diff options
author | Wedson Almeida Filho <wedsonaf@gmail.com> | 2023-01-30 03:44:01 -0300 |
---|---|---|
committer | Miguel Ojeda <ojeda@kernel.org> | 2023-02-01 13:24:07 +0100 |
commit | 0fc4424d24a230c7fb539d5d708c81c68aafa9be (patch) | |
tree | f7ff45a3ee2b205e257225d941c23b5e019789e8 /rust | |
parent | 4d4692a2ff836487c17960a6211a4cce7094f09c (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.rs | 1 | ||||
-rw-r--r-- | rust/kernel/types.rs | 54 |
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. |