Adding upstream version 6.7.7.upstream/6.7.7

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

8 files changed, 739 insertions, 16 deletions

diff --git a/rust/kernel/init.rs b/rust/kernel/init.rs
index 4ebb6f23fc..65be9ae57b 100644
--- a/rust/kernel/init.rs
+++ b/rust/kernel/init.rs
@@ -35,7 +35,7 @@
 //! that you need to write `<-` instead of `:` for fields that you want to initialize in-place.
 //!
 //! ```rust
-//! # #![allow(clippy::disallowed_names, clippy::new_ret_no_self)]
+//! # #![allow(clippy::disallowed_names)]
 //! use kernel::{prelude::*, sync::Mutex, new_mutex};
 //! # use core::pin::Pin;
 //! #[pin_data]
@@ -55,7 +55,7 @@
 //! (or just the stack) to actually initialize a `Foo`:
 //!
 //! ```rust
-//! # #![allow(clippy::disallowed_names, clippy::new_ret_no_self)]
+//! # #![allow(clippy::disallowed_names)]
 //! # use kernel::{prelude::*, sync::Mutex, new_mutex};
 //! # use core::pin::Pin;
 //! # #[pin_data]
@@ -86,7 +86,7 @@
 //! To declare an init macro/function you just return an [`impl PinInit<T, E>`]:
 //!
 //! ```rust
-//! # #![allow(clippy::disallowed_names, clippy::new_ret_no_self)]
+//! # #![allow(clippy::disallowed_names)]
 //! # use kernel::{sync::Mutex, prelude::*, new_mutex, init::PinInit, try_pin_init};
 //! #[pin_data]
 //! struct DriverData {
@@ -236,7 +236,7 @@ pub mod macros;
 /// # Examples
 ///
 /// ```rust
-/// # #![allow(clippy::disallowed_names, clippy::new_ret_no_self)]
+/// # #![allow(clippy::disallowed_names)]
 /// # use kernel::{init, macros::pin_data, pin_init, stack_pin_init, init::*, sync::Mutex, new_mutex};
 /// # use core::pin::Pin;
 /// #[pin_data]
@@ -288,7 +288,7 @@ macro_rules! stack_pin_init {
 /// # Examples
 ///
 /// ```rust,ignore
-/// # #![allow(clippy::disallowed_names, clippy::new_ret_no_self)]
+/// # #![allow(clippy::disallowed_names)]
 /// # use kernel::{init, pin_init, stack_try_pin_init, init::*, sync::Mutex, new_mutex};
 /// # use macros::pin_data;
 /// # use core::{alloc::AllocError, pin::Pin};
@@ -314,7 +314,7 @@ macro_rules! stack_pin_init {
 /// ```
 ///
 /// ```rust,ignore
-/// # #![allow(clippy::disallowed_names, clippy::new_ret_no_self)]
+/// # #![allow(clippy::disallowed_names)]
 /// # use kernel::{init, pin_init, stack_try_pin_init, init::*, sync::Mutex, new_mutex};
 /// # use macros::pin_data;
 /// # use core::{alloc::AllocError, pin::Pin};
@@ -366,7 +366,7 @@ macro_rules! stack_try_pin_init {
 /// The syntax is almost identical to that of a normal `struct` initializer:
 ///
 /// ```rust
-/// # #![allow(clippy::disallowed_names, clippy::new_ret_no_self)]
+/// # #![allow(clippy::disallowed_names)]
 /// # use kernel::{init, pin_init, macros::pin_data, init::*};
 /// # use core::pin::Pin;
 /// #[pin_data]
@@ -411,7 +411,7 @@ macro_rules! stack_try_pin_init {
 /// To create an initializer function, simply declare it like this:
 ///
 /// ```rust
-/// # #![allow(clippy::disallowed_names, clippy::new_ret_no_self)]
+/// # #![allow(clippy::disallowed_names)]
 /// # use kernel::{init, pin_init, prelude::*, init::*};
 /// # use core::pin::Pin;
 /// # #[pin_data]
@@ -438,7 +438,7 @@ macro_rules! stack_try_pin_init {
 /// Users of `Foo` can now create it like this:
 ///
 /// ```rust
-/// # #![allow(clippy::disallowed_names, clippy::new_ret_no_self)]
+/// # #![allow(clippy::disallowed_names)]
 /// # use kernel::{init, pin_init, macros::pin_data, init::*};
 /// # use core::pin::Pin;
 /// # #[pin_data]
@@ -466,7 +466,7 @@ macro_rules! stack_try_pin_init {
 /// They can also easily embed it into their own `struct`s:
 ///
 /// ```rust
-/// # #![allow(clippy::disallowed_names, clippy::new_ret_no_self)]
+/// # #![allow(clippy::disallowed_names)]
 /// # use kernel::{init, pin_init, macros::pin_data, init::*};
 /// # use core::pin::Pin;
 /// # #[pin_data]
diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
index e881170023..e6aff80b52 100644
--- a/rust/kernel/lib.rs
+++ b/rust/kernel/lib.rs
@@ -16,6 +16,8 @@
 #![feature(coerce_unsized)]
 #![feature(dispatch_from_dyn)]
 #![feature(new_uninit)]
+#![feature(offset_of)]
+#![feature(ptr_metadata)]
 #![feature(receiver_trait)]
 #![feature(unsize)]
 
@@ -45,6 +47,7 @@ pub mod str;
 pub mod sync;
 pub mod task;
 pub mod types;
+pub mod workqueue;
 
 #[doc(hidden)]
 pub use bindings;
diff --git a/rust/kernel/print.rs b/rust/kernel/print.rs
index 8009184bf6..f48926e3e9 100644
--- a/rust/kernel/print.rs
+++ b/rust/kernel/print.rs
@@ -399,6 +399,7 @@ macro_rules! pr_debug (
 /// Mimics the interface of [`std::print!`]. See [`core::fmt`] and
 /// `alloc::format!` for information about the formatting syntax.
