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authorWedson Almeida Filho <wedsonaf@gmail.com>2023-01-30 03:44:01 -0300
committerMiguel Ojeda <ojeda@kernel.org>2023-02-01 13:24:07 +0100
commit0fc4424d24a230c7fb539d5d708c81c68aafa9be (patch)
treef7ff45a3ee2b205e257225d941c23b5e019789e8 /rust
parent4d4692a2ff836487c17960a6211a4cce7094f09c (diff)
rust: types: introduce `ForeignOwnable`
It was originally called `PointerWrapper`. It is used to convert a Rust object to a pointer representation (void *) that can be stored on the C side, used, and eventually returned to Rust. Signed-off-by: Wedson Almeida Filho <wedsonaf@gmail.com> Reviewed-by: Vincenzo Palazzo <vincenzopalazzodev@gmail.com> Reviewed-by: Martin Rodriguez Reboredo <yakoyoku@gmail.com> Reviewed-by: Gary Guo <gary@garyguo.net> Reviewed-by: Andreas Hindborg <a.hindborg@samsung.com> Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
Diffstat (limited to 'rust')
-rw-r--r--rust/kernel/lib.rs1
-rw-r--r--rust/kernel/types.rs54
2 files changed, 55 insertions, 0 deletions
diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
index e0b0e953907d..223564f9f0cc 100644
--- a/rust/kernel/lib.rs
+++ b/rust/kernel/lib.rs
@@ -16,6 +16,7 @@
#![feature(coerce_unsized)]
#![feature(core_ffi_c)]
#![feature(dispatch_from_dyn)]
+#![feature(generic_associated_types)]
#![feature(receiver_trait)]
#![feature(unsize)]
diff --git a/rust/kernel/types.rs b/rust/kernel/types.rs
index dd834bfcb57b..72710b7442a3 100644
--- a/rust/kernel/types.rs
+++ b/rust/kernel/types.rs
@@ -8,6 +8,60 @@ use core::{
ops::{Deref, DerefMut},
};
+/// Used to transfer ownership to and from foreign (non-Rust) languages.
+///
+/// Ownership is transferred from Rust to a foreign language by calling [`Self::into_foreign`] and
+/// later may be transferred back to Rust by calling [`Self::from_foreign`].
+///
+/// This trait is meant to be used in cases when Rust objects are stored in C objects and
+/// eventually "freed" back to Rust.
+pub trait ForeignOwnable: Sized {
+ /// Type of values borrowed between calls to [`ForeignOwnable::into_foreign`] and
+ /// [`ForeignOwnable::from_foreign`].
+ type Borrowed<'a>;
+
+ /// Converts a Rust-owned object to a foreign-owned one.
+ ///
+ /// The foreign representation is a pointer to void.
+ fn into_foreign(self) -> *const core::ffi::c_void;
+
+ /// Borrows a foreign-owned object.
+ ///
+ /// # Safety
+ ///
+ /// `ptr` must have been returned by a previous call to [`ForeignOwnable::into_foreign`] for
+ /// which a previous matching [`ForeignOwnable::from_foreign`] hasn't been called yet.
+ /// Additionally, all instances (if any) of values returned by [`ForeignOwnable::borrow_mut`]
+ /// for this object must have been dropped.
+ unsafe fn borrow<'a>(ptr: *const core::ffi::c_void) -> Self::Borrowed<'a>;
+
+ /// Mutably borrows a foreign-owned object.
+ ///
+ /// # Safety
+ ///
+ /// `ptr` must have been returned by a previous call to [`ForeignOwnable::into_foreign`] for
+ /// which a previous matching [`ForeignOwnable::from_foreign`] hasn't been called yet.
+ /// Additionally, all instances (if any) of values returned by [`ForeignOwnable::borrow`] and
+ /// [`ForeignOwnable::borrow_mut`] for this object must have been dropped.
+ unsafe fn borrow_mut(ptr: *const core::ffi::c_void) -> ScopeGuard<Self, fn(Self)> {
+ // SAFETY: The safety requirements ensure that `ptr` came from a previous call to
+ // `into_foreign`.
+ ScopeGuard::new_with_data(unsafe { Self::from_foreign(ptr) }, |d| {
+ d.into_foreign();
+ })
+ }
+
+ /// Converts a foreign-owned object back to a Rust-owned one.
+ ///
+ /// # Safety
+ ///
+ /// `ptr` must have been returned by a previous call to [`ForeignOwnable::into_foreign`] for
+ /// which a previous matching [`ForeignOwnable::from_foreign`] hasn't been called yet.
+ /// Additionally, all instances (if any) of values returned by [`ForeignOwnable::borrow`] and
+ /// [`ForeignOwnable::borrow_mut`] for this object must have been dropped.
+ unsafe fn from_foreign(ptr: *const core::ffi::c_void) -> Self;
+}
+
/// Runs a cleanup function/closure when dropped.
///
/// The [`ScopeGuard::dismiss`] function prevents the cleanup function from running.