Generalize Registration<T> to Registration<F: ForLt> and Device::registration_data<F: ForLt>() to return Pin<&F::Of<'_>>.
The stored 'static lifetime is shortened to the borrow lifetime of &self via ForLt::cast_ref; ForLt's covariance guarantee makes this sound. Signed-off-by: Danilo Krummrich <[email protected]> --- drivers/gpu/nova-core/driver.rs | 4 +- rust/kernel/auxiliary.rs | 67 +++++++++++++++++---------- samples/rust/rust_driver_auxiliary.rs | 7 +-- 3 files changed, 50 insertions(+), 28 deletions(-) diff --git a/drivers/gpu/nova-core/driver.rs b/drivers/gpu/nova-core/driver.rs index d0ccfbc8d0ea..ed154cd93fa8 100644 --- a/drivers/gpu/nova-core/driver.rs +++ b/drivers/gpu/nova-core/driver.rs @@ -21,6 +21,7 @@ }, Arc, }, + types::ForLt, }; use crate::gpu::Gpu; @@ -32,7 +33,8 @@ pub(crate) struct NovaCore { #[pin] pub(crate) gpu: Gpu, - _reg: Devres<auxiliary::Registration<()>>, + #[allow(clippy::type_complexity)] + _reg: Devres<auxiliary::Registration<ForLt!(())>>, } const BAR0_SIZE: usize = SZ_16M; diff --git a/rust/kernel/auxiliary.rs b/rust/kernel/auxiliary.rs index d2785a841380..cbfb32298fde 100644 --- a/rust/kernel/auxiliary.rs +++ b/rust/kernel/auxiliary.rs @@ -288,12 +288,16 @@ pub fn parent(&self) -> &device::Device<device::Bound> { /// Returns a pinned reference to the registration data set by the registering (parent) driver. /// - /// Returns [`EINVAL`] if `T` does not match the type used by the parent driver when calling + /// `F` is the [`ForLt`](trait@ForLt) encoding of the data type. The returned + /// reference has its lifetime shortened from `'static` to `&self`'s borrow lifetime via + /// [`ForLt::cast_ref`]. + /// + /// Returns [`EINVAL`] if `F` does not match the type used by the parent driver when calling /// [`Registration::new()`]. /// /// Returns [`ENOENT`] if no registration data has been set, e.g. when the device was /// registered by a C driver. - pub fn registration_data<T: 'static>(&self) -> Result<Pin<&T>> { + pub fn registration_data<F: ForLt>(&self) -> Result<Pin<&F::Of<'_>>> { // SAFETY: By the type invariant, `self.as_raw()` is a valid `struct auxiliary_device`. let ptr = unsafe { (*self.as_raw()).registration_data_rust }; if ptr.is_null() { @@ -306,18 +310,23 @@ pub fn registration_data<T: 'static>(&self) -> Result<Pin<&T>> { // SAFETY: `ptr` is non-null and was set via `into_foreign()` in `Registration::new()`; // `RegistrationData` is `#[repr(C)]` with `type_id` at offset 0, so reading a `TypeId` - // at the start of the allocation is valid regardless of `T`. + // at the start of the allocation is valid regardless of `F`. let type_id = unsafe { ptr.cast::<TypeId>().read() }; - if type_id != TypeId::of::<T>() { + if type_id != TypeId::of::<F::Of<'static>>() { return Err(EINVAL); } - // SAFETY: The `TypeId` check above confirms that the stored type is `T`; `ptr` remains - // valid until `Registration::drop()` calls `from_foreign()`. - let wrapper = unsafe { Pin::<KBox<RegistrationData<T>>>::borrow(ptr) }; + // SAFETY: The `TypeId` check above confirms that the stored type matches + // `F::Of<'static>`; `ptr` remains valid until `Registration::drop()` calls + // `from_foreign()`. + let wrapper = unsafe { Pin::<KBox<RegistrationData<F::Of<'static>>>>::borrow(ptr) }; // SAFETY: `data` is a structurally pinned field of `RegistrationData`. - Ok(unsafe { wrapper.map_unchecked(|w| &w.data) }) + let pinned: Pin<&F::Of<'static>> = unsafe { wrapper.map_unchecked(|w| &w.data) }; + + // SAFETY: The data was pinned when stored; `cast_ref` only shortens + // the lifetime, so the pinning guarantee is preserved. + Ok(unsafe { Pin::new_unchecked(F::cast_ref(pinned.get_ref())) }) } } @@ -406,43 +415,51 @@ struct RegistrationData<T> { /// This type represents the registration of a [`struct auxiliary_device`]. When its parent device /// is unbound, the corresponding auxiliary device will be unregistered from the system. /// -/// The type parameter `T` is the type of the registration data owned by the registering (parent) -/// driver. It can be accessed by the auxiliary driver through -/// [`Device::registration_data()`]. +/// The type parameter `F` is a [`ForLt`](trait@ForLt) encoding of the registration +/// data type. For non-lifetime-parameterized types, use [`ForLt!