linux-kernel - [PATCH 1/3] rust: revocable: implement Revocable::access()

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Message-ID: <20250426133254.61383-2-dakr@kernel.org>
Date: Sat, 26 Apr 2025 15:30:39 +0200
From: Danilo Krummrich <dakr@...nel.org>
To: gregkh@...uxfoundation.org,
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Cc: linux-pci@...r.kernel.org,
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	linux-kernel@...r.kernel.org,
	Danilo Krummrich <dakr@...nel.org>
Subject: [PATCH 1/3] rust: revocable: implement Revocable::access()

Implement an unsafe direct accessor for the data stored within the
Revocable.

This is useful for cases where we can proof that the data stored within
the Revocable is not and cannot be revoked for the duration of the
lifetime of the returned reference.

Signed-off-by: Danilo Krummrich <dakr@...nel.org>
---
The explicit lifetimes in access() probably don't serve a practical
purpose, but I found them to be useful for documentation purposes.
---
 rust/kernel/revocable.rs | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/rust/kernel/revocable.rs b/rust/kernel/revocable.rs
index 971d0dc38d83..33535de141ce 100644
--- a/rust/kernel/revocable.rs
+++ b/rust/kernel/revocable.rs
@@ -139,6 +139,18 @@ pub fn try_access_with<R, F: FnOnce(&T) -> R>(&self, f: F) -> Option<R> {
         self.try_access().map(|t| f(&*t))
     }
 
+    /// Directly access the revocable wrapped object.
+    ///
+    /// # Safety
+    ///
+    /// The caller must ensure this [`Revocable`] instance hasn't been revoked and won't be revoked
+    /// for the duration of `'a`.
+    pub unsafe fn access<'a, 's: 'a>(&'s self) -> &'a T {
+        // SAFETY: By the safety requirement of this function it is guaranteed that
+        // `self.data.get()` is a valid pointer to an instance of `T`.
+        unsafe { &*self.data.get() }
+    }
+
     /// # Safety
     ///
     /// Callers must ensure that there are no more concurrent users of the revocable object.
-- 
2.49.0