 ///
+/// [`pr_info!`]: crate::pr_info!
 /// [`pr_cont`]: https://www.kernel.org/doc/html/latest/core-api/printk-basics.html#c.pr_cont
 /// [`std::print!`]: https://doc.rust-lang.org/std/macro.print.html
 ///
diff --git a/rust/kernel/sync/arc.rs b/rust/kernel/sync/arc.rs
index 3d496391a9..77cdbcf7bd 100644
--- a/rust/kernel/sync/arc.rs
+++ b/rust/kernel/sync/arc.rs
@@ -24,13 +24,13 @@ use crate::{
 };
 use alloc::boxed::Box;
 use core::{
-    alloc::AllocError,
+    alloc::{AllocError, Layout},
     fmt,
     marker::{PhantomData, Unsize},
     mem::{ManuallyDrop, MaybeUninit},
     ops::{Deref, DerefMut},
     pin::Pin,
-    ptr::NonNull,
+    ptr::{NonNull, Pointee},
 };
 use macros::pin_data;
 
@@ -215,6 +215,48 @@ impl<T: ?Sized> Arc<T> {
         }
     }
 
+    /// Convert the [`Arc`] into a raw pointer.
+    ///
+    /// The raw pointer has ownership of the refcount that this Arc object owned.
+    pub fn into_raw(self) -> *const T {
+        let ptr = self.ptr.as_ptr();
+        core::mem::forget(self);
+        // SAFETY: The pointer is valid.
+        unsafe { core::ptr::addr_of!((*ptr).data) }
+    }
+
+    /// Recreates an [`Arc`] instance previously deconstructed via [`Arc::into_raw`].
+    ///
+    /// # Safety
+    ///
+    /// `ptr` must have been returned by a previous call to [`Arc::into_raw`]. Additionally, it
+    /// must not be called more than once for each previous call to [`Arc::into_raw`].
+    pub unsafe fn from_raw(ptr: *const T) -> Self {
+        let refcount_layout = Layout::new::<bindings::refcount_t>();
+        // SAFETY: The caller guarantees that the pointer is valid.
+        let val_layout = Layout::for_value(unsafe { &*ptr });
+        // SAFETY: We're computing the layout of a real struct that existed when compiling this
+        // binary, so its layout is not so large that it can trigger arithmetic overflow.
+        let val_offset = unsafe { refcount_layout.extend(val_layout).unwrap_unchecked().1 };
+
+        let metadata: <T as Pointee>::Metadata = core::ptr::metadata(ptr);
+        // SAFETY: The metadata of `T` and `ArcInner<T>` is the same because `ArcInner` is a struct
+        // with `T` as its last field.
+        //
+        // This is documented at:
+        // <https://doc.rust-lang.org/std/ptr/trait.Pointee.html>.
+        let metadata: <ArcInner<T> as Pointee>::Metadata =
+            unsafe { core::mem::transmute_copy(&metadata) };
+        // SAFETY: The pointer is in-bounds of an allocation both before and after offsetting the
+        // pointer, since it originates from a previous call to `Arc::into_raw` and is still valid.
+        let ptr = unsafe { (ptr as *mut u8).sub(val_offset) as *mut () };
+        let ptr = core::ptr::from_raw_parts_mut(ptr, metadata);
+
+        // SAFETY: By the safety requirements we know that `ptr` came from `Arc::into_raw`, so the
+        // reference count held then will be owned by the new `Arc` object.
+        unsafe { Self::from_inner(NonNull::new_unchecked(ptr)) }
+    }
+
     /// Returns an [`ArcBorrow`] from the given [`Arc`].
     ///
     /// This is useful when the argument of a function call is an [`ArcBorrow`] (e.g., in a method
@@ -302,7 +344,7 @@ impl<T: ?Sized> Drop for Arc<T> {
             // The count reached zero, we must free the memory.
             //
             // SAFETY: The pointer was initialised from the result of `Box::leak`.
