOs (with a user mode service if necessary).

      Function drivers are allowed in the following scenarios:

      • Only load on the specific vendor’s hardware
    3. Transport Drivers: Windows team does not recommend creating additional HID Transport minidriver as they are complex drivers to write/maintain. If a partner is creating a new HID Transport minidriver, especially on SoC systems, we recommend a detailed architectural review to understand the reasoning and ensure that the driver is developed correctly.

  2. Driver developers should leverage driver Frameworks (KMDF or UMDF) and not rely on WDM for their filter drivers.

  3. Driver developers should reduce the number of kernel-user transitions between their service and the driver stack.

  4. Driver developers should ensure ability to wake the system via both keyboard and touchpad functionality (adjustable by the end user (device manager) or the PC manufacturer). In addition on SoC systems, these devices must be able to wake themselves from a lower powered state while the system is in a working S0 state.

  5. Driver developers should ensure that their hardware is power managed efficiently.

    • Device can go into its lowest power state when the device is idle.
    • Device is in the lowest power state when the system is in a low power state (for example, standby (S3) or connected standby).

Keyboard layout

A keyboard layout fully describes a keyboard's input characteristics for Microsoft Windows 2000 and later versions. For example, a keyboard layout specifies the language, keyboard type and version, modifiers, scan codes, and so on.

See the following for information about keyboard layouts:

  • Keyboard header file, kdb.h, in the Windows Driver Development Kit (DDK), which documents general information about keyboard layouts.

  • Sample keyboard layouts.

To visualize the layout of a specific keyboard, see Windows Keyboard Layouts.

For additional details around the keyboard layout, visit Control PanelClock, Language, and RegionLanguage.

Supported buttons and wheels on mice

The following table identifies the features supported across different client versions of the Windows operating system.

FeatureWindows XPWindows VistaWindows 7Windows 8 and later
Buttons 1-5Supported (P/2 & HID)Supported (PS/2 & HID)Supported (PS/2 & HID)Supported (PS/2 & HID)
Vertical Scroll WheelSupported (PS/2 & HID)Supported (PS/2 & HID)Supported (PS/2 & HID)Supported (PS/2 & HID)
Horizontal Scroll WheelNot SupportedSupported(HID only)Supported(HID only)Supported(HID only)
Smooth Scroll Wheel Support (Horizontal and Vertical)Not SupportedPartly SupportedSupported (HID only)Supported (HID only)

Activating buttons 4-5 and wheel on PS/2 mice

The method used by Windows to activate the new 4&5-button + wheel mode is an extension of the method used to activate the third button and the wheel in IntelliMouse-compatible mice:

  • First, the mouse is set to the 3-button wheel mode, which is accomplished by setting the report rate consecutively to 200 reports/second, then to 100 reports/second, then to 80 reports/second, and then reading the ID from the mouse. The mouse should report an ID of 3 when this sequence is completed.
  • Next, the mouse is set to the 5-button wheel mode, which is accomplished by setting the report rate consecutively to 200 reports/second, then to 200 reports/second again, then to 80 reports/second, and then reading the ID from the mouse. Once this sequence is completed, a 5-button wheel mouse should report an ID of 4 (whereas an IntelliMouse-compatible 3-button wheel mouse would still report an ID of 3).

Note that this is applicable to PS/2 mice only and is not applicable to HID mice (HID mice must report accurate usages in their report descriptor).

Standard PS/2-compatible mouse data packet format (2 Buttons)

ByteD7D6D5D4D3D2D1D0Comment
1YoverXoverYsignXsignTagMRLX/Y overvlows and signs, buttons
2X7X6X5X4X3X2X1X0X data byte
3Y7Y6Y5Y4Y3Y2Y1Y0Y data bytes

Note

Windows mouse drivers do not check the overflow bits. In case of overflow, the mouse should simply send the maximal signed displacement value.

