Files
punktfunk/packaging/windows/drivers/pf-vdisplay/src/monitor.rs
T
enricobuehler 2f9f26de8c refactor(windows-drivers): pod_init! macro — 27 unsafe { mem::zeroed() } POD inits -> 1 (Goal-3 #3)
The driver zero-initialised C POD structs (IddCx/WDF descriptors) with 27
scattered `let mut x: T = unsafe { core::mem::zeroed() };`, each carrying its own
`// SAFETY` about the all-zero bit pattern being valid + the caller setting `.Size`
etc. right after.

Replace with one `pod_init!(T)` macro (in log.rs, reachable everywhere via the
existing `#[macro_use] mod log;` — same mechanism as `dbglog!`) that owns the
single `unsafe { zeroed::<T>() }` + the SAFETY rationale. All 27 sites
(adapter 6, callbacks 3, entry 4, monitor 10, swap_chain_processor 4) now read
`let mut x = pod_init!(T)`. Zero behavior change (mem::zeroed semantics identical);
the type is passed explicitly so no inference depends on the removed annotation.

27 `unsafe` blocks → 1. Driver still `deny(unsafe_op_in_unsafe_fn)`-clean (the
macro expands to an explicit `unsafe {}`; the one nested-in-user-unsafe site is
fine — no `unused_unsafe` for macro-generated blocks). Driver-only (CI-gated);
adversarially reviewed (macro scoping, all sites, no leftover raw zeroed).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
2026-06-26 06:01:02 +00:00

521 lines
22 KiB
Rust

//! Virtual-monitor model + lifecycle (STEP 4). Monitors are created on demand by the control plane
//! ([`crate::control`], `IOCTL_ADD`): each carries the requested mode (advertised as preferred) plus the
//! `session_id` the host keys it by and the OS target id + render-adapter LUID captured at arrival. Ported
//! from the working upstream virtual-display-rs (`monitor.rs` + `context.rs::create_monitor`), with
//! `guid: u128` → `session_id: u64` for the owned `pf_driver_proto` control plane.
use std::sync::Mutex;
use std::time::{Duration, Instant};
use wdk_sys::iddcx;
/// One resolution with the refresh rates it supports.
#[derive(Clone)]
pub struct Mode {
pub width: u32,
pub height: u32,
pub refresh_rates: Vec<u32>,
}
/// A single (width, height, refresh) tuple — modes flattened across their refresh rates.
#[derive(Copy, Clone)]
pub struct ModeItem {
pub width: u32,
pub height: u32,
pub refresh_rate: u32,
}
/// Flatten a mode list into per-refresh-rate tuples (the order the mode DDIs emit).
pub fn flatten(modes: &[Mode]) -> impl Iterator<Item = ModeItem> + '_ {
modes.iter().flat_map(|m| {
m.refresh_rates.iter().map(|&rr| ModeItem {
width: m.width,
height: m.height,
refresh_rate: rr,
})
})
}
/// A live (or pending) virtual monitor.
pub struct MonitorObject {
/// The IddCx monitor handle, set once `IddCxMonitorCreate` returns (None while pending).
pub object: Option<iddcx::IDDCX_MONITOR>,
/// EDID serial / connector index — the key the mode DDIs match on.
pub id: u32,
/// Advertised modes (requested mode first, then [`default_modes`]).
pub modes: Vec<Mode>,
/// The host's monotonic key (ADD/REMOVE).
pub session_id: u64,
/// OS target id + render-adapter LUID from `IDARG_OUT_MONITORARRIVAL` (the ADD reply).
pub target_id: u32,
pub adapter_luid_low: u32,
pub adapter_luid_high: i32,
/// The live swap-chain drain worker, set by `assign_swap_chain` and dropped (RAII-joins the worker
/// thread) by `unassign_swap_chain` / departure (STEP 5).
pub swap_chain_processor: Option<crate::swap_chain_processor::SwapChainProcessor>,
/// When the entry was created — the watchdog skips still-initializing monitors.
pub created_at: Instant,
}
// SAFETY: the raw IddCx monitor handle is framework-managed; access is serialized by MONITOR_MODES.
unsafe impl Send for MonitorObject {}
/// All live monitors. A process-`static` (not a WDFDEVICE-context-owned allocation) BY NECESSITY: the IddCx
/// monitor/mode DDIs receive only an IddCx handle — never the WDFDEVICE or its context — so this state must
/// be reachable without one (the upstream virtual-display-rs is a process-`static` for the same reason).
