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Diffstat (limited to 'rust/kernel/irq/request.rs')
| -rw-r--r-- | rust/kernel/irq/request.rs | 507 |
1 files changed, 507 insertions, 0 deletions
diff --git a/rust/kernel/irq/request.rs b/rust/kernel/irq/request.rs new file mode 100644 index 000000000000..b150563fdef8 --- /dev/null +++ b/rust/kernel/irq/request.rs @@ -0,0 +1,507 @@ +// SPDX-License-Identifier: GPL-2.0 +// SPDX-FileCopyrightText: Copyright 2025 Collabora ltd. + +//! This module provides types like [`Registration`] and +//! [`ThreadedRegistration`], which allow users to register handlers for a given +//! IRQ line. + +use core::marker::PhantomPinned; + +use crate::alloc::Allocator; +use crate::device::{Bound, Device}; +use crate::devres::Devres; +use crate::error::to_result; +use crate::irq::flags::Flags; +use crate::prelude::*; +use crate::str::CStr; +use crate::sync::Arc; + +/// The value that can be returned from a [`Handler`] or a [`ThreadedHandler`]. +#[repr(u32)] +pub enum IrqReturn { + /// The interrupt was not from this device or was not handled. + None = bindings::irqreturn_IRQ_NONE, + + /// The interrupt was handled by this device. + Handled = bindings::irqreturn_IRQ_HANDLED, +} + +/// Callbacks for an IRQ handler. +pub trait Handler: Sync { + /// The hard IRQ handler. + /// + /// This is executed in interrupt context, hence all corresponding + /// limitations do apply. + /// + /// All work that does not necessarily need to be executed from + /// interrupt context, should be deferred to a threaded handler. + /// See also [`ThreadedRegistration`]. + fn handle(&self, device: &Device<Bound>) -> IrqReturn; +} + +impl<T: ?Sized + Handler + Send> Handler for Arc<T> { + fn handle(&self, device: &Device<Bound>) -> IrqReturn { + T::handle(self, device) + } +} + +impl<T: ?Sized + Handler, A: Allocator> Handler for Box<T, A> { + fn handle(&self, device: &Device<Bound>) -> IrqReturn { + T::handle(self, device) + } +} + +/// # Invariants +/// +/// - `self.irq` is the same as the one passed to `request_{threaded}_irq`. +/// - `cookie` was passed to `request_{threaded}_irq` as the cookie. It is guaranteed to be unique +/// by the type system, since each call to `new` will return a different instance of +/// `Registration`. +#[pin_data(PinnedDrop)] +struct RegistrationInner { + irq: u32, + cookie: *mut c_void, +} + +impl RegistrationInner { + fn synchronize(&self) { + // SAFETY: safe as per the invariants of `RegistrationInner` + unsafe { bindings::synchronize_irq(self.irq) }; + } +} + +#[pinned_drop] +impl PinnedDrop for RegistrationInner { + fn drop(self: Pin<&mut Self>) { + // SAFETY: + // + // Safe as per the invariants of `RegistrationInner` and: + // + // - The containing struct is `!Unpin` and was initialized using + // pin-init, so it occupied the same memory location for the entirety of + // its lifetime. + // + // Notice that this will block until all handlers finish executing, + // i.e.: at no point will &self be invalid while the handler is running. + unsafe { bindings::free_irq(self.irq, self.cookie) }; + } +} + +// SAFETY: We only use `inner` on drop, which called at most once with no +// concurrent access. +unsafe impl Sync for RegistrationInner {} + +// SAFETY: It is safe to send `RegistrationInner` across threads. +unsafe impl Send for RegistrationInner {} + +/// A request for an IRQ line for a given device. +/// +/// # Invariants +/// +/// - `ìrq` is the number of an interrupt source of `dev`. +/// - `irq` has not been registered yet. +pub struct IrqRequest<'a> { + dev: &'a Device<Bound>, + irq: u32, +} + +impl<'a> IrqRequest<'a> { + /// Creates a new IRQ request for the given device and IRQ number. + /// + /// # Safety + /// + /// - `irq` should be a valid IRQ number for `dev`. + pub(crate) unsafe fn new(dev: &'a Device<Bound>, irq: u32) -> Self { + // INVARIANT: `irq` is a valid IRQ number for `dev`. + IrqRequest { dev, irq } + } + + /// Returns the IRQ number of an [`IrqRequest`]. + pub fn irq(&self) -> u32 { + self.irq + } +} + +/// A registration of an IRQ handler for a given IRQ line. +/// +/// # Examples +/// +/// The