Standard PS/2-compatible mouse data packet format (3 Buttons + VerticalWheel)

ByteD7D6D5D4D3D2D1D0Comment
100YsignXsign1MRLX/Y signs and R/L/M buttons
2X7X6X5X4X3X2X1X0X data byte
3Y7Y6Y5Y4Y3Y2Y1Y0Y data bytes
4Z7Z6Z5Z4Z3Z2Z1Z0Z/wheel data byte

Standard PS/2-compatible mouse data packet format (5 Buttons + VerticalWheel)

ByteD7D6D5D4D3D2D1D0Comment
100YsignXsign1MRLX/Y signs and R/L/M buttons
2X7X6X5X4X3X2X1X0X data byte
3Y7Y6Y5Y4Y3Y2Y1Y0Y data bytes
400B5B4Z3Z2Z1Z0Z/wheel data and buttons 4 and 5

Important

Notice that the Z/wheel data for a 5-button wheel mouse has been reduced to four bits instead of the 8 bits used in the IntelliMouse-compatible 3-button wheel mode. This reduction is made possible by the fact that the wheel typically cannot generate values beyond the range +7/-8 during any given interrupt period. Windows mouse drivers will sign extend the four Z/wheel data bits when the mouse is in the 5-button wheel mode, and the full Z/wheel data byte when the mouse operates in the 3-button wheel mode.

Buttons 4 & 5 on are mapped to WM_APPCOMMAND messages and correspond to App_Back and App_Forward.

Devices not requiring vendor drivers

Vendor drivers are not required for the following devices:

  • Devices that comply with the HID Standard.
  • Keyboard, mouse, or game port devices operated by the system-supplied non-HIDClass drivers.

Kbfiltr sample

Kbfiltr is designed to be used with Kbdclass, the system class driver for keyboard devices and I8042prt, the function driver for a PS/2-style keyboard. Kbfiltr demonstrates how to filter I/O requests and how to add callback routines that modify the operation of Kbdclass and I8042prt.

For more information about Kbfiltr operation, see the following:

  • The ntddkbd.h WDK header file.

  • The sample Kbfiltr source code.

Kbfiltr IOCTLs

IOCTL_INTERNAL_I8042_HOOK_KEYBOARD

The IOCTL_INTERNAL_I8042_HOOK_KEYBOARD request does the following:

  • Adds an initialization callback routine to the I8042prt keyboard initialization routine.
  • Adds an ISR callback routine to the I8042prt keyboard ISR.

The initialization and ISR callbacks are optional and are provided by an upper-level filter driver for a PS/2-style keyboard device.

After I8042prt receives an IOCTL_INTERNAL_KEYBOARD_CONNECT request, it sends a synchronous IOCTL_INTERNAL_I8042_HOOK_KEYBOARD request to the top of the keyboard device stack.

After Kbfiltr receives the hook keyboard request, Kbfiltr filters the request in the following way:

  • Saves the upper-level information passed to Kbfiltr, which includes the context of an upper-level device object, a pointer to an initialization callback, and a pointer to an ISR callback.
  • Replaces the upper-level information with its own.
  • Saves the context of I8042prt and pointers to callbacks that the Kbfiltr ISR callback can use.

IOCTL_INTERNAL_KEYBOARD_CONNECT

The IOCTL_INTERNAL_KEYBOARD_CONNECT request connects the Kbdclass service to the keyboard device. Kbdclass sends this request down the keyboard device stack before it opens the keyboard device.

After Kbfiltr received the keyboard connect request, Kbfiltr filters the connect request in the following way:

  • Saves a copy of Kbdclass's CONNECT_DATA (Kbdclass) structure that is passed to the filter driver by Kbdclass.
  • Substitutes its own connect information for the class driver connect information.
  • Sends the IOCTL_INTERNAL_KEYBOARD_CONNECT request down the device stack.

If the request is not successful, Kbfiltr completes the request with an appropriate error status.

Kbfiltr provides a template for a filter service callback routine that can supplement the operation of KeyboardClassServiceCallback, the Kbdclass class service callback routine. The filter service callback can filter the input data that is transferred from the device input buffer to the class data queue.

IOCTL_INTERNAL_KEYBOARD_DISCONNECT

The IOCTL_INTERNAL_KEYBOARD_DISCONNECT request is completed with a status of STATUS_NOT_IMPLEMENTED. Note that a Plug and Play keyboard can be added or removed by the Plug and Play manager.

For all other device control requests, Kbfiltr skips the current IRP stack and sends the request down the device stack without further processing.