(T)`](macro@ForLt). +/// The data can be accessed by the auxiliary driver through [`Device::registration_data()`]. /// /// # Invariants /// /// `self.adev` always holds a valid pointer to an initialized and registered /// [`struct auxiliary_device`] whose `registration_data_rust` field points to a -/// valid `Pin<KBox<RegistrationData<T>>>`. -pub struct Registration<T: 'static> { +/// valid `Pin<KBox<RegistrationData<F::Of<'static>>>>`. +pub struct Registration<F: ForLt> { adev: NonNull<bindings::auxiliary_device>, - _data: PhantomData<T>, + _data: PhantomData<F>, } -impl<T: Send + Sync + 'static> Registration<T> { +impl<F: ForLt> Registration<F> +where + for<'a> F::Of<'a>: Send, +{ /// Create and register a new auxiliary device with the given registration data. /// /// The `data` is owned by the registration and can be accessed through the auxiliary device /// via [`Device::registration_data()`]. - pub fn new<E>( - parent: &device::Device<device::Bound>, + pub fn new<'bound, E>( + parent: &'bound device::Device<device::Bound>, name: &CStr, id: u32, modname: &CStr, - data: impl PinInit<T, E>, + data: impl PinInit<F::Of<'bound>, E>, ) -> Result<Devres<Self>> where Error: From<E>, { let data = KBox::pin_init::<Error>( try_pin_init!(RegistrationData { - type_id: TypeId::of::<T>(), + type_id: TypeId::of::<F::Of<'static>>(), data <- data, }), GFP_KERNEL, )?; + // SAFETY: Lifetimes are erased and do not affect layout, so RegistrationData<F::Of<'bound>> + // and RegistrationData<F::Of<'static>> have identical representation. + let data: Pin<KBox<RegistrationData<F::Of<'static>>>> = + unsafe { core::mem::transmute(data) }; + let boxed: KBox<Opaque<bindings::auxiliary_device>> = KBox::zeroed(GFP_KERNEL)?; let adev = boxed.get(); @@ -472,7 +489,9 @@ pub fn new<E>( if ret != 0 { // SAFETY: `registration_data` was set above via `into_foreign()`. drop(unsafe { - Pin::<KBox<RegistrationData<T>>>::from_foreign((*adev).registration_data_rust) + Pin::<KBox<RegistrationData<F::Of<'static>>>>::from_foreign( + (*adev).registration_data_rust, + ) }); // SAFETY: `adev` is guaranteed to be a valid pointer to a @@ -495,7 +514,7 @@ pub fn new<E>( } } -impl<T: 'static> Drop for Registration<T> { +impl<F: ForLt> Drop for Registration<F> { fn drop(&mut self) { // SAFETY: By the type invariant of `Self`, `self.adev.as_ptr()` is a valid registered // `struct auxiliary_device`. @@ -503,7 +522,7 @@ fn drop(&mut self) { // SAFETY: `registration_data` was set in `new()` via `into_foreign()`. drop(unsafe { - Pin::<KBox<RegistrationData<T>>>::from_foreign( + Pin::<KBox<RegistrationData<F::Of<'static>>>>::from_foreign( (*self.adev.as_ptr()).registration_data_rust, ) }); @@ -517,7 +536,7 @@ fn drop(&mut self) { } // SAFETY: A `Registration` of a `struct auxiliary_device` can be released from any thread. -unsafe impl<T: Send + Sync> Send for Registration<T> {} +unsafe impl<F: ForLt> Send for Registration<F> where for<'a> F::Of<'a>: Send {} // SAFETY: `Registration` does not expose any methods or fields that need synchronization. -unsafe impl<T: Send + Sync> Sync for Registration<T> {} +unsafe impl<F: ForLt> Sync for Registration<F> where for<'a> F::Of<'a>: Send {} diff --git a/samples/rust/rust_driver_auxiliary.rs b/samples/rust/rust_driver_auxiliary.rs index 6baeb1dde5da..de44ba901967 100644 --- a/samples/rust/rust_driver_auxiliary.rs +++ b/samples/rust/rust_driver_auxiliary.rs @@ -55,9 +55,10 @@ struct Data { index: u32, } +#[allow(clippy::type_complexity)] struct ParentDriver { - _reg0: Devres<auxiliary::Registration<Data>>, - _reg1: Devres<auxiliary::Registration<Data>>, + _reg0: Devres<auxiliary::Registration<ForLt!(Data)>>, + _reg1: Devres<auxiliary::Registration<ForLt!(Data)>>, } kernel::pci_device_table!( @@ -100,7 +101,7 @@ fn connect(adev: &auxiliary::Device<Bound>) -> Result { let dev = adev.parent(); let pdev: &pci::Device<Bound> = dev.try_into()?; - let data = adev.registration_data::<Data>()?; + let data = adev.registration_data::<ForLt!(Data)>()?; dev_info!( dev, -- 2.54.0