/// With a single `pf_vdisplay` devnode + `UmdfHostProcessSharing=ProcessSharingDisabled` the host process
/// (and this state) die WITH the device, so it is effectively device-scoped already; a `Box` + `AtomicPtr`
/// "device-owned" variant (audit §2.5) would only add a use-after-free window — the host-gone watchdog
/// thread ([`crate::control::start_watchdog`]) races device cleanup — for no real gain. Cleanup of the
/// heavy per-monitor resources on device removal is instead done explicitly ([`cleanup_for_device_removal`]).
pub static MONITOR_MODES: Mutex<Vec<MonitorObject>> = Mutex::new(Vec::new());
/// True if any virtual monitor currently exists — the host-gone watchdog only reaps when there's
/// something to reap (see [`crate::control::start_watchdog`]).
pub fn has_monitors() -> bool {
MONITOR_MODES.lock().map(|l| !l.is_empty()).unwrap_or(false)
}
/// Depart every monitor that has existed at least `grace` — the host-gone watchdog reap
/// ([`crate::control::start_watchdog`]). The grace skips a just-created monitor (the host adds it, then
/// starts pinging) so a momentarily-stale ping timer can't nuke a brand-new monitor. Returns the count
/// departed. Same lock discipline as [`remove_monitor`]: drop each worker (which RAII-joins its thread)
/// OUTSIDE the `MONITOR_MODES` lock, then depart.
pub fn reap_orphaned(grace: Duration) -> usize {
let mut drained: Vec<(
Option<iddcx::IDDCX_MONITOR>,
Option<crate::swap_chain_processor::SwapChainProcessor>,
)> = {
let Ok(mut lock) = MONITOR_MODES.lock() else {
return 0;
};
let mut taken = Vec::new();
let mut i = 0;
while i < lock.len() {
if lock[i].created_at.elapsed() >= grace {
let mut m = lock.remove(i);
taken.push((m.object, m.swap_chain_processor.take()));
} else {
i += 1;
}
}
taken
};
let n = drained.len();
for (_, processor) in &mut drained {
drop(processor.take());
}
for (object, _) in drained {
if let Some(m) = object {
// SAFETY: `m` is a live IddCx monitor handle; departure tears it down.
unsafe { wdk_iddcx::IddCxMonitorDeparture(m) };
}
}
n
}
/// Fallback modes appended after the requested mode, so a topology change still has options.
fn default_modes() -> Vec<Mode> {
vec![
Mode {
width: 1920,
height: 1080,
refresh_rates: vec![60, 120],
},
Mode {
width: 1280,
height: 720,
refresh_rates: vec![60],
},
]
}
/// `DISPLAYCONFIG_VIDEO_SIGNAL_INFO` for a monitor mode (vSyncFreqDivider = 0, per the DDI contract).
pub fn display_info(
width: u32,
height: u32,
refresh_rate: u32,
) -> wdk_sys::DISPLAYCONFIG_VIDEO_SIGNAL_INFO {
// Compute in u64 then saturate the u32 rational numerators: the old u32 `refresh*(h+4)^2` overflows
// for a large mode (e.g. 8K@240), which panics→aborts the extern-"C" mode DDI in a debug build.
// Identical for every real mode; only an absurd (also now bounds-rejected) mode saturates.
let clock_rate: u64 = u64::from(refresh_rate) * u64::from(height + 4) * u64::from(height + 4) + 1000;
let clock_rate_u32 = u32::try_from(clock_rate).unwrap_or(u32::MAX);
let mut si = pod_init!(wdk_sys::DISPLAYCONFIG_VIDEO_SIGNAL_INFO);
si.pixelRate = clock_rate;
si.hSyncFreq = wdk_sys::DISPLAYCONFIG_RATIONAL {
Numerator: clock_rate_u32,
Denominator: height + 4,
};
si.vSyncFreq = wdk_sys::DISPLAYCONFIG_RATIONAL {
Numerator: clock_rate_u32,
Denominator: (height + 4) * (height + 4),
};
si.activeSize = wdk_sys::DISPLAYCONFIG_2DREGION {
cx: width,
cy: height,
};
si.totalSize = wdk_sys::DISPLAYCONFIG_2DREGION {
cx: width + 4,
cy: height + 4,
};
// union { AdditionalSignalInfo bitfield | videoStandard:u32 }: videoStandard=255, vSyncFreqDivider=0.