-            unsafe { Box::from_raw(self.ptr.as_ptr()) };
+            unsafe { drop(Box::from_raw(self.ptr.as_ptr())) };
         }
     }
 }
diff --git a/rust/kernel/sync/condvar.rs b/rust/kernel/sync/condvar.rs
index ed353399c4..b679b6f6db 100644
--- a/rust/kernel/sync/condvar.rs
+++ b/rust/kernel/sync/condvar.rs
@@ -91,7 +91,6 @@ unsafe impl Sync for CondVar {}
 
 impl CondVar {
     /// Constructs a new condvar initialiser.
-    #[allow(clippy::new_ret_no_self)]
     pub fn new(name: &'static CStr, key: &'static LockClassKey) -> impl PinInit<Self> {
         pin_init!(Self {
             _pin: PhantomPinned,
diff --git a/rust/kernel/sync/lock.rs b/rust/kernel/sync/lock.rs
index 70a785f047..f12a684bc9 100644
--- a/rust/kernel/sync/lock.rs
+++ b/rust/kernel/sync/lock.rs
@@ -99,7 +99,6 @@ unsafe impl<T: ?Sized + Send, B: Backend> Sync for Lock<T, B> {}
 
 impl<T, B: Backend> Lock<T, B> {
     /// Constructs a new lock initialiser.
-    #[allow(clippy::new_ret_no_self)]
     pub fn new(t: T, name: &'static CStr, key: &'static LockClassKey) -> impl PinInit<Self> {
         pin_init!(Self {
             data: UnsafeCell::new(t),
diff --git a/rust/kernel/task.rs b/rust/kernel/task.rs
index 7eda15e5f1..b2299bc7ac 100644
--- a/rust/kernel/task.rs
+++ b/rust/kernel/task.rs
@@ -82,7 +82,7 @@ impl Task {
     /// Returns a task reference for the currently executing task/thread.
     ///
     /// The recommended way to get the current task/thread is to use the
-    /// [`current`](crate::current) macro because it is safe.
+    /// [`current`] macro because it is safe.
     ///
     /// # Safety
     ///
diff --git a/rust/kernel/workqueue.rs b/rust/kernel/workqueue.rs
new file mode 100644
index 0000000000..b67fb1ba16
--- /dev/null
+++ b/rust/kernel/workqueue.rs
@@ -0,0 +1,679 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Work queues.
+//!
+//! This file has two components: The raw work item API, and the safe work item API.
+//!
+//! One pattern that is used in both APIs is the `ID` const generic, which exists to allow a single
+//! type to define multiple `work_struct` fields. This is done by choosing an id for each field,
+//! and using that id to specify which field you wish to use. (The actual value doesn't matter, as
+//! long as you use different values for different fields of the same struct.) Since these IDs are
+//! generic, they are used only at compile-time, so they shouldn't exist in the final binary.
+//!
+//! # The raw API
+//!
+//! The raw API consists of the `RawWorkItem` trait, where the work item needs to provide an
+//! arbitrary function that knows how to enqueue the work item. It should usually not be used
+//! directly, but if you want to, you can use it without using the pieces from the safe API.
+//!
+//! # The safe API
+//!
+//! The safe API is used via the `Work` struct and `WorkItem` traits. Furthermore, it also includes
+//! a trait called `WorkItemPointer`, which is usually not used directly by the user.
+//!
+//!  * The `Work` struct is the Rust wrapper for the C `work_struct` type.
+//!  * The `WorkItem` trait is implemented for structs that can be enqueued to a workqueue.
+//!  * The `WorkItemPointer` trait is implemented for the pointer type that points at a something
+//!    that implements `WorkItem`.
+//!
+//! ## Example
+//!
+//! This example defines a struct that holds an integer and can be scheduled on the workqueue. When
+//! the struct is executed, it will print the integer. Since there is only one `work_struct` field,
+//! we do not need to specify ids for the fields.
+//!
+//! ```
+//! use kernel::prelude::*;
+//! use kernel::sync::Arc;
+//! use kernel::workqueue::{self, Work, WorkItem};
+//! use kernel::{impl_has_work, new_work};
+//!
+//! #[pin_data]
+//! struct MyStruct {
+//!     value: i32,
+//!     #[pin]
+//!     work: Work<MyStruct>,
+//! }
+//!
+//! impl_has_work! {
+//!     impl HasWork<Self> for MyStruct { self.work }
+//! }
+//!
+//! impl MyStruct {
+//!     fn new(value: i32) -> Result<Arc<Self>> {
+//!         Arc::pin_init(pin_init!(MyStruct {
+//!             value,
+//!             work <- new_work!("MyStruct::work"),
+//!         }))
+//!     }
+//! }
+//!
+//! impl WorkItem for MyStruct {
+//!     type Pointer = Arc<MyStruct>;
+//!
+//!     fn run(this: Arc<MyStruct>) {
+//!         pr_info!("The value is: {}", this.value);
+//!     }
+//! }
+//!
+//! /// This method will enqueue the struct for execution on the system workqueue, where its value
+//! /// will be printed.
+//! fn print_later(val: Arc<MyStruct>) {
+//!     let _ = workqueue::system().enqueue(val);
+//! }
+//! ```
+//!
+//! The following example shows how multiple `work_struct` fields can be used:
+//!