following is an example of using `Registration`. It uses a +/// [`Completion`] to coordinate between the IRQ +/// handler and process context. [`Completion`] uses interior mutability, so the +/// handler can signal with [`Completion::complete_all()`] and the process +/// context can wait with [`Completion::wait_for_completion()`] even though +/// there is no way to get a mutable reference to the any of the fields in +/// `Data`. +/// +/// [`Completion`]: kernel::sync::Completion +/// [`Completion::complete_all()`]: kernel::sync::Completion::complete_all +/// [`Completion::wait_for_completion()`]: kernel::sync::Completion::wait_for_completion +/// +/// ``` +/// use kernel::c_str; +/// use kernel::device::{Bound, Device}; +/// use kernel::irq::{self, Flags, IrqRequest, IrqReturn, Registration}; +/// use kernel::prelude::*; +/// use kernel::sync::{Arc, Completion}; +/// +/// // Data shared between process and IRQ context. +/// #[pin_data] +/// struct Data { +/// #[pin] +/// completion: Completion, +/// } +/// +/// impl irq::Handler for Data { +/// // Executed in IRQ context. +/// fn handle(&self, _dev: &Device<Bound>) -> IrqReturn { +/// self.completion.complete_all(); +/// IrqReturn::Handled +/// } +/// } +/// +/// // Registers an IRQ handler for the given IrqRequest. +/// // +/// // This runs in process context and assumes `request` was previously acquired from a device. +/// fn register_irq( +/// handler: impl PinInit<Data, Error>, +/// request: IrqRequest<'_>, +/// ) -> Result<Arc<Registration<Data>>> { +/// let registration = Registration::new(request, Flags::SHARED, c_str!("my_device"), handler); +/// +/// let registration = Arc::pin_init(registration, GFP_KERNEL)?; +/// +/// registration.handler().completion.wait_for_completion(); +/// +/// Ok(registration) +/// } +/// # Ok::<(), Error>(()) +/// ``` +/// +/// # Invariants +/// +/// * We own an irq handler whose cookie is a pointer to `Self`. +#[pin_data] +pub struct Registration<T: Handler + 'static> { + #[pin] + inner: Devres<RegistrationInner>, + + #[pin] + handler: T, + + /// Pinned because we need address stability so that we can pass a pointer + /// to the callback. + #[pin] + _pin: PhantomPinned, +} + +impl<T: Handler + 'static> Registration<T> { + /// Registers the IRQ handler with the system for the given IRQ number. + pub fn new<'a>( + request: IrqRequest<'a>, + flags: Flags, + name: &'static CStr, + handler: impl PinInit<T, Error> + 'a, + ) -> impl PinInit<Self, Error> + 'a { + try_pin_init!(&this in Self { + handler <- handler, + inner <- Devres::new( + request.dev, + try_pin_init!(RegistrationInner { + // INVARIANT: `this` is a valid pointer to the `Registration` instance + cookie: this.as_ptr().cast::<c_void>(), + irq: { + // SAFETY: + // - The callbacks are valid for use with request_irq. + // - If this succeeds, the slot is guaranteed to be valid until the + // destructor of Self runs, which will deregister the callbacks + // before the memory location becomes invalid. + // - When request_irq is called, everything that handle_irq_callback will + // touch has already been initialized, so it's safe for the callback to + // be called immediately. + to_result(unsafe { + bindings::request_irq( + request.irq, + Some(handle_irq_callback::<T>), + flags.into_inner(), + name.as_char_ptr(), + this.as_ptr().cast::<c_void>(), + ) + })?; + request.irq + } + }) + ), + _pin: PhantomPinned, + }) + } + + /// Returns a reference to the handler that was registered with the system. + pub fn handler(&self) -> &T { + &self.handler + } + + /// Wait for pending IRQ handlers on other CPUs. + /// + /// This will attempt to access the inner [`Devres`] container. + pub fn try_synchronize(&self) -> Result { + let inner = self.inner.try_access().ok_or(ENODEV)?; + inner.synchronize(); + Ok(()) + } + + /// Wait for pending IRQ handlers on other CPUs. + pub fn synchronize(&self, dev: &Device<Bound>) -> Result { + let inner = self.inner.access(dev)?; + inner.synchronize(); + Ok(()) + } +} + +/// # Safety +/// +/// This function should be only used as the callback in `request_irq`. +unsafe extern "C" fn handle_irq_callback<T: