Re: [PATCH 4/4] rust: devres: do not dereference to the internal Revocable

[Sasha Levin <sashal@kernel.org>]

[ Sasha's backport helper bot ]

Hi,

✅ All tests passed successfully. No issues detected.
No action required from the submitter.

The upstream commit SHA1 provided is correct: 20c96ed278e362ae4e324ed7d8c69fb48c508d3