si.__bindgen_anon_1.videoStandard = 255;
si.scanLineOrdering =
wdk_sys::DISPLAYCONFIG_SCANLINE_ORDERING::DISPLAYCONFIG_SCANLINE_ORDERING_PROGRESSIVE;
si
}
/// `IDDCX_TARGET_MODE` for a scan-out mode (vSyncFreqDivider = 1, per the DDI contract).
pub fn target_mode(width: u32, height: u32, refresh_rate: u32) -> iddcx::IDDCX_TARGET_MODE {
let region = wdk_sys::DISPLAYCONFIG_2DREGION {
cx: width,
cy: height,
};
let mut si = pod_init!(wdk_sys::DISPLAYCONFIG_VIDEO_SIGNAL_INFO);
si.pixelRate = u64::from(refresh_rate) * u64::from(width) * u64::from(height);
si.hSyncFreq = wdk_sys::DISPLAYCONFIG_RATIONAL {
Numerator: refresh_rate * height,
Denominator: 1,
};
si.vSyncFreq = wdk_sys::DISPLAYCONFIG_RATIONAL {
Numerator: refresh_rate,
Denominator: 1,
};
si.totalSize = region;
si.activeSize = region;
si.scanLineOrdering =
wdk_sys::DISPLAYCONFIG_SCANLINE_ORDERING::DISPLAYCONFIG_SCANLINE_ORDERING_PROGRESSIVE;
// videoStandard=255, vSyncFreqDivider=1 (bits 16..21) => 255 | (1<<16).
si.__bindgen_anon_1.videoStandard = 255 | (1 << 16);
let mut tm = pod_init!(iddcx::IDDCX_TARGET_MODE);
tm.Size = core::mem::size_of::<iddcx::IDDCX_TARGET_MODE>() as u32;
tm.TargetVideoSignalInfo = wdk_sys::DISPLAYCONFIG_TARGET_MODE {
targetVideoSignalInfo: si,
};
tm
}
/// Wire bit-depth advertised per mode in the `*2` (HDR) mode DDIs. STEP 7: advertise BOTH 8 and 10 bpc
/// RGB (so the OS offers HDR10 modes), no YCbCr. The wdk-sys bindgen enum is `ModuleConsts`, so each
/// `IDDCX_BITS_PER_COMPONENT_*` is a plain-int const and the `IDDCX_WIRE_BITS_PER_COMPONENT` fields are
/// plain ints — OR the constants directly (NO newtype `.0` like the oracle's wdf-umdf-sys binding). Field
/// names (Rgb/YCbCr444/YCbCr422/YCbCr420, IDDCX_BITS_PER_COMPONENT_8/_10/_NONE) are the verbatim C header
/// names, identical across both bindings.
pub fn wire_bits() -> iddcx::IDDCX_WIRE_BITS_PER_COMPONENT {
let rgb = iddcx::IDDCX_BITS_PER_COMPONENT::IDDCX_BITS_PER_COMPONENT_8
| iddcx::IDDCX_BITS_PER_COMPONENT::IDDCX_BITS_PER_COMPONENT_10;
let mut w = pod_init!(iddcx::IDDCX_WIRE_BITS_PER_COMPONENT);
w.Rgb = rgb;
w.YCbCr444 = iddcx::IDDCX_BITS_PER_COMPONENT::IDDCX_BITS_PER_COMPONENT_NONE;
w.YCbCr422 = iddcx::IDDCX_BITS_PER_COMPONENT::IDDCX_BITS_PER_COMPONENT_NONE;
w.YCbCr420 = iddcx::IDDCX_BITS_PER_COMPONENT::IDDCX_BITS_PER_COMPONENT_NONE;
w
}
/// `IDDCX_TARGET_MODE2` for a scan-out mode (HDR `*2` path): builds the v1 [`target_mode`] and copies its
/// `TargetVideoSignalInfo`, then stamps the `*2` Size + per-mode wire bit-depth ([`wire_bits`]). Rest
/// zeroed.
pub fn target_mode2(width: u32, height: u32, refresh_rate: u32) -> iddcx::IDDCX_TARGET_MODE2 {
let m1 = target_mode(width, height, refresh_rate);
let mut tm = pod_init!(iddcx::IDDCX_TARGET_MODE2);
tm.Size = core::mem::size_of::<iddcx::IDDCX_TARGET_MODE2>() as u32;
tm.TargetVideoSignalInfo = m1.TargetVideoSignalInfo;
tm.BitsPerComponent = wire_bits();
tm
}
/// A monitor's advertised modes (the looked-up entry returns a clone for lock-free mode-DDI fill).
pub fn modes_for_id(id: u32) -> Option<Vec<Mode>> {
MONITOR_MODES
.lock()
.ok()?
