feat: add linker args for VHF lib to wdk-build by Alan632 · Pull Request #653 · microsoft/windows-drivers-rs

Alan632 · 2026-05-01T23:38:30Z

Description

Add linker arguments for the VHF library to the build script output for each driver type so drivers using the VHF don't have to hardcode the output in their own build scripts.

wdk-build/lib.rs

For each driver type (WDM/KMDF/UMDF) add the correct Vhf lib linker arguments, gated by "hid" feature flag usage in wdk-sys.

Verification

Built a driver and ensured vhf linker args were still in build output after removing the hardcoded line in the driver's build.rs.

Copilot

Pull request overview

Adds an opt-in vhf feature to wdk-build so driver crates can automatically link the appropriate Virtual HID Framework (VHF) import library without hardcoding linker directives in their own build.rs.

Changes:

Add a vhf Cargo feature to wdk-build.
When vhf is enabled, emit VhfKm.lib for WDM/KMDF builds and VhfUm.lib for UMDF builds via build script output.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
`crates/wdk-build/src/lib.rs`	Emits VHF linker input per driver type under `#[cfg(feature = "vhf")]`.
`crates/wdk-build/Cargo.toml`	Defines the new `vhf` feature flag.

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codecov-commenter · 2026-05-02T00:03:20Z

Codecov Report

❌ Patch coverage is 90.00000% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 78.74%. Comparing base (efa6c11) to head (d22d9db).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
crates/wdk-build/src/lib.rs	90.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #653      +/-   ##
==========================================
+ Coverage   78.69%   78.74%   +0.04%     
==========================================
  Files          25       25              
  Lines        5234     5254      +20     
  Branches     5234     5254      +20     
==========================================
+ Hits         4119     4137      +18     
- Misses        995      997       +2     
  Partials      120      120

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…adata inspection (automatic) rather than crate features, removed vhf feature from Cargo.toml

Copilot

Pull request overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated 5 comments.

…ApiSubset enum

Copilot

Pull request overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated 3 comments.

Alan632 · 2026-05-08T01:21:14Z

+                    .enabled_api_subsets
+                    .iter()
+                    .any(|f| f == &ApiSubset::Hid)
+                {
+                    println!("cargo::rustc-cdylib-link-arg=VhfKm.lib");


Extended current config unit tests.

Copilot

Pull request overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated 5 comments.

…se contains

wmmc88 · 2026-05-08T17:12:24Z

    pub driver_config: DriverConfig,
+    /// List of features enabled for `wdk-sys` in resolved dependency graph
+    #[serde(default)]
+    enabled_api_subsets: Vec<ApiSubset>,


This should be a BTreeSet<ApiSubset> rather than a Vec. Each variant should appear at most once, and the three call sites that do iter().any(|f| f == &ApiSubset::Hid) collapse to contains(&ApiSubset::Hid). BTreeSet over HashSet keeps Config's Serialize/Deserialize round-trips deterministic (although we dont actually use this right now)

wmmc88 · 2026-05-08T17:12:24Z

+                             determined from cargo metadata resolve. Feature-dependent libraries \
+                             will not be linked automatically."
+                        );
+                        Vec::new()


the per-feature from_value(Value::String(f.clone())) is doing an unnecessary JSON round-trip and allocates/clones for every feature. Driving ApiSubset's existing Deserialize impl directly from &str via serde::de::IntoDeserializer avoids both:

use serde::de::{IntoDeserializer, value::{Error as ValueError, StrDeserializer}}; node.features .iter() .filter_map(|f| { ApiSubset::deserialize(f.as_str().into_deserializer()).ok() }) .collect()

actually, this should go further and actually filter some known set of cargo features that aren't APISubsets (ie. default, nightly), instead of relying on a deserialization failure

To clarify the second point - is the desire to have a set of known features (aka all wdk-sys features) and warn the user if something not in that set is found in the metadata?

If we have a set of known "non ApiSubset" features that we filter out without notifying the user about it, then that sounds similar to silently filtering out via deserialization failure?

we'd have a set of known non-api-subset features, and if we encounter one of those, it should hard error. anything thats not an api-subset feature and not in the known list should be treated as an unknown feature and we should bail. this is to help make sure at compile time that when there are new api subsets added, they map cleanly to the enum

wait, we should hard error on encountering non-api-subset features? (aka default, nightly, test-stubs) Shouldn't we just filter those out and only hard error on anything that isn't listed in the [features] section in wdk-sys's Cargo.toml? Otherwise build will fail if we enable a feature like default or nightly in wdk-sys

I went ahead and changed the implementation to hard error on found features that are neither in the non-api-subset-features list and the ApiSubset enum (eg. an unknown 'new' feature from wdk-sys), which I think is what we're both trying to express 😅 let's discuss offline if needed!

wmmc88 · 2026-05-08T17:12:24Z

    /// Build configuration of driver
    pub driver_config: DriverConfig,
+    /// List of features enabled for `wdk-sys` in resolved dependency graph
+    #[serde(default)]


Drop #[serde(default)] here. Nothing in the repo actually deserializes Config (all instances come from from_env_auto/new/default/struct literals; the line 554 serialization is metadata::Wdk, not Config), so this attribute has no observable effect today and implies a backwards-compat invariant the codebase doesn't uphold.

