[PATCH 1/3] rust: types: add Opaque::try_ffi_init

Alice Ryhl
2024-09-26T14:59:39Z

This will be used by the miscdevice abstractions, as the C function
`misc_register` is fallible.

Signed-off-by: Alice Ryhl <aliceryhl@google.com>
---
rust/kernel/types.rs | 16 ++++++++++++++++
1 file changed, 16 insertions(+)

diff --git a/rust/kernel/types.rs b/rust/kernel/types.rs
index 3238ffaab031..dd9c606c515c 100644
--- a/rust/kernel/types.rs
+++ b/rust/kernel/types.rs
@@ -299,6 +299,22 @@ pub fn ffi_init(init_func: impl FnOnce(*mut T)) -> impl PinInit<Self> {
}
}

+ /// Creates a fallible pin-initializer from the given initializer closure.
+ ///
+ /// The returned initializer calls the given closure with the pointer to the inner `T` of this
+ /// `Opaque`. Since this memory is uninitialized, the closure is not allowed to read from it.
+ ///
+ /// This function is safe, because the `T` inside of an `Opaque` is allowed to be
+ /// uninitialized. Additionally, access to the inner `T` requires `unsafe`, so the caller needs
+ /// to verify at that point that the inner value is valid.
+ pub fn try_ffi_init<E>(
+ init_func: impl FnOnce(*mut T) -> Result<(), E>,
+ ) -> impl PinInit<Self, E> {
+ // SAFETY: We contain a `MaybeUninit`, so it is OK for the `init_func` to not fully
+ // initialize the `T`.
+ unsafe { init::pin_init_from_closure::<_, E>(move |slot| init_func(Self::raw_get(slot))) }
+ }
+
/// Returns a raw pointer to the opaque data.
pub const fn get(&self) -> *mut T {
UnsafeCell::get(&self.value).cast::<T>()

--
2.46.0.792.g87dc391469-goog