+//! ```
+//! use kernel::prelude::*;
+//! use kernel::sync::Arc;
+//! use kernel::workqueue::{self, Work, WorkItem};
+//! use kernel::{impl_has_work, new_work};
+//!
+//! #[pin_data]
+//! struct MyStruct {
+//!     value_1: i32,
+//!     value_2: i32,
+//!     #[pin]
+//!     work_1: Work<MyStruct, 1>,
+//!     #[pin]
+//!     work_2: Work<MyStruct, 2>,
+//! }
+//!
+//! impl_has_work! {
+//!     impl HasWork<Self, 1> for MyStruct { self.work_1 }
+//!     impl HasWork<Self, 2> for MyStruct { self.work_2 }
+//! }
+//!
+//! impl MyStruct {
+//!     fn new(value_1: i32, value_2: i32) -> Result<Arc<Self>> {
+//!         Arc::pin_init(pin_init!(MyStruct {
+//!             value_1,
+//!             value_2,
+//!             work_1 <- new_work!("MyStruct::work_1"),
+//!             work_2 <- new_work!("MyStruct::work_2"),
+//!         }))
+//!     }
+//! }
+//!
+//! impl WorkItem<1> for MyStruct {
+//!     type Pointer = Arc<MyStruct>;
+//!
+//!     fn run(this: Arc<MyStruct>) {
+//!         pr_info!("The value is: {}", this.value_1);
+//!     }
+//! }
+//!
+//! impl WorkItem<2> for MyStruct {
+//!     type Pointer = Arc<MyStruct>;
+//!
+//!     fn run(this: Arc<MyStruct>) {
+//!         pr_info!("The second value is: {}", this.value_2);
+//!     }
+//! }
+//!
+//! fn print_1_later(val: Arc<MyStruct>) {
+//!     let _ = workqueue::system().enqueue::<Arc<MyStruct>, 1>(val);
+//! }
+//!
+//! fn print_2_later(val: Arc<MyStruct>) {
+//!     let _ = workqueue::system().enqueue::<Arc<MyStruct>, 2>(val);
+//! }
+//! ```
+//!
+//! C header: [`include/linux/workqueue.h`](../../../../include/linux/workqueue.h)
+
+use crate::{bindings, prelude::*, sync::Arc, sync::LockClassKey, types::Opaque};
+use alloc::alloc::AllocError;
+use alloc::boxed::Box;
+use core::marker::PhantomData;
+use core::pin::Pin;
+
+/// Creates a [`Work`] initialiser with the given name and a newly-created lock class.
+#[macro_export]
+macro_rules! new_work {
+    ($($name:literal)?) => {
+        $crate::workqueue::Work::new($crate::optional_name!($($name)?), $crate::static_lock_class!())
+    };
+}
+
+/// A kernel work queue.
+///
+/// Wraps the kernel's C `struct workqueue_struct`.
+///
+/// It allows work items to be queued to run on thread pools managed by the kernel. Several are
+/// always available, for example, `system`, `system_highpri`, `system_long`, etc.
+#[repr(transparent)]
+pub struct Queue(Opaque<bindings::workqueue_struct>);
+
+// SAFETY: Accesses to workqueues used by [`Queue`] are thread-safe.
+unsafe impl Send for Queue {}
+// SAFETY: Accesses to workqueues used by [`Queue`] are thread-safe.
+unsafe impl Sync for Queue {}
+
+impl Queue {
+    /// Use the provided `struct workqueue_struct` with Rust.
+    ///
+    /// # Safety
+    ///
+    /// The caller must ensure that the provided raw pointer is not dangling, that it points at a
+    /// valid workqueue, and that it remains valid until the end of 'a.
+    pub unsafe fn from_raw<'a>(ptr: *const bindings::workqueue_struct) -> &'a Queue {
+        // SAFETY: The `Queue` type is `#[repr(transparent)]`, so the pointer cast is valid. The
+        // caller promises that the pointer is not dangling.
+        unsafe { &*(ptr as *const Queue) }
+    }
+
+    /// Enqueues a work item.
+    ///
+    /// This may fail if the work item is already enqueued in a workqueue.
+    ///
+    /// The work item will be submitted using `WORK_CPU_UNBOUND`.
+    pub fn enqueue<W, const ID: u64>(&self, w: W) -> W::EnqueueOutput
+    where
+        W: RawWorkItem<ID> + Send + 'static,
+    {
+        let queue_ptr = self.0.get();
+
+        // SAFETY: We only return `false` if the `work_struct` is already in a workqueue. The other
+        // `__enqueue` requirements are not relevant since `W` is `Send` and static.
+        //
+        // The call to `bindings::queue_work_on` will dereference the provided raw pointer, which
+        // is ok because `__enqueue` guarantees that the pointer is valid for the duration of this
+        // closure.
+        //
+        // Furthermore, if the C workqueue code accesses the pointer after this call to
+        // `__enqueue`, then the work item was successfully enqueued, and `bindings::queue_work_on`
+        // will have returned true. In this case, `__enqueue` promises that the raw pointer will
+        // stay valid until we call the function pointer in the `work_struct`, so the access is ok.