.iter()
.find(|m| m.id == id)
.map(|m| m.modes.clone())
}
/// Modes for the monitor whose handle matches (used by `monitor_query_modes`).
pub fn modes_for_object(object: iddcx::IDDCX_MONITOR) -> Option<Vec<Mode>> {
MONITOR_MODES
.lock()
.ok()?
.iter()
.find(|m| m.object == Some(object))
.map(|m| m.modes.clone())
}
/// The OS target id stamped on the monitor whose handle matches (used by `assign_swap_chain` to name the
/// shared-ring objects). `None` if the monitor isn't found.
pub fn target_id_for_object(object: iddcx::IDDCX_MONITOR) -> Option<u32> {
MONITOR_MODES
.lock()
.ok()?
.iter()
.find(|m| m.object == Some(object))
.map(|m| m.target_id)
}
/// Install a swap-chain processor on the monitor whose handle matches, returning any PREVIOUS processor
/// for the caller to drop OUTSIDE the lock. Dropping a processor RAII-joins its worker thread, so it must
/// never happen while holding `MONITOR_MODES` (the worker would block the whole control plane / risk a
/// self-deadlock). `None` returned if the monitor isn't found (the caller should drop `proc` itself).
#[must_use]
pub fn set_swap_chain_processor(
object: iddcx::IDDCX_MONITOR,
proc: crate::swap_chain_processor::SwapChainProcessor,
) -> Option<crate::swap_chain_processor::SwapChainProcessor> {
let Ok(mut lock) = MONITOR_MODES.lock() else {
return Some(proc);
};
if let Some(m) = lock.iter_mut().find(|m| m.object == Some(object)) {
m.swap_chain_processor.replace(proc)
} else {
// No such monitor — hand `proc` back so the caller drops it (joins the worker) outside the lock.
Some(proc)
}
}
/// Take (remove) the swap-chain processor from the monitor whose handle matches, returning it for the
/// caller to drop OUTSIDE the lock (see `set_swap_chain_processor`). `None` if none was installed.
#[must_use]
pub fn take_swap_chain_processor(
object: iddcx::IDDCX_MONITOR,
) -> Option<crate::swap_chain_processor::SwapChainProcessor> {
MONITOR_MODES
.lock()
.ok()?
.iter_mut()
.find(|m| m.object == Some(object))?
.swap_chain_processor
.take()
}
/// `IOCTL_ADD`: create + arrive a virtual monitor at `width`x`height`@`refresh`. Returns the OS
/// `(target_id, adapter_luid_low, adapter_luid_high)` for the [`AddReply`](pf_driver_proto::control::AddReply),
/// or `None` on failure (no adapter yet / IddCx error).
pub fn create_monitor(
session_id: u64,
width: u32,
height: u32,
refresh: u32,
) -> Option<(u32, u32, i32)> {
let adapter = crate::adapter::adapter()?;
// Single identity per session (E1): if the host re-ADDs a still-live `session_id` (it shouldn't), depart
// the stale monitor first, so one session maps to exactly one monitor (no duplicate EDID/target lingers).
if MONITOR_MODES
.lock()
.map(|l| l.iter().any(|m| m.session_id == session_id))
.unwrap_or(false)
{
dbglog!("[pf-vd] create_monitor: session {session_id} already live — departing the stale monitor");
remove_monitor(session_id);
}
let mut modes = vec![Mode {
width,
height,
refresh_rates: vec![refresh],
}];
modes.extend(default_modes());
// Register the (pending) monitor so the mode DDIs can find it by EDID-serial id before arrival, under a
// REUSED id (the lowest not currently live). Reclaiming the id on REMOVE — instead of a monotonic
// counter — keeps the connector index / EDID serial / container GUID bounded, so IddCx reuses the same
// OS target slot on a fresh ADD rather than leaving a ghost monitor node behind (the slot-exhaustion
// wedge: sustained ADD/REMOVE churn eventually makes ADD fail 0x80070490 ERROR_NOT_FOUND). Allocated
// under the lock with the push so two concurrent ADDs can't pick the same id.
