[PATCH 16/24] rust: usb: make Driver trait lifetime-parameterized

Danilo Krummrich
2026-04-27T22:13:49Z

Make usb::Driver take a lifetime parameter 'a that ties device resources
to the binding scope.

Internally, Adapter<T: Driver> becomes Adapter<F: ForLt> with a bound
for<'a> F::Of<'a>: Driver<'a>; module_usb_driver! wraps the driver type
in ForLt!() so drivers don't have to.

Signed-off-by: Danilo Krummrich <dakr@kernel.org>
---
rust/kernel/usb.rs | 84 ++++++++++++++++++++-------------
samples/rust/rust_driver_usb.rs | 14 +++---
2 files changed, 58 insertions(+), 40 deletions(-)

diff --git a/rust/kernel/usb.rs b/rust/kernel/usb.rs
index 442e456fd2d3..f519444cf8d0 100644
--- a/rust/kernel/usb.rs
+++ b/rust/kernel/usb.rs
@@ -35,22 +35,34 @@
};

/// An adapter for the registration of USB drivers.
-pub struct Adapter<T: Driver>(T);
+///
+/// `F` is a [`ForLt`](trait@ForLt) type that maps lifetimes to the driver's device
+/// private data type, i.e. `F::Of<'a>` is the driver struct parameterized by `'a`. The macro
+/// `module_usb_driver!` generates this automatically via `ForLt!()`.
+pub struct Adapter<F>(PhantomData<F>);

// SAFETY:
// - `bindings::usb_driver` is a C type declared as `repr(C)`.
-// - `T` is the type of the driver's device private data.
+// - `F::Of<'static>` is the stored type of the driver's device private data.
// - `struct usb_driver` embeds a `struct device_driver`.
// - `DEVICE_DRIVER_OFFSET` is the correct byte offset to the embedded `struct device_driver`.
-unsafe impl<T: Driver + 'static> driver::DriverLayout for Adapter<T> {
+unsafe impl<F> driver::DriverLayout for Adapter<F>
+where
+ F: ForLt + 'static,
+ for<'a> F::Of<'a>: Driver<'a>,
+{
type DriverType = bindings::usb_driver;
- type DriverData = ForLt!(T);
+ type DriverData = F;
const DEVICE_DRIVER_OFFSET: usize = core::mem::offset_of!(Self::DriverType, driver);
}

// SAFETY: A call to `unregister` for a given instance of `DriverType` is guaranteed to be valid if
// a preceding call to `register` has been successful.
-unsafe impl<T: Driver + 'static> driver::RegistrationOps for Adapter<T> {
+unsafe impl<F> driver::RegistrationOps for Adapter<F>
+where
+ F: ForLt + 'static,
+ for<'a> F::Of<'a>: Driver<'a>,
+{
unsafe fn register(
udrv: &Opaque<Self::DriverType>,
name: &'static CStr,
@@ -61,7 +73,7 @@ unsafe fn register(
(*udrv.get()).name = name.as_char_ptr();
(*udrv.get()).probe = Some(Self::probe_callback);
(*udrv.get()).disconnect = Some(Self::disconnect_callback);
- (*udrv.get()).id_table = T::ID_TABLE.as_ptr();
+ (*udrv.get()).id_table = <F::Of<'static> as Driver<'static>>::ID_TABLE.as_ptr();
}

// SAFETY: `udrv` is guaranteed to be a valid `DriverType`.
@@ -76,7 +88,11 @@ unsafe fn unregister(udrv: &Opaque<Self::DriverType>) {
}
}

-impl<T: Driver + 'static> Adapter<T> {
+impl<F> Adapter<F>
+where
+ F: ForLt + 'static,
+ for<'a> F::Of<'a>: Driver<'a>,
+{
extern "C" fn probe_callback(
intf: *mut bindings::usb_interface,
id: *const bindings::usb_device_id,
@@ -87,16 +103,16 @@ extern "C" fn probe_callback(
// INVARIANT: `intf` is valid for the duration of `probe_callback()`.
let intf = unsafe { &*intf.cast::<Interface<device::CoreInternal>>() };

- from_result(|| {
- // SAFETY: `DeviceId` is a `#[repr(transparent)]` wrapper of `struct usb_device_id` and
- // does not add additional invariants, so it's safe to transmute.
- let id = unsafe { &*id.cast::<DeviceId>() };
+ // SAFETY: `DeviceId` is a `#[repr(transparent)]` wrapper of `struct usb_device_id` and
+ // does not add additional invariants, so it's safe to transmute.
+ let id = unsafe { &*id.cast::<DeviceId>() };

- let info = T::ID_TABLE.info(id.index());
- let data = T::probe(intf, id, info);
+ from_result(|| {
+ let info = <F::Of<'_> as Driver<'_>>::ID_TABLE.info(id.index());
+ let data = <F::Of<'_> as Driver<'_>>::probe(intf, id, info);

let dev: &device::Device<device::CoreInternal> = intf.as_ref();
- dev.set_drvdata::<ForLt!(T)>(data)?;
+ dev.set_drvdata::<F>(data)?;
Ok(0)
})
}
@@ -111,11 +127,10 @@ extern "C" fn disconnect_callback(intf: *mut bindings::usb_interface) {
let dev: &device::Device<device::CoreInternal> = intf.as_ref();