+        unsafe {
+            w.__enqueue(move |work_ptr| {
+                bindings::queue_work_on(bindings::WORK_CPU_UNBOUND as _, queue_ptr, work_ptr)
+            })
+        }
+    }
+
+    /// Tries to spawn the given function or closure as a work item.
+    ///
+    /// This method can fail because it allocates memory to store the work item.
+    pub fn try_spawn<T: 'static + Send + FnOnce()>(&self, func: T) -> Result<(), AllocError> {
+        let init = pin_init!(ClosureWork {
+            work <- new_work!("Queue::try_spawn"),
+            func: Some(func),
+        });
+
+        self.enqueue(Box::pin_init(init).map_err(|_| AllocError)?);
+        Ok(())
+    }
+}
+
+/// A helper type used in `try_spawn`.
+#[pin_data]
+struct ClosureWork<T> {
+    #[pin]
+    work: Work<ClosureWork<T>>,
+    func: Option<T>,
+}
+
+impl<T> ClosureWork<T> {
+    fn project(self: Pin<&mut Self>) -> &mut Option<T> {
+        // SAFETY: The `func` field is not structurally pinned.
+        unsafe { &mut self.get_unchecked_mut().func }
+    }
+}
+
+impl<T: FnOnce()> WorkItem for ClosureWork<T> {
+    type Pointer = Pin<Box<Self>>;
+
+    fn run(mut this: Pin<Box<Self>>) {
+        if let Some(func) = this.as_mut().project().take() {
+            (func)()
+        }
+    }
+}
+
+/// A raw work item.
+///
+/// This is the low-level trait that is designed for being as general as possible.
+///
+/// The `ID` parameter to this trait exists so that a single type can provide multiple
+/// implementations of this trait. For example, if a struct has multiple `work_struct` fields, then
+/// you will implement this trait once for each field, using a different id for each field. The
+/// actual value of the id is not important as long as you use different ids for different fields
+/// of the same struct. (Fields of different structs need not use different ids.)
+///
+/// Note that the id is used only to select the right method to call during compilation. It wont be
+/// part of the final executable.
+///
+/// # Safety
+///
+/// Implementers must ensure that any pointers passed to a `queue_work_on` closure by `__enqueue`
+/// remain valid for the duration specified in the guarantees section of the documentation for
+/// `__enqueue`.
+pub unsafe trait RawWorkItem<const ID: u64> {
+    /// The return type of [`Queue::enqueue`].
+    type EnqueueOutput;
+
+    /// Enqueues this work item on a queue using the provided `queue_work_on` method.
+    ///
+    /// # Guarantees
+    ///
+    /// If this method calls the provided closure, then the raw pointer is guaranteed to point at a
+    /// valid `work_struct` for the duration of the call to the closure. If the closure returns
+    /// true, then it is further guaranteed that the pointer remains valid until someone calls the
+    /// function pointer stored in the `work_struct`.
+    ///
+    /// # Safety
+    ///
+    /// The provided closure may only return `false` if the `work_struct` is already in a workqueue.
+    ///
+    /// If the work item type is annotated with any lifetimes, then you must not call the function
+    /// pointer after any such lifetime expires. (Never calling the function pointer is okay.)
+    ///
+    /// If the work item type is not [`Send`], then the function pointer must be called on the same
+    /// thread as the call to `__enqueue`.
+    unsafe fn __enqueue<F>(self, queue_work_on: F) -> Self::EnqueueOutput
+    where
+        F: FnOnce(*mut bindings::work_struct) -> bool;
+}
+
+/// Defines the method that should be called directly when a work item is executed.
+///
+/// This trait is implemented by `Pin<Box<T>>` and `Arc<T>`, and is mainly intended to be
+/// implemented for smart pointer types. For your own structs, you would implement [`WorkItem`]
+/// instead. The `run` method on this trait will usually just perform the appropriate
+/// `container_of` translation and then call into the `run` method from the [`WorkItem`] trait.
+///
+/// This trait is used when the `work_struct` field is defined using the [`Work`] helper.
+///
+/// # Safety
+///
+/// Implementers must ensure that [`__enqueue`] uses a `work_struct` initialized with the [`run`]
+/// method of this trait as the function pointer.
+///
+/// [`__enqueue`]: RawWorkItem::__enqueue
+/// [`run`]: WorkItemPointer::run
+pub unsafe trait WorkItemPointer<const ID: u64>: RawWorkItem<ID> {
+    /// Run this work item.
+    ///
+    /// # Safety
+    ///
+    /// The provided `work_struct` pointer must originate from a previous call to `__enqueue` where
+    /// the `queue_work_on` closure returned true, and the pointer must still be valid.
+    unsafe extern "C" fn run(ptr: *mut bindings::work_struct);
+}
+
+/// Defines the method that should be called when this work item is executed.
+///
+/// This trait is used when the `work_struct` field is defined using the [`Work`] helper.