let id = {
let Ok(mut lock) = MONITOR_MODES.lock() else {
return None;
};
let id = alloc_monitor_id(&lock);
lock.push(MonitorObject {
object: None,
id,
modes,
session_id,
target_id: 0,
adapter_luid_low: 0,
adapter_luid_high: 0,
swap_chain_processor: None,
created_at: Instant::now(),
});
id
};
// EDID (serial = id) describes the monitor; the OS calls back into parse_monitor_description.
let mut edid = crate::edid::Edid::generate_with(id);
let mut desc = pod_init!(iddcx::IDDCX_MONITOR_DESCRIPTION);
desc.Size = core::mem::size_of::<iddcx::IDDCX_MONITOR_DESCRIPTION>() as u32;
desc.Type = iddcx::IDDCX_MONITOR_DESCRIPTION_TYPE::IDDCX_MONITOR_DESCRIPTION_TYPE_EDID;
desc.DataSize = edid.len() as u32;
// SAFETY: `edid` is a local Vec that outlives this `create_monitor` call; IddCxMonitorCreate (below)
// reads through `pData` SYNCHRONOUSLY, before `edid` drops — the pointer never escapes the call.
desc.pData = edid.as_mut_ptr().cast();
let mut info = pod_init!(iddcx::IDDCX_MONITOR_INFO);
info.Size = core::mem::size_of::<iddcx::IDDCX_MONITOR_INFO>() as u32;
info.MonitorContainerId = container_guid(id);
info.MonitorType =
wdk_sys::DISPLAYCONFIG_VIDEO_OUTPUT_TECHNOLOGY::DISPLAYCONFIG_OUTPUT_TECHNOLOGY_HDMI;
info.ConnectorIndex = id;
info.MonitorDescription = desc;
let mut attr = pod_init!(wdk_sys::WDF_OBJECT_ATTRIBUTES);
attr.Size = core::mem::size_of::<wdk_sys::WDF_OBJECT_ATTRIBUTES>() as u32;
attr.ExecutionLevel = wdk_sys::_WDF_EXECUTION_LEVEL::WdfExecutionLevelInheritFromParent;
attr.SynchronizationScope =
wdk_sys::_WDF_SYNCHRONIZATION_SCOPE::WdfSynchronizationScopeInheritFromParent;
let create_in = iddcx::IDARG_IN_MONITORCREATE {
ObjectAttributes: &raw mut attr,
pMonitorInfo: &raw mut info,
};
let mut create_out = pod_init!(iddcx::IDARG_OUT_MONITORCREATE);
// SAFETY: adapter is a valid IddCx adapter; create_in points to valid local storage read synchronously.
let st = unsafe { wdk_iddcx::IddCxMonitorCreate(adapter, &create_in, &mut create_out) };
dbglog!("[pf-vd] IddCxMonitorCreate(id={id}) -> {st:#x}");
if !wdk_iddcx::nt_success(st) {
remove_by_id(id);
return None;
}
let monitor = create_out.MonitorObject;
if let Ok(mut lock) = MONITOR_MODES.lock() {
if let Some(m) = lock.iter_mut().find(|m| m.id == id) {
m.object = Some(monitor);
}
}
// Tell the OS the monitor is plugged in.
let mut arrival_out = pod_init!(iddcx::IDARG_OUT_MONITORARRIVAL);
// SAFETY: `monitor` is the just-created IddCx monitor handle.
let st = unsafe { wdk_iddcx::IddCxMonitorArrival(monitor, &mut arrival_out) };
dbglog!("[pf-vd] IddCxMonitorArrival(id={id}) -> {st:#x}");
if !wdk_iddcx::nt_success(st) {
return None;
}
let (target_id, luid_low, luid_high) = (
arrival_out.OsTargetId,
arrival_out.OsAdapterLuid.LowPart,
arrival_out.OsAdapterLuid.HighPart,
);
if let Ok(mut lock) = MONITOR_MODES.lock() {
if let Some(m) = lock.iter_mut().find(|m| m.id == id) {
m.target_id = target_id;
m.adapter_luid_low = luid_low;
m.adapter_luid_high = luid_high;
}
}
Some((target_id, luid_low, luid_high))
}
/// `IOCTL_REMOVE`: depart + drop the monitor for `session_id`. Returns true if one was removed.
