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authorBenno Lossin <benno.lossin@proton.me>2023-08-14 08:47:48 +0000
committerMiguel Ojeda <ojeda@kernel.org>2023-08-21 14:31:49 +0200
commit7f8977a7fe6df9cdfe489c641058ca5534ec73eb (patch)
treedf8a424a9413189899c2033199ad86918a4d54b2
parent1a8076ac6d83825bedb2050e67db0f2635acbb09 (diff)
rust: init: add `{pin_}chain` functions to `{Pin}Init<T, E>`
The `{pin_}chain` functions extend an initializer: it not only initializes the value, but also executes a closure taking a reference to the initialized value. This allows to do something with a value directly after initialization. Suggested-by: Asahi Lina <lina@asahilina.net> Reviewed-by: Martin Rodriguez Reboredo <yakoyoku@gmail.com> Signed-off-by: Benno Lossin <benno.lossin@proton.me> Reviewed-by: Alice Ryhl <aliceryhl@google.com> Link: https://lore.kernel.org/r/20230814084602.25699-13-benno.lossin@proton.me [ Cleaned a few trivial nits. ] Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
-rw-r--r--rust/kernel/init.rs142
-rw-r--r--rust/kernel/init/__internal.rs2
2 files changed, 143 insertions, 1 deletions
diff --git a/rust/kernel/init.rs b/rust/kernel/init.rs
index 0f9c8576697e..0071b2834b78 100644
--- a/rust/kernel/init.rs
+++ b/rust/kernel/init.rs
@@ -767,6 +767,79 @@ pub unsafe trait PinInit<T: ?Sized, E = Infallible>: Sized {
/// deallocate.
/// - `slot` will not move until it is dropped, i.e. it will be pinned.
unsafe fn __pinned_init(self, slot: *mut T) -> Result<(), E>;
+
+ /// First initializes the value using `self` then calls the function `f` with the initialized
+ /// value.
+ ///
+ /// If `f` returns an error the value is dropped and the initializer will forward the error.
+ ///
+ /// # Examples
+ ///
+ /// ```rust
+ /// # #![allow(clippy::disallowed_names)]
+ /// use kernel::{types::Opaque, init::pin_init_from_closure};
+ /// #[repr(C)]
+ /// struct RawFoo([u8; 16]);
+ /// extern {
+ /// fn init_foo(_: *mut RawFoo);
+ /// }
+ ///
+ /// #[pin_data]
+ /// struct Foo {
+ /// #[pin]
+ /// raw: Opaque<RawFoo>,
+ /// }
+ ///
+ /// impl Foo {
+ /// fn setup(self: Pin<&mut Self>) {
+ /// pr_info!("Setting up foo");
+ /// }
+ /// }
+ ///
+ /// let foo = pin_init!(Foo {
+ /// raw <- unsafe {
+ /// Opaque::ffi_init(|s| {
+ /// init_foo(s);
+ /// })
+ /// },
+ /// }).pin_chain(|foo| {
+ /// foo.setup();
+ /// Ok(())
+ /// });
+ /// ```
+ fn pin_chain<F>(self, f: F) -> ChainPinInit<Self, F, T, E>
+ where
+ F: FnOnce(Pin<&mut T>) -> Result<(), E>,
+ {
+ ChainPinInit(self, f, PhantomData)
+ }
+}
+
+/// An initializer returned by [`PinInit::pin_chain`].
+pub struct ChainPinInit<I, F, T: ?Sized, E>(I, F, __internal::Invariant<(E, Box<T>)>);
+
+// SAFETY: The `__pinned_init` function is implemented such that it
+// - returns `Ok(())` on successful initialization,
+// - returns `Err(err)` on error and in this case `slot` will be dropped.
+// - considers `slot` pinned.
+unsafe impl<T: ?Sized, E, I, F> PinInit<T, E> for ChainPinInit<I, F, T, E>
+where
+ I: PinInit<T, E>,
+ F: FnOnce(Pin<&mut T>) -> Result<(), E>,
+{
+ unsafe fn __pinned_init(self, slot: *mut T) -> Result<(), E> {
+ // SAFETY: All requirements fulfilled since this function is `__pinned_init`.
+ unsafe { self.0.__pinned_init(slot)? };
+ // SAFETY: The above call initialized `slot` and we still have unique access.