+pub trait WorkItem<const ID: u64 = 0> {
+    /// The pointer type that this struct is wrapped in. This will typically be `Arc<Self>` or
+    /// `Pin<Box<Self>>`.
+    type Pointer: WorkItemPointer<ID>;
+
+    /// The method that should be called when this work item is executed.
+    fn run(this: Self::Pointer);
+}
+
+/// Links for a work item.
+///
+/// This struct contains a function pointer to the `run` function from the [`WorkItemPointer`]
+/// trait, and defines the linked list pointers necessary to enqueue a work item in a workqueue.
+///
+/// Wraps the kernel's C `struct work_struct`.
+///
+/// This is a helper type used to associate a `work_struct` with the [`WorkItem`] that uses it.
+#[repr(transparent)]
+pub struct Work<T: ?Sized, const ID: u64 = 0> {
+    work: Opaque<bindings::work_struct>,
+    _inner: PhantomData<T>,
+}
+
+// SAFETY: Kernel work items are usable from any thread.
+//
+// We do not need to constrain `T` since the work item does not actually contain a `T`.
+unsafe impl<T: ?Sized, const ID: u64> Send for Work<T, ID> {}
+// SAFETY: Kernel work items are usable from any thread.
+//
+// We do not need to constrain `T` since the work item does not actually contain a `T`.
+unsafe impl<T: ?Sized, const ID: u64> Sync for Work<T, ID> {}
+
+impl<T: ?Sized, const ID: u64> Work<T, ID> {
+    /// Creates a new instance of [`Work`].
+    #[inline]
+    #[allow(clippy::new_ret_no_self)]
+    pub fn new(name: &'static CStr, key: &'static LockClassKey) -> impl PinInit<Self>
+    where
+        T: WorkItem<ID>,
+    {
+        // SAFETY: The `WorkItemPointer` implementation promises that `run` can be used as the work
+        // item function.
+        unsafe {
+            kernel::init::pin_init_from_closure(move |slot| {
+                let slot = Self::raw_get(slot);
+                bindings::init_work_with_key(
+                    slot,
+                    Some(T::Pointer::run),
+                    false,
+                    name.as_char_ptr(),
+                    key.as_ptr(),
+                );
+                Ok(())
+            })
+        }
+    }
+
+    /// Get a pointer to the inner `work_struct`.
+    ///
+    /// # Safety
+    ///
+    /// The provided pointer must not be dangling and must be properly aligned. (But the memory
+    /// need not be initialized.)
+    #[inline]
+    pub unsafe fn raw_get(ptr: *const Self) -> *mut bindings::work_struct {
+        // SAFETY: The caller promises that the pointer is aligned and not dangling.
+        //
+        // A pointer cast would also be ok due to `#[repr(transparent)]`. We use `addr_of!` so that
+        // the compiler does not complain that the `work` field is unused.
+        unsafe { Opaque::raw_get(core::ptr::addr_of!((*ptr).work)) }
+    }
+}
+
+/// Declares that a type has a [`Work<T, ID>`] field.
+///
+/// The intended way of using this trait is via the [`impl_has_work!`] macro. You can use the macro
+/// like this:
+///
+/// ```no_run
+/// use kernel::impl_has_work;
+/// use kernel::prelude::*;
+/// use kernel::workqueue::Work;
+///
+/// struct MyWorkItem {
+///     work_field: Work<MyWorkItem, 1>,
+/// }
+///
+/// impl_has_work! {
+///     impl HasWork<MyWorkItem, 1> for MyWorkItem { self.work_field }
+/// }
+/// ```
+///
+/// Note that since the `Work` type is annotated with an id, you can have several `work_struct`
+/// fields by using a different id for each one.
+///
+/// # Safety
+///
+/// The [`OFFSET`] constant must be the offset of a field in Self of type [`Work<T, ID>`]. The methods on
+/// this trait must have exactly the behavior that the definitions given below have.
+///
+/// [`Work<T, ID>`]: Work
+/// [`impl_has_work!`]: crate::impl_has_work
+/// [`OFFSET`]: HasWork::OFFSET
+pub unsafe trait HasWork<T, const ID: u64 = 0> {
+    /// The offset of the [`Work<T, ID>`] field.
+    ///
+    /// [`Work<T, ID>`]: Work
+    const OFFSET: usize;
+
+    /// Returns the offset of the [`Work<T, ID>`] field.
+    ///
+    /// This method exists because the [`OFFSET`] constant cannot be accessed if the type is not Sized.
+    ///
+    /// [`Work<T, ID>`]: Work
+    /// [`OFFSET`]: HasWork::OFFSET
+    #[inline]
+    fn get_work_offset(&self) -> usize {
+        Self::OFFSET
+    }
+
+    /// Returns a pointer to the [`Work<T, ID>`] field.
+    ///
+    /// # Safety
+    ///
+    /// The provided pointer must point at a valid struct of type `Self`.
+    ///
+    /// [`Work<T, ID>`]: Work
+    #[inline]
+    unsafe fn raw_get_work(ptr: *mut Self) -> *mut Work<T, ID> {
+        // SAFETY: The caller promises that the pointer is valid.