pub fn remove_monitor(session_id: u64) -> bool {
// Pull out the IddCx handle AND the swap-chain processor under the lock, but drop the processor
// (which RAII-joins its worker thread) only AFTER the lock guard is released — joining a worker
// while holding `MONITOR_MODES` would head-block the whole control plane / risk a self-deadlock.
let (monitor, processor) = {
let Ok(mut lock) = MONITOR_MODES.lock() else {
return false;
};
let Some(pos) = lock.iter().position(|m| m.session_id == session_id) else {
return false;
};
let mut entry = lock.remove(pos);
(entry.object, entry.swap_chain_processor.take())
};
// Drop the worker FIRST (it joins + deletes the swap-chain), THEN depart the monitor.
drop(processor);
if let Some(m) = monitor {
// SAFETY: `m` is a live IddCx monitor handle; departure tears it down.
unsafe { wdk_iddcx::IddCxMonitorDeparture(m) };
}
true
}
/// `IOCTL_CLEAR_ALL`: depart + drop every monitor (host-startup orphan reap).
pub fn clear_all() {
// Drain every entry under the lock, keeping each (handle, processor); drop the processors (RAII-join
// their workers) only AFTER releasing the lock, then depart the monitors. See `remove_monitor`.
let mut drained: Vec<(
Option<iddcx::IDDCX_MONITOR>,
Option<crate::swap_chain_processor::SwapChainProcessor>,
)> = {
let Ok(mut lock) = MONITOR_MODES.lock() else {
return;
};
lock.drain(..)
.map(|mut m| (m.object, m.swap_chain_processor.take()))
.collect()
};
// Drop all workers FIRST (join + delete their swap-chains), THEN depart the monitors.
for (_, processor) in &mut drained {
drop(processor.take());
}
for (object, _) in drained {
if let Some(m) = object {
// SAFETY: `m` is a live IddCx monitor handle.
unsafe { wdk_iddcx::IddCxMonitorDeparture(m) };
}
}
}
/// `EvtCleanupCallback` (device removal, [`crate::callbacks::device_cleanup`]): drop every monitor's heavy
/// resources — the swap-chain processor workers (each RAII-joins its thread + deletes its swap-chain) — and
/// clear the list, WITHOUT `IddCxMonitorDeparture` (the framework tears the IddCx monitors down together
/// with the departing device; departing here would double-tear). Frees our worker threads promptly even
/// though the per-devnode WUDFHost (`ProcessSharingDisabled`) would also reap them when it exits.
pub fn cleanup_for_device_removal() {
let mut drained: Vec<Option<crate::swap_chain_processor::SwapChainProcessor>> = {
let Ok(mut lock) = MONITOR_MODES.lock() else {
return;
};
lock.drain(..)
.map(|mut m| m.swap_chain_processor.take())
.collect()
};
// Drop the workers (join their threads) AFTER releasing the lock — joining under MONITOR_MODES would
// head-block the control plane (same discipline as remove_monitor / clear_all).
for processor in &mut drained {
drop(processor.take());
}
}
/// Drop a pending entry by id (create failed before arrival).
fn remove_by_id(id: u32) {
if let Ok(mut lock) = MONITOR_MODES.lock() {
lock.retain(|m| m.id != id);
}
}
/// The lowest monitor id (≥1) not currently live. Reusing freed ids (instead of a monotonic counter) keeps
/// the connector index / EDID serial / container GUID bounded to the number of concurrent monitors, so a
/// fresh ADD reuses a departed monitor's OS target slot rather than allocating a new one and orphaning the
/// old (the ghost-monitor accumulation that wedges ADD at 0x80070490 ERROR_NOT_FOUND). Caller holds
/// `MONITOR_MODES`. With ≤ N live ids, a free one always exists in `1..=N+1` (pigeonhole).
fn alloc_monitor_id(modes: &[MonitorObject]) -> u32 {
(1u32..=modes.len() as u32 + 1)
.find(|id| !modes.iter().any(|m| m.id == *id))
.unwrap_or(1)
}
/// A deterministic, monitor-unique container GUID (groups targets into a physical device). Derived from
/// `id` so it is stable + collision-free without a random source.
fn container_guid(id: u32) -> wdk_sys::GUID {
wdk_sys::GUID {
Data1: 0x7066_7664u32.wrapping_add(id),
Data2: 0x7044,
Data3: 0x5350,
Data4: [
0xa1,
0xb2,
0xc3,
0xd4,
0xe5,
0xf6,
(id >> 8) as u8,
id as u8,
],
}
}