Handler>(_irq: i32, ptr: *mut c_void) -> c_uint { + // SAFETY: `ptr` is a pointer to `Registration<T>` set in `Registration::new` + let registration = unsafe { &*(ptr as *const Registration<T>) }; + // SAFETY: The irq callback is removed before the device is unbound, so the fact that the irq + // callback is running implies that the device has not yet been unbound. + let device = unsafe { registration.inner.device().as_bound() }; + + T::handle(®istration.handler, device) as c_uint +} + +/// The value that can be returned from [`ThreadedHandler::handle`]. +#[repr(u32)] +pub enum ThreadedIrqReturn { + /// The interrupt was not from this device or was not handled. + None = bindings::irqreturn_IRQ_NONE, + + /// The interrupt was handled by this device. + Handled = bindings::irqreturn_IRQ_HANDLED, + + /// The handler wants the handler thread to wake up. + WakeThread = bindings::irqreturn_IRQ_WAKE_THREAD, +} + +/// Callbacks for a threaded IRQ handler. +pub trait ThreadedHandler: Sync { + /// The hard IRQ handler. + /// + /// This is executed in interrupt context, hence all corresponding + /// limitations do apply. All work that does not necessarily need to be + /// executed from interrupt context, should be deferred to the threaded + /// handler, i.e. [`ThreadedHandler::handle_threaded`]. + /// + /// The default implementation returns [`ThreadedIrqReturn::WakeThread`]. + #[expect(unused_variables)] + fn handle(&self, device: &Device<Bound>) -> ThreadedIrqReturn { + ThreadedIrqReturn::WakeThread + } + + /// The threaded IRQ handler. + /// + /// This is executed in process context. The kernel creates a dedicated + /// `kthread` for this purpose. + fn handle_threaded(&self, device: &Device<Bound>) -> IrqReturn; +} + +impl<T: ?Sized + ThreadedHandler + Send> ThreadedHandler for Arc<T> { + fn handle(&self, device: &Device<Bound>) -> ThreadedIrqReturn { + T::handle(self, device) + } + + fn handle_threaded(&self, device: &Device<Bound>) -> IrqReturn { + T::handle_threaded(self, device) + } +} + +impl<T: ?Sized + ThreadedHandler, A: Allocator> ThreadedHandler for Box<T, A> { + fn handle(&self, device: &Device<Bound>) -> ThreadedIrqReturn { + T::handle(self, device) + } + + fn handle_threaded(&self, device: &Device<Bound>) -> IrqReturn { + T::handle_threaded(self, device) + } +} + +/// A registration of a threaded IRQ handler for a given IRQ line. +/// +/// Two callbacks are required: one to handle the IRQ, and one to handle any +/// other work in a separate thread. +/// +/// The thread handler is only called if the IRQ handler returns +/// [`ThreadedIrqReturn::WakeThread`]. +/// +/// # Examples +/// +/// The following is an example of using [`ThreadedRegistration`]. It uses a +/// [`Mutex`](kernel::sync::Mutex) to provide interior mutability. +/// +/// ``` +/// use kernel::c_str; +/// use kernel::device::{Bound, Device}; +/// use kernel::irq::{ +/// self, Flags, IrqRequest, IrqReturn, ThreadedHandler, ThreadedIrqReturn, +/// ThreadedRegistration, +/// }; +/// use kernel::prelude::*; +/// use kernel::sync::{Arc, Mutex}; +/// +/// // Declare a struct that will be passed in when the interrupt fires. The u32 +/// // merely serves as an example of some internal data. +/// // +/// // [`irq::ThreadedHandler::handle`] takes `&self`. This example +/// // illustrates how interior mutability can be used when sharing the data +/// // between process context and IRQ context. +/// #[pin_data] +/// struct Data { +/// #[pin] +/// value: Mutex<u32>, +/// } +/// +/// impl ThreadedHandler for Data { +/// // This will run (in a separate kthread) if and only if +/// // [`ThreadedHandler::handle`] returns [`WakeThread`], which it does by +/// // default. +/// fn handle_threaded(&self, _dev: &Device<Bound>) -> IrqReturn { +/// let mut data = self.value.lock(); +/// *data += 1; +/// IrqReturn::Handled +/// } +/// } +/// +/// // Registers a threaded IRQ handler for the given [`IrqRequest`]. +/// // +/// // This is executing in process context and assumes that `request` was +/// // previously acquired from a device. +/// fn register_threaded_irq( +/// handler: impl PinInit<Data, Error>, +/// request: IrqRequest<'_>, +/// ) -> Result<Arc<ThreadedRegistration<Data>>> { +/// let registration = +/// ThreadedRegistration::new(request, Flags::SHARED, c_str!