// SAFETY: `disconnect_callback` is only ever called after a successful call to
- // `probe_callback`, hence it's guaranteed that `Device::set_drvdata()` has been called
- // and stored a `Pin<KBox<T>>`.
- let data = unsafe { dev.drvdata_borrow::<ForLt!(T)>() };
+ // `probe_callback`, hence it's guaranteed that drvdata has been set.
+ let data = unsafe { dev.drvdata_borrow::<F>() };

- T::disconnect(intf, data);
+ <F::Of<'_> as Driver<'_>>::disconnect(intf, data);
}
}

@@ -281,29 +296,29 @@ macro_rules! usb_device_table {
/// kernel::usb_device_table!(
/// USB_TABLE,
/// MODULE_USB_TABLE,
-/// <MyDriver as usb::Driver>::IdInfo,
+/// <MyDriver as usb::Driver<'_>>::IdInfo,
/// [
/// (usb::DeviceId::from_id(0x1234, 0x5678), ()),
/// (usb::DeviceId::from_id(0xabcd, 0xef01), ()),
/// ]
/// );
///
-/// impl usb::Driver for MyDriver {
+/// impl<'a> usb::Driver<'a> for MyDriver {
/// type IdInfo = ();
/// const ID_TABLE: usb::IdTable<Self::IdInfo> = &USB_TABLE;
///
/// fn probe(
-/// _interface: &usb::Interface<Core>,
-/// _id: &usb::DeviceId,
-/// _info: &Self::IdInfo,
-/// ) -> impl PinInit<Self, Error> {
+/// _interface: &'a usb::Interface<Core>,
+/// _id: &'a usb::DeviceId,
+/// _info: &'a Self::IdInfo,
+/// ) -> impl PinInit<Self, Error> + 'a {
/// Err(ENODEV)
/// }
///
-/// fn disconnect(_interface: &usb::Interface<Core>, _data: Pin<&Self>) {}
+/// fn disconnect(_interface: &'a usb::Interface<Core>, _data: Pin<&'a Self>) {}
/// }
///```
-pub trait Driver {
+pub trait Driver<'a> {
/// The type holding information about each one of the device ids supported by the driver.
type IdInfo: 'static;

@@ -315,15 +330,15 @@ pub trait Driver {
/// Called when a new USB interface is bound to this driver.
/// Implementers should attempt to initialize the interface here.
fn probe(
- interface: &Interface<device::Core>,
- id: &DeviceId,
- id_info: &Self::IdInfo,
- ) -> impl PinInit<Self, Error>;
+ interface: &'a Interface<device::Core>,
+ id: &'a DeviceId,
+ id_info: &'a Self::IdInfo,
+ ) -> impl PinInit<Self, Error> + 'a;

/// USB driver disconnect.
///
/// Called when the USB interface is about to be unbound from this driver.
- fn disconnect(interface: &Interface<device::Core>, data: Pin<&Self>);
+ fn disconnect(interface: &'a Interface<device::Core>, data: Pin<&'a Self>);
}

/// A USB interface.
@@ -486,7 +501,10 @@ unsafe impl Sync for Device<device::Bound> {}
/// ```
#[macro_export]
macro_rules! module_usb_driver {
- ($($f:tt)*) => {
- $crate::module_driver!(<T>, $crate::usb::Adapter<T>, { $($f)* });
+ (type: $type:ty, $($rest:tt)*) => {
+ $crate::module_driver!(<T>, $crate::usb::Adapter<T>, {
+ type: $crate::types::ForLt!($type),
+ $($rest)*
+ });
}
}
diff --git a/samples/rust/rust_driver_usb.rs b/samples/rust/rust_driver_usb.rs
index ab72e99e1274..6f3e5db9f35d 100644
--- a/samples/rust/rust_driver_usb.rs
+++ b/samples/rust/rust_driver_usb.rs
@@ -20,26 +20,26 @@ struct SampleDriver {
kernel::usb_device_table!(
USB_TABLE,
MODULE_USB_TABLE,
- <SampleDriver as usb::Driver>::IdInfo,
+ <SampleDriver as usb::Driver<'_>>::IdInfo,
[(usb::DeviceId::from_id(0x1234, 0x5678), ()),]
);

-impl usb::Driver for SampleDriver {
+impl<'a> usb::Driver<'a> for SampleDriver {
type IdInfo = ();
const ID_TABLE: usb::IdTable<Self::IdInfo> = &USB_TABLE;

fn probe(
- intf: &usb::Interface<Core>,
- _id: &usb::DeviceId,
- _info: &Self::IdInfo,
- ) -> impl PinInit<Self, Error> {
+ intf: &'a usb::Interface<Core>,
+ _id: &'a usb::DeviceId,
+ _info: &'a Self::IdInfo,
+ ) -> impl PinInit<Self, Error> + 'a {
let dev: &device::Device<Core> = intf.as_ref();
dev_info!(dev, "Rust USB driver sample probed\n");

Ok(Self { _intf: intf.into() })
}

- fn disconnect(intf: &usb::Interface<Core>, _data: Pin<&Self>) {
+ fn disconnect(intf: &'a usb::Interface<Core>, _data: Pin<&'a Self>) {
let dev: &device::Device<Core> = intf.as_ref();
dev_info!(dev, "Rust USB driver sample disconnected\n");
}
--
2.54.0