+        unsafe { (ptr as *mut u8).add(Self::OFFSET) as *mut Work<T, ID> }
+    }
+
+    /// Returns a pointer to the struct containing the [`Work<T, ID>`] field.
+    ///
+    /// # Safety
+    ///
+    /// The pointer must point at a [`Work<T, ID>`] field in a struct of type `Self`.
+    ///
+    /// [`Work<T, ID>`]: Work
+    #[inline]
+    unsafe fn work_container_of(ptr: *mut Work<T, ID>) -> *mut Self
+    where
+        Self: Sized,
+    {
+        // SAFETY: The caller promises that the pointer points at a field of the right type in the
+        // right kind of struct.
+        unsafe { (ptr as *mut u8).sub(Self::OFFSET) as *mut Self }
+    }
+}
+
+/// Used to safely implement the [`HasWork<T, ID>`] trait.
+///
+/// # Examples
+///
+/// ```
+/// use kernel::impl_has_work;
+/// use kernel::sync::Arc;
+/// use kernel::workqueue::{self, Work};
+///
+/// struct MyStruct {
+///     work_field: Work<MyStruct, 17>,
+/// }
+///
+/// impl_has_work! {
+///     impl HasWork<MyStruct, 17> for MyStruct { self.work_field }
+/// }
+/// ```
+///
+/// [`HasWork<T, ID>`]: HasWork
+#[macro_export]
+macro_rules! impl_has_work {
+    ($(impl$(<$($implarg:ident),*>)?
+       HasWork<$work_type:ty $(, $id:tt)?>
+       for $self:ident $(<$($selfarg:ident),*>)?
+       { self.$field:ident }
+    )*) => {$(
+        // SAFETY: The implementation of `raw_get_work` only compiles if the field has the right
+        // type.
+        unsafe impl$(<$($implarg),*>)? $crate::workqueue::HasWork<$work_type $(, $id)?> for $self $(<$($selfarg),*>)? {
+            const OFFSET: usize = ::core::mem::offset_of!(Self, $field) as usize;
+
+            #[inline]
+            unsafe fn raw_get_work(ptr: *mut Self) -> *mut $crate::workqueue::Work<$work_type $(, $id)?> {
+                // SAFETY: The caller promises that the pointer is not dangling.
+                unsafe {
+                    ::core::ptr::addr_of_mut!((*ptr).$field)
+                }
+            }
+        }
+    )*};
+}
+
+impl_has_work! {
+    impl<T> HasWork<Self> for ClosureWork<T> { self.work }
+}
+
+unsafe impl<T, const ID: u64> WorkItemPointer<ID> for Arc<T>
+where
+    T: WorkItem<ID, Pointer = Self>,
+    T: HasWork<T, ID>,
+{
+    unsafe extern "C" fn run(ptr: *mut bindings::work_struct) {
+        // SAFETY: The `__enqueue` method always uses a `work_struct` stored in a `Work<T, ID>`.
+        let ptr = ptr as *mut Work<T, ID>;
+        // SAFETY: This computes the pointer that `__enqueue` got from `Arc::into_raw`.
+        let ptr = unsafe { T::work_container_of(ptr) };
+        // SAFETY: This pointer comes from `Arc::into_raw` and we've been given back ownership.
+        let arc = unsafe { Arc::from_raw(ptr) };
+
+        T::run(arc)
+    }
+}
+
+unsafe impl<T, const ID: u64> RawWorkItem<ID> for Arc<T>
+where
+    T: WorkItem<ID, Pointer = Self>,
+    T: HasWork<T, ID>,
+{
+    type EnqueueOutput = Result<(), Self>;
+
+    unsafe fn __enqueue<F>(self, queue_work_on: F) -> Self::EnqueueOutput
+    where
+        F: FnOnce(*mut bindings::work_struct) -> bool,
+    {
+        // Casting between const and mut is not a problem as long as the pointer is a raw pointer.
+        let ptr = Arc::into_raw(self).cast_mut();
+
+        // SAFETY: Pointers into an `Arc` point at a valid value.
+        let work_ptr = unsafe { T::raw_get_work(ptr) };
+        // SAFETY: `raw_get_work` returns a pointer to a valid value.
+        let work_ptr = unsafe { Work::raw_get(work_ptr) };
+
+        if queue_work_on(work_ptr) {
+            Ok(())
+        } else {
+            // SAFETY: The work queue has not taken ownership of the pointer.
+            Err(unsafe { Arc::from_raw(ptr) })
+        }
+    }
+}
+
+unsafe impl<T, const ID: u64> WorkItemPointer<ID> for Pin<Box<T>>
+where
+    T: WorkItem<ID, Pointer = Self>,
+    T: HasWork<T, ID>,
+{
+    unsafe extern "C" fn run(ptr: *mut bindings::work_struct) {
+        // SAFETY: The `__enqueue` method always uses a `work_struct` stored in a `Work<T, ID>`.
+        let ptr = ptr as *mut Work<T, ID>;
+        // SAFETY: This computes the pointer that `__enqueue` got from `Arc::into_raw`.
