[PATCH v5 15/24] rust: usb: make Driver trait lifetime-parameterized

[Danilo Krummrich]

Add a 'bound lifetime to the associated Data, changing type Data to type
Data<'bound>.

This allows the driver's bus device private data to capture the device /
driver bound lifetime; device resources can be stored directly by
reference rather than requiring Devres.

The probe() and disconnect() callbacks thus gain a 'bound lifetime
parameter on the methods themselves; avoiding a global lifetime on the
trait impl.

Existing drivers set type Data<'bound> = Self, preserving the current
behavior.

Reviewed-by: Alexandre Courbot <acourbot@xxxxxxxxxx>
Reviewed-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Reviewed-by: Eliot Courtney <ecourtney@xxxxxxxxxx>
Signed-off-by: Danilo Krummrich <dakr@xxxxxxxxxx>
---
 rust/kernel/usb.rs              | 37 ++++++++++++++++++++-------------
 samples/rust/rust_driver_usb.rs | 12 +++++------
 2 files changed, 28 insertions(+), 21 deletions(-)

diff --git a/rust/kernel/usb.rs b/rust/kernel/usb.rs
index 1dbb8387b463..7aff0c82d0af 100644
--- a/rust/kernel/usb.rs
+++ b/rust/kernel/usb.rs
@@ -41,7 +41,7 @@
 // - `DEVICE_DRIVER_OFFSET` is the correct byte offset to the embedded `struct device_driver`.
 unsafe impl<T: Driver> driver::DriverLayout for Adapter<T> {
     type DriverType = bindings::usb_driver;
-    type DriverData<'bound> = T::Data;
+    type DriverData<'bound> = T::Data<'bound>;
     const DEVICE_DRIVER_OFFSET: usize = core::mem::offset_of!(Self::DriverType, driver);
 }
 
@@ -109,8 +109,8 @@ extern "C" fn disconnect_callback(intf: *mut bindings::usb_interface) {
 
         // 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::Data>>`.
-        let data = unsafe { dev.drvdata_borrow::<T::Data>() };
+        // and stored a `Pin<KBox<T::Data<'_>>>`.
+        let data = unsafe { dev.drvdata_borrow::<T::Data<'_>>() };
 
         T::disconnect(intf, data);
     }
@@ -287,18 +287,22 @@ macro_rules! usb_device_table {
 ///
 /// impl usb::Driver for MyDriver {
 ///     type IdInfo = ();
-///     type Data = Self;
+///     type Data<'bound> = Self;
 ///     const ID_TABLE: usb::IdTable<Self::IdInfo> = &USB_TABLE;
 ///
-///     fn probe(
-///         _interface: &usb::Interface<Core<'_>>,
+///     fn probe<'bound>(
+///         _interface: &'bound usb::Interface<Core<'_>>,
 ///         _id: &usb::DeviceId,
-///         _info: &Self::IdInfo,
-///     ) -> impl PinInit<Self::Data, Error> {
+///         _info: &'bound Self::IdInfo,
+///     ) -> impl PinInit<Self::Data<'bound>, Error> + 'bound {
 ///         Err(ENODEV)
 ///     }
 ///
-///     fn disconnect(_interface: &usb::Interface<Core<'_>>, _data: Pin<&Self::Data>) {}
+///     fn disconnect<'bound>(
+///         _interface: &'bound usb::Interface<Core<'_>>,
+///         _data: Pin<&Self::Data<'bound>>,
+///     ) {
+///     }
 /// }
 ///```
 pub trait Driver {
@@ -306,7 +310,7 @@ pub trait Driver {
     type IdInfo: 'static;
 
     /// The type of the driver's bus device private data.
-    type Data: Send;
+    type Data<'bound>: Send + 'bound;
 
     /// The table of device ids supported by the driver.
     const ID_TABLE: IdTable<Self::IdInfo>;
@@ -315,16 +319,19 @@ 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<'_>>,
+    fn probe<'bound>(
+        interface: &'bound Interface<device::Core<'_>>,
         id: &DeviceId,
-        id_info: &Self::IdInfo,
-    ) -> impl PinInit<Self::Data, Error>;
+        id_info: &'bound Self::IdInfo,
+    ) -> impl PinInit<Self::Data<'bound>, Error> + 'bound;
 
     /// 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::Data>);
+    fn disconnect<'bound>(
+        interface: &'bound Interface<device::Core<'_>>,
+        data: Pin<&Self::Data<'bound>>,
+    );
 }
 
 /// A USB interface.
diff --git a/samples/rust/rust_driver_usb.rs b/samples/rust/rust_driver_usb.rs
index e900993335e9..02bd5085f9bc 100644
--- a/samples/rust/rust_driver_usb.rs
+++ b/samples/rust/rust_driver_usb.rs
@@ -26,21 +26,21 @@ struct SampleDriver {
 
 impl usb::Driver for SampleDriver {
     type IdInfo = ();
-    type Data = Self;
+    type Data<'bound> = Self;
     const ID_TABLE: usb::IdTable<Self::IdInfo> = &USB_TABLE;
 
-    fn probe(
-        intf: &usb::Interface<Core<'_>>,
+    fn probe<'bound>(
+        intf: &'bound usb::Interface<Core<'_>>,
         _id: &usb::DeviceId,
-        _info: &Self::IdInfo,
-    ) -> impl PinInit<Self, Error> {
+        _info: &'bound Self::IdInfo,
+    ) -> impl PinInit<Self, Error> + 'bound {
         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<'bound>(intf: &'bound usb::Interface<Core<'_>>, _data: Pin<&Self>) {
         let dev: &device::Device<Core<'_>> = intf.as_ref();
         dev_info!(dev, "Rust USB driver sample disconnected\n");
     }
-- 
2.54.0