Specifying the Reflector in an INF File

Starting in Windows 11, the recommended way to add the reflector (WUDFRd.sys) to the kernel-mode device stack is to reference the system-supplied WudfRd.inf file in the INF file of a UMDF driver.

On Windows 10 and earlier, to add the reflector (WUDFRd.sys), the INF file of a UMDF driver must include an AddService directive in an INF DDInstall.Services section as well as a service-install-section. While this method still works on Windows 11 and later, it is not recommended.

In both methods, the reflector can be an upper filter, a lower filter, or the service for the device, depending on the configuration of the user-mode stack.

Referencing WudfRd.inf (Windows 11 and later)

You can find a sample INF that uses this technique at echoum.inx. Alternatively, use one of the following snippets.

To install the WudfRd service as the function driver for the device:

[DDInstall]
Include=WUDFRD.inf
Needs=WUDFRD.NT
; also include any existing DDInstall directives

[DDInstall.HW]
Include=WUDFRD.inf
Needs=WUDFRD.NT.HW
; also include any existing DDInstall.HW directives

[DDInstall.Services]
Include=WUDFRD.inf
Needs=WUDFRD.NT.Services
; also include any existing any DDInstall.Services directives

To install the WudfRd service as an upper filter driver:

[DDInstall] 
Include=WUDFRD.inf
Needs=WUDFRD_UpperFilter.NT
; also include any existing DDInstall directives

[DDInstall.HW]
Include=WUDFRD.inf
Needs=WUDFRD_UpperFilter.NT.HW
; also include any existing DDInstall.HW directives

[DDInstall.Services]
Include=WUDFRD.inf
Needs=WUDFRD_UpperFilter.NT.Services
; also include any existing any DDInstall.Services directives

[DDInstall.Filters]
Include=WUDFRD.inf
Needs=WUDFRD_UpperFilter.NT.Filters

To install the WudfRd service as a lower filter driver:

[DDInstall] 
Include=WUDFRD.inf
Needs=WUDFRD_LowerFilter.NT
; also include any existing DDInstall directives

[DDInstall.HW]
Include=WUDFRD.inf
Needs=WUDFRD_LowerFilter.NT.HW
; also include any existing DDInstall.HW directives

[DDInstall.Services]
Include=WUDFRD.inf
Needs=WUDFRD_LowerFilter.NT.Services
; also include any existing any DDInstall.Services directives

[DDInstall.Filters]
Include=WUDFRD.inf
Needs=WUDFRD_LowerFilter.NT.Filters

Using an AddService directive (Windows 10 and earlier)

The following code example shows how the INF file for a UMDF function driver might add the reflector.

[Skeleton_Install.Services]
AddService=WUDFRd,0x000001fa,WUDFRD_ServiceInstall

In this example, the driver specifies the 0x2 (SPSVCINST_ASSOCSERVICE) flag (ORed into the flags parameter above) to assign the reflector as the function driver in the kernel-mode device stack.

The AddService directive also sets the 0x000001f8 flags to prevent overwriting any preexisting configuration for the service. For more information about these flags, see the flags parameter of the AddService directive.

The following code example, taken from the WUDFVhidmini sample, shows an AddService directive for a UMDF filter driver.

[hidumdf.win8.NT.Services]
AddService=WUDFRd,0x000001f8,WUDFRD_ServiceInstall  
AddService=mshidumdf, 0x000001fa, mshidumdf.AddService

[WudfVhidmini_AddReg]
HKR,,"LowerFilters",0x00010008,"WUDFRd" ; FLG_ADDREG_TYPE_MULTI_SZ | FLG_ADDREG_APPEND

In this case, the mshidumdf service is associated with the FDO for the device stack, and the reflector is a lower filter.

Providing a service-install-section

The AddService directive references an service-install-section similar to the following code example. The ServiceType entry specifies 1 or 0x00000001, which indicates that the INF installs support for one or more devices. The StartType entry specifies when to start the driver. The ErrorControl entry specifies the level of error control that the driver provides. The ServiceBinary entry specifies the path to the binary (the reflector) for the service.

[WUDFRD_ServiceInstall]
DisplayName = "Windows Driver Frameworks - User-mode Driver Framework Reflector"
ServiceType=1
StartType=3
ErrorControl=1
ServiceBinary=%12%\WUDFRd.sys