+ let val = unsafe { &mut *slot };
+ // SAFETY: `slot` is considered pinned.
+ let val = unsafe { Pin::new_unchecked(val) };
+ (self.1)(val).map_err(|e| {
+ // SAFETY: `slot` was initialized above.
+ unsafe { core::ptr::drop_in_place(slot) };
+ e
+ })
+ }
}
/// An initializer for `T`.
@@ -808,6 +881,75 @@ pub unsafe trait Init<T: ?Sized, E = Infallible>: PinInit<T, E> {
/// - the caller does not touch `slot` when `Err` is returned, they are only permitted to
/// deallocate.
unsafe fn __init(self, slot: *mut T) -> Result<(), E>;
+
+ /// First initializes the value using `self` then calls the function `f` with the initialized
+ /// value.
+ ///
+ /// If `f` returns an error the value is dropped and the initializer will forward the error.
+ ///
+ /// # Examples
+ ///
+ /// ```rust
+ /// # #![allow(clippy::disallowed_names)]
+ /// use kernel::{types::Opaque, init::{self, init_from_closure}};
+ /// struct Foo {
+ /// buf: [u8; 1_000_000],
+ /// }
+ ///
+ /// impl Foo {
+ /// fn setup(&mut self) {
+ /// pr_info!("Setting up foo");
+ /// }
+ /// }
+ ///
+ /// let foo = init!(Foo {
+ /// buf <- init::zeroed()
+ /// }).chain(|foo| {
+ /// foo.setup();
+ /// Ok(())
+ /// });
+ /// ```
+ fn chain<F>(self, f: F) -> ChainInit<Self, F, T, E>
+ where
+ F: FnOnce(&mut T) -> Result<(), E>,
+ {
+ ChainInit(self, f, PhantomData)
+ }
+}
+
+/// An initializer returned by [`Init::chain`].
+pub struct ChainInit<I, F, T: ?Sized, E>(I, F, __internal::Invariant<(E, Box<T>)>);
+
+// SAFETY: The `__init` function is implemented such that it
+// - returns `Ok(())` on successful initialization,
+// - returns `Err(err)` on error and in this case `slot` will be dropped.
+unsafe impl<T: ?Sized, E, I, F> Init<T, E> for ChainInit<I, F, T, E>
+where
+ I: Init<T, E>,
+ F: FnOnce(&mut T) -> Result<(), E>,
+{
+ unsafe fn __init(self, slot: *mut T) -> Result<(), E> {
+ // SAFETY: All requirements fulfilled since this function is `__init`.
+ unsafe { self.0.__pinned_init(slot)? };
+ // SAFETY: The above call initialized `slot` and we still have unique access.
+ (self.1)(unsafe { &mut *slot }).map_err(|e| {
+ // SAFETY: `slot` was initialized above.
+ unsafe { core::ptr::drop_in_place(slot) };
+ e
+ })
+ }
+}
+
+// SAFETY: `__pinned_init` behaves exactly the same as `__init`.
+unsafe impl<T: ?Sized, E, I, F> PinInit<T, E> for ChainInit<I, F, T, E>
+where
+ I: Init<T, E>,
+ F: FnOnce(&mut T) -> Result<(), E>,
+{
+ unsafe fn __pinned_init(self, slot: *mut T) -> Result<(), E> {
+ // SAFETY: `__init` has less strict requirements compared to `__pinned_init`.
+ unsafe { self.__init(slot) }
+ }
}
/// Creates a new [`PinInit<T, E>`] from the given closure.
diff --git a/rust/kernel/init/__internal.rs b/rust/kernel/init/__internal.rs
index 12e195061525..db3372619ecd 100644
--- a/rust/kernel/init/__internal.rs
+++ b/rust/kernel/init/__internal.rs
@@ -13,7 +13,7 @@ use super::*;
///
/// [nomicon]: https://doc.rust-lang.org/nomicon/subtyping.html
/// [this table]: https://doc.rust-lang.org/nomicon/phantom-data.html#table-of-phantomdata-patterns
-type Invariant<T> = PhantomData<fn(*mut T) -> *mut T>;
+pub(super) type Invariant<T> = PhantomData<fn(*mut T) -> *mut T>;
/// This is the module-internal type implementing `PinInit` and `Init`. It is unsafe to create this
/// type, since the closure needs to fulfill the same safety requirement as the