("my_device"), handler); +/// +/// let registration = Arc::pin_init(registration, GFP_KERNEL)?; +/// +/// { +/// // The data can be accessed from process context too. +/// let mut data = registration.handler().value.lock(); +/// *data += 1; +/// } +/// +/// Ok(registration) +/// } +/// # Ok::<(), Error>(()) +/// ``` +/// +/// # Invariants +/// +/// * We own an irq handler whose cookie is a pointer to `Self`. +#[pin_data] +pub struct ThreadedRegistration<T: ThreadedHandler + 'static> { + #[pin] + inner: Devres<RegistrationInner>, + + #[pin] + handler: T, + + /// Pinned because we need address stability so that we can pass a pointer + /// to the callback. + #[pin] + _pin: PhantomPinned, +} + +impl<T: ThreadedHandler + 'static> ThreadedRegistration<T> { + /// Registers the IRQ handler with the system for the given IRQ number. + pub fn new<'a>( + request: IrqRequest<'a>, + flags: Flags, + name: &'static CStr, + handler: impl PinInit<T, Error> + 'a, + ) -> impl PinInit<Self, Error> + 'a { + try_pin_init!(&this in Self { + handler <- handler, + inner <- Devres::new( + request.dev, + try_pin_init!(RegistrationInner { + // INVARIANT: `this` is a valid pointer to the `ThreadedRegistration` instance. + cookie: this.as_ptr().cast::<c_void>(), + irq: { + // SAFETY: + // - The callbacks are valid for use with request_threaded_irq. + // - If this succeeds, the slot is guaranteed to be valid until the + // destructor of Self runs, which will deregister the callbacks + // before the memory location becomes invalid. + // - When request_threaded_irq is called, everything that the two callbacks + // will touch has already been initialized, so it's safe for the + // callbacks to be called immediately. + to_result(unsafe { + bindings::request_threaded_irq( + request.irq, + Some(handle_threaded_irq_callback::<T>), + Some(thread_fn_callback::<T>), + flags.into_inner(), + name.as_char_ptr(), + this.as_ptr().cast::<c_void>(), + ) + })?; + request.irq + } + }) + ), + _pin: PhantomPinned, + }) + } + + /// Returns a reference to the handler that was registered with the system. + pub fn handler(&self) -> &T { + &self.handler + } + + /// Wait for pending IRQ handlers on other CPUs. + /// + /// This will attempt to access the inner [`Devres`] container. + pub fn try_synchronize(&self) -> Result { + let inner = self.inner.try_access().ok_or(ENODEV)?; + inner.synchronize(); + Ok(()) + } + + /// Wait for pending IRQ handlers on other CPUs. + pub fn synchronize(&self, dev: &Device<Bound>) -> Result { + let inner = self.inner.access(dev)?; + inner.synchronize(); + Ok(()) + } +} + +/// # Safety +/// +/// This function should be only used as the callback in `request_threaded_irq`. +unsafe extern "C" fn handle_threaded_irq_callback<T: ThreadedHandler>( + _irq: i32, + ptr: *mut c_void, +) -> c_uint { + // SAFETY: `ptr` is a pointer to `ThreadedRegistration<T>` set in `ThreadedRegistration::new` + let registration = unsafe { &*(ptr as *const ThreadedRegistration<T>) }; + // SAFETY: The irq callback is removed before the device is unbound, so the fact that the irq + // callback is running implies that the device has not yet been unbound. + let device = unsafe { registration.inner.device().as_bound() }; + + T::handle(®istration.handler, device) as c_uint +} + +/// # Safety +/// +/// This function should be only used as the callback in `request_threaded_irq`. +unsafe extern "C" fn thread_fn_callback<T: ThreadedHandler>(_irq: i32, ptr: *mut c_void) -> c_uint { + // SAFETY: `ptr` is a pointer to `ThreadedRegistration<T>` set in `ThreadedRegistration::new` + let registration = unsafe { &*(ptr as *const ThreadedRegistration<T>) }; + // SAFETY: The irq callback is removed before the device is unbound, so the fact that the irq + // callback is running implies that the device has not yet been unbound. + let device = unsafe { registration.inner.device().as_bound() }; + + T::handle_threaded(®istration.handler, device) as c_uint +} |