Callback routines implemented by Kbfiltr

KbFilter_InitializationRoutine

See PI8042_KEYBOARD_INITIALIZATION_ROUTINE

The KbFilter_InitializationRoutine is not needed if the I8042prt default initialization of a keyboard is sufficient.

I8042prt calls KbFilter_InitializationRoutine when it initializes the keyboard. Default keyboard initialization includes the following operations:

  • reset the keyboard
  • set the typematic rate and delay
  • set the light-emitting diodes (LED)

KbFilter_IsrHook

See PI8042_KEYBOARD_ISR. This callback is not needed if the default operation of I8042prt is sufficient.

The I8042prt keyboard ISR calls KbFilter_IsrHook after it validates the interrupt and reads the scan code.

KbFilter_IsrHook runs in kernel mode at the IRQL of the I8042prt keyboard.

KbFilter_ServiceCallback

See PSERVICE_CALLBACK_ROUTINE.

The ISR dispatch completion routine of the function driver calls KbFilter_ServiceCallback, which then calls the keyboard class driver's implementation of PSERVICE_CALLBACK_ROUTINE. A vendor can implement a filter service callback to modify the input data that is transferred from the device's input buffer to the class data queue. For example, the callback can delete, transform, or insert data.

Moufiltr sample

Moufiltr is designed to be used with Mouclass, the system class driver for mouse devices used with Windows 2000 and later versions, and I8042prt, the function driver for a PS/2-style mouse used with Windows 2000 and later. Moufiltr demonstrates how to filter I/O requests and add callback routines that modify the operation of Mouclass and I8042prt.

For more information about Moufiltr operation, see the following:

  • The ntddmou.h WDK header file.

  • The sample Moufiltr source code.

Moufiltr control codes

IOCTL_INTERNAL_I8042_HOOK_MOUSE

The IOCTL_INTERNAL_I8042_HOOK_MOUSE request adds an ISR callback routine to the I8042prt mouse ISR. The ISR callback is optional and is provided by an upper-level mouse filter driver.

I8042prt sends this request after it receives an IOCTL_INTERNAL_MOUSE_CONNECT request. I8042prt sends a synchronous IOCTL_INTERNAL_I8042_HOOK_MOUSE request to the top of the mouse device stack.

After Moufiltr receives the hook mouse request, it filters the request in the following way:

  • Saves the upper-level information passed to Moufiltr, which includes the context of an upper-level device object and a pointer to an ISR callback.
  • Replaces the upper-level information with its own.
  • Saves the context of I8042prt and pointers to callbacks that the Moufiltr ISR callbacks can use.

Moufiltr Callback Routines

IOCTL_INTERNAL_MOUSE_CONNECT

Microsoft Keyboards Drivers

The IOCTL_INTERNAL_MOUSE_CONNECT request connects Mouclass service to a mouse device.

IOCTL_INTERNAL_MOUSE_DISCONNECT

The IOCTL_INTERNAL_MOUSE_DISCONNECT request is completed by Moufiltr with an error status of STATUS_NOT_IMPLEMENTED.

For all other requests, Moufiltr skips the current IRP stack and sends the request down the device stack without further processing.

Microsoft Keyboard Drivers

Callback routines

MouFilter_IsrHook

See PI8042_MOUSE_ISR.

A MouFilter_IsrHook callback is not needed if the default operation of I8042prt is sufficient.

The I8042prt mouse ISR calls MouFilter_IsrHook after it validates the interrupt.

To reset a mouse, I8042prt goes through a sequence of operational substates, each one of which is identified by an MOUSE_RESET_SUBSTATE enumeration value. For more information about how I8042prt resets a mouse and the corresponding mouse reset substates, see the documentation of MOUSE_RESET_SUBSTATE in ntdd8042.h.

MouFilter_IsrHook runs in kernel mode at the IRQL of the I8042prt mouse ISR.

MouFilter_ServiceCallback

See PSERVICE_CALLBACK_ROUTINE

The ISR DPC of I8042prt calls MouFilter_ServiceCallback, which then calls MouseClassServiceCallback. A filter service callback can be configured to modify the input data that is transferred from the device's input buffer to the class data queue. For example, the callback can delete, transform, or insert data.