feat(windows-drivers): IddCx link probe — call init DDIs via table dispatch

First USE of the iddcx binding: a minimal table-dispatch (src/iddcx_rt.rs) over
wdk_sys::iddcx — IddFunctions[_IDDFUNCENUM::<Name>TableIndex] cast to PFN_*,
IddDriverGlobals as implicit arg 1 (the WDF model; ModuleConsts i32 index, not the
oracle NewType .0). The probe EvtDeviceAdd now calls IddCxDeviceInitConfig →
WdfDeviceCreate → IddCxDeviceInitialize → IddCxAdapterInitAsync, exports
IddMinimumVersionRequired=4, and build.rs links IddCxStub (globbed from the SDK
Lib dir that ships iddcx). CI gate = compile + link IddCxStub.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

packaging/windows/drivers/wdk-probe/src/lib.rs

@@ -1,10 +1,14 @@
-//! Minimal UMDF2 driver — the M0/M1 toolchain + `/INTEGRITYCHECK` probe (see this crate's Cargo.toml).
-//! DriverEntry → WdfDriverCreate → (EvtDeviceAdd) WdfDeviceCreate: enough to exercise the wdk-sys WDF
-//! stub link without any device logic. Also force-links the shared `pf-vdisplay-proto` ABI crate to
-//! prove it compiles + links into a driver (no_std + bytemuck) across the workspace boundary.
+//! Minimal UMDF2 driver — the M0/M1 toolchain + `/INTEGRITYCHECK` + IddCx-binding probe (see this
+//! crate's Cargo.toml). DriverEntry → WdfDriverCreate → (EvtDeviceAdd) IddCxDeviceInitConfig →
+//! WdfDeviceCreate → IddCxDeviceInitialize → IddCxAdapterInitAsync: enough to exercise the wdk-sys WDF
+//! stub link AND prove the `iddcx` subset is callable + links against `IddCxStub`. Also force-links the
+//! shared `pf-vdisplay-proto` ABI crate (no_std + bytemuck) across the workspace boundary.
 
 #![allow(non_snake_case, clippy::missing_safety_doc)]
 
+mod iddcx_rt;
+
+use wdk_sys::iddcx::{IDARG_IN_ADAPTER_INIT, IDARG_OUT_ADAPTER_INIT, IDD_CX_CLIENT_CONFIG};
 use wdk_sys::{
     call_unsafe_wdf_function_binding, NTSTATUS, PCUNICODE_STRING, PDRIVER_OBJECT, PWDFDEVICE_INIT,
     ULONG, WDFDEVICE, WDFDRIVER, WDF_DRIVER_CONFIG, WDF_NO_HANDLE, WDF_NO_OBJECT_ATTRIBUTES,
@@ -17,6 +21,12 @@ const STATUS_SUCCESS: NTSTATUS = 0;
 #[used]
 static PROTO_GUID_LO: u64 = pf_vdisplay_proto::PF_VDISPLAY_INTERFACE_GUID_U128 as u64;
 
+/// IddCx (stub mode) requires the driver to export the minimum IddCx framework version it needs — the
+/// `#ifndef IDD_STUB` branch of `IddCxFuncEnum.h` (which normally emits it) is compiled out under
+/// `IDD_STUB`, so the driver provides it. `4` matches the proven `wdf-umdf` oracle.
+#[unsafe(no_mangle)]
+pub static IddMinimumVersionRequired: ULONG = 4;
+
 #[unsafe(export_name = "DriverEntry")]
 pub unsafe extern "system" fn driver_entry(
     driver: PDRIVER_OBJECT,
@@ -40,6 +50,16 @@ pub unsafe extern "system" fn driver_entry(
 }
 
 extern "C" fn evt_device_add(_driver: WDFDRIVER, mut device_init: PWDFDEVICE_INIT) -> NTSTATUS {
+    // Configure the device for IddCx BEFORE WdfDeviceCreate. The required `EvtIddCx*` callbacks are left
+    // null in this probe — its purpose is to prove the `iddcx` DDIs are callable and link against
+    // IddCxStub (CI), and that a self-signed IddCx driver loads + dispatches (box); the full callback
+    // surface + a valid adapter come with the driver port. At runtime IddCxDeviceInitConfig will reject
+    // the null callbacks, but the call site is what links IddCxStub and exercises table dispatch.
+    let mut cfg: IDD_CX_CLIENT_CONFIG = unsafe { core::mem::zeroed() };
+    cfg.Size = core::mem::size_of::<IDD_CX_CLIENT_CONFIG>() as ULONG;
+    // SAFETY: device_init is the framework-provided init; cfg is a valid (if minimal) config.
+    let _ = unsafe { iddcx_rt::IddCxDeviceInitConfig(device_init, &cfg) };
+
     let mut device: WDFDEVICE = core::ptr::null_mut();
     // SAFETY: device_init is the framework-provided init; attributes null; device receives the handle.
     let _ = unsafe {
@@ -50,5 +70,15 @@ extern "C" fn evt_device_add(_driver: WDFDRIVER, mut device_init: PWDFDEVICE_INI
             &mut device
         )
     };
+
+    // SAFETY: device is the just-created WDFDEVICE.
+    let _ = unsafe { iddcx_rt::IddCxDeviceInitialize(device) };
+
+    // SAFETY: zeroed adapter-init args — a link/dispatch reference, not a valid adapter (see above).
+    let in_args: IDARG_IN_ADAPTER_INIT = unsafe { core::mem::zeroed() };
+    let mut out_args: IDARG_OUT_ADAPTER_INIT = unsafe { core::mem::zeroed() };
+    // SAFETY: in/out args are valid local storage for the call.
+    let _ = unsafe { iddcx_rt::IddCxAdapterInitAsync(&in_args, &mut out_args) };
+
     STATUS_SUCCESS
 }