Sounds good and done! I didn't think about what could be implied (the backwards-compat invariant) by adding that attribute.

wmmc88 · 2026-05-08T17:12:25Z

+                .resolve
+                .as_ref()
+                .and_then(|resolve| resolve.nodes.iter().find(|node| node.id == *id))
+                .map_or_else(


This shouldn't be a warning. Two coherent options: (1) if wdk-sys missing from the build graph is invalid, return a ConfigError from from_env_auto() on None for wdk_sys_package_id so the build fails fast instead of silently omitting feature-gated linker args; (2) if it's a valid state, drop the warning entirely.

(2) is the right call. wdk-build can legitimately be consumed without wdk-sys -- for example, a crate that only wants the cfg plumbing it emits (driver_model__driver_type, driver_model__kmdf_version_major, etc.) without pulling in the FFI bindings (think a higher-level safe wrapper that re-exports from a separately-versioned wdk-sys, or a utility crate that just gates code on driver type). In that case enabled_api_subsets correctly should be empty and from_env_auto() should succeed silently -- the warning is flagging a valid usage pattern as if it were broken.

That makes sense, we now use expect to panic in case of a true build error.

…, changed enabled_api_subsets type to a BTreeSet, updated tests

Copilot

Pull request overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated 4 comments.

    cpu_architecture: CpuArchitecture,
    /// Build configuration of driver
    pub driver_config: DriverConfig,
+    /// List of features enabled for `wdk-sys` in resolved dependency graph


+                // Link against VhfKm.lib (Virtual HID Framework, kernel-mode) when
+                // the "hid" feature is enabled in wdk-sys. Required by drivers that
+                // create virtual HID devices.
+                if self.enabled_api_subsets.contains(&ApiSubset::Hid) {
+                    println!("cargo::rustc-cdylib-link-arg=VhfKm.lib");


+                // Link against VhfKm.lib (Virtual HID Framework, kernel-mode) when
+                // the "hid" feature is enabled in wdk-sys. Required by drivers that
+                // create virtual HID devices.
+                if self.enabled_api_subsets.contains(&ApiSubset::Hid) {
+                    println!("cargo::rustc-cdylib-link-arg=VhfKm.lib");


+                // Link against VhfUm.lib (Virtual HID Framework, user-mode) when
+                // the "hid" feature is enabled in wdk-sys. Required by drivers that
+                // create virtual HID devices.
+                if self.enabled_api_subsets.contains(&ApiSubset::Hid) {
+                    println!("cargo::rustc-cdylib-link-arg=VhfUm.lib");


Alan Ngo and others added 4 commits April 30, 2026 15:08

initial commit - add vhf lib link emission to wdk-build

294c27e

remove wdk-sys feature flag forward

b194380

add comments to linker emissions for vhf lib

cfae425

Merge branch 'microsoft:main' into vhf_lib_linker_args

70305e3

Alan632 self-assigned this May 1, 2026

Copilot AI review requested due to automatic review settings May 1, 2026 23:38

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Alan632 marked this pull request as ready for review May 4, 2026 17:47

wmmc88 requested changes May 4, 2026

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Comment thread crates/wdk-build/src/lib.rs Outdated

Alan Ngo added 2 commits May 5, 2026 21:50

redesigned wdk-build build script output linking vhf to use cargo met…

4427c85

…adata inspection (automatic) rather than crate features, removed vhf feature from Cargo.toml

formatting

7fc834a

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Comment thread crates/wdk-build/src/lib.rs Outdated

Comment thread crates/wdk-build/src/lib.rs Outdated

Comment thread crates/wdk-build/src/lib.rs Outdated

Comment thread crates/wdk-build/src/lib.rs

Comment thread crates/wdk-build/src/lib.rs Outdated

changed how the "hid" feature is checked in configure_binary_build

74ebe7c

wmmc88 requested changes May 6, 2026

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Comment thread crates/wdk-build/src/lib.rs Outdated

Comment thread crates/wdk-build/src/lib.rs Outdated

Comment thread crates/wdk-build/src/lib.rs Outdated

changed Config's enabled_api_subsets member to utilize the type safe …

6bdb8e3

…ApiSubset enum

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Alan Ngo added 2 commits May 6, 2026 21:27

added serde attribute to Config member for deserialize compatibility

8ff9e5b

extended config unit tests to include new member

0d8fe7f

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Comment thread crates/wdk-build/src/lib.rs Outdated

Comment thread crates/wdk-build/src/lib.rs Outdated

Comment thread crates/wdk-build/src/lib.rs Outdated

Comment thread crates/wdk-build/src/lib.rs Outdated

Comment thread crates/wdk-build/src/lib.rs Outdated

refactor api_subsets search to use match, refactor hid api check to u…

18d42f3

…se contains

wmmc88 requested changes May 8, 2026

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refactored feature filter to skip json and use ApiSubset deserializer…

55a63a1

…, changed enabled_api_subsets type to a BTreeSet, updated tests

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add error to panic message

d22d9db

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