Roll My Own Windows Joystick HID Driver?

Question

I have a USB Joystick, and I want to write my own HID driver for it. Notably I want to inject delay between when the joystick input is received by Windows and when my application is notified of that input event. I would also like to change the identity of the joystick percieved by my application. I have never written a driver, let alone an HID driver, for Windows. Can anyone provide me with advice or pointers on how to go about doing this?

Answer 1

When you press knobs on the Joystick the electric signals reach the operating system (and onto the game) in the form of IRP's through the drivers chain. Intercepting these IRP's at some point and delaying the forwarding to the next driver can delay the joystick input. This can be achieved with driver filters.

To write windows drivers you need to use WinDDK.

The entrypoint of a windows driver is the DriverEntry function. In this function you will be hooking what IRP's you want to intercept and the callback functions that deal with them, in our case, the callback functions that delay the forwarding.

For example, say our IRP to be delayed is IRP_MJ_READ and our callback function is called CallbackDelayForwarding:

// the function that delays the IRP
NTSTATUS CallbackDelayForwarding(
    IN PDEVICE_OBJECT pDeviceObject, 
    IN PIRP pIrp
){
    // delay the forwarding
}

// this is the driver entrypoint, similar to "main" in user-mode executables
NTSTATUS DriverEntry(
    IN PDRIVER_OBJECT pDriverObject, 
    IN PUNICODE_STRING RegistryPath 
){
    pDriverObject->MajorFunction[IRP_MJ_READ] = CallbackDelayForwarding;
    ...
}

To delay the forwarding inside CallbackDelayForwarding, you must use functions from the KeInitializeTimer family to simulate some sort of sleep (maybe in conjunction with locks), KeDelayExecutionThread etc.

To install your filter driver in the joystick driver chain, you can use .inf files.

Check the toaster filter driver sample in the WinDDK, you can find it at INSTALL_DIR/src/general/toaster/ see also here.

Related links:
http://www.rootkit.com/newsread.php?newsid=187
http://www.techtalkz.com/microsoft-device-drivers/269654-toaster-filter-driver.html