+        let ptr = unsafe { T::work_container_of(ptr) };
+        // SAFETY: This pointer comes from `Arc::into_raw` and we've been given back ownership.
+        let boxed = unsafe { Box::from_raw(ptr) };
+        // SAFETY: The box was already pinned when it was enqueued.
+        let pinned = unsafe { Pin::new_unchecked(boxed) };
+
+        T::run(pinned)
+    }
+}
+
+unsafe impl<T, const ID: u64> RawWorkItem<ID> for Pin<Box<T>>
+where
+    T: WorkItem<ID, Pointer = Self>,
+    T: HasWork<T, ID>,
+{
+    type EnqueueOutput = ();
+
+    unsafe fn __enqueue<F>(self, queue_work_on: F) -> Self::EnqueueOutput
+    where
+        F: FnOnce(*mut bindings::work_struct) -> bool,
+    {
+        // SAFETY: We're not going to move `self` or any of its fields, so its okay to temporarily
+        // remove the `Pin` wrapper.
+        let boxed = unsafe { Pin::into_inner_unchecked(self) };
+        let ptr = Box::into_raw(boxed);
+
+        // SAFETY: Pointers into a `Box` point at a valid value.
+        let work_ptr = unsafe { T::raw_get_work(ptr) };
+        // SAFETY: `raw_get_work` returns a pointer to a valid value.
+        let work_ptr = unsafe { Work::raw_get(work_ptr) };
+
+        if !queue_work_on(work_ptr) {
+            // SAFETY: This method requires exclusive ownership of the box, so it cannot be in a
+            // workqueue.
+            unsafe { ::core::hint::unreachable_unchecked() }
+        }
+    }
+}
+
+/// Returns the system work queue (`system_wq`).
+///
+/// It is the one used by `schedule[_delayed]_work[_on]()`. Multi-CPU multi-threaded. There are
+/// users which expect relatively short queue flush time.
+///
+/// Callers shouldn't queue work items which can run for too long.
+pub fn system() -> &'static Queue {
+    // SAFETY: `system_wq` is a C global, always available.
+    unsafe { Queue::from_raw(bindings::system_wq) }
+}
+
+/// Returns the system high-priority work queue (`system_highpri_wq`).
+///
+/// It is similar to the one returned by [`system`] but for work items which require higher
+/// scheduling priority.
+pub fn system_highpri() -> &'static Queue {
+    // SAFETY: `system_highpri_wq` is a C global, always available.
+    unsafe { Queue::from_raw(bindings::system_highpri_wq) }
+}
+
+/// Returns the system work queue for potentially long-running work items (`system_long_wq`).
+///
+/// It is similar to the one returned by [`system`] but may host long running work items. Queue
+/// flushing might take relatively long.
+pub fn system_long() -> &'static Queue {
+    // SAFETY: `system_long_wq` is a C global, always available.
+    unsafe { Queue::from_raw(bindings::system_long_wq) }
+}
+
+/// Returns the system unbound work queue (`system_unbound_wq`).
+///
+/// Workers are not bound to any specific CPU, not concurrency managed, and all queued work items
+/// are executed immediately as long as `max_active` limit is not reached and resources are
+/// available.
+pub fn system_unbound() -> &'static Queue {
+    // SAFETY: `system_unbound_wq` is a C global, always available.
+    unsafe { Queue::from_raw(bindings::system_unbound_wq) }
+}
+
+/// Returns the system freezable work queue (`system_freezable_wq`).
+///
+/// It is equivalent to the one returned by [`system`] except that it's freezable.
+///
+/// A freezable workqueue participates in the freeze phase of the system suspend operations. Work
+/// items on the workqueue are drained and no new work item starts execution until thawed.
+pub fn system_freezable() -> &'static Queue {
+    // SAFETY: `system_freezable_wq` is a C global, always available.
+    unsafe { Queue::from_raw(bindings::system_freezable_wq) }
+}
+
+/// Returns the system power-efficient work queue (`system_power_efficient_wq`).
+///
+/// It is inclined towards saving power and is converted to "unbound" variants if the
+/// `workqueue.power_efficient` kernel parameter is specified; otherwise, it is similar to the one
+/// returned by [`system`].
+pub fn system_power_efficient() -> &'static Queue {
+    // SAFETY: `system_power_efficient_wq` is a C global, always available.
+    unsafe { Queue::from_raw(bindings::system_power_efficient_wq) }
+}
+
+/// Returns the system freezable power-efficient work queue (`system_freezable_power_efficient_wq`).
+///
+/// It is similar to the one returned by [`system_power_efficient`] except that is freezable.
+///
+/// A freezable workqueue participates in the freeze phase of the system suspend operations. Work
+/// items on the workqueue are drained and no new work item starts execution until thawed.
+pub fn system_freezable_power_efficient() -> &'static Queue {
+    // SAFETY: `system_freezable_power_efficient_wq` is a C global, always available.
+    unsafe { Queue::from_raw(bindings::system_freezable_power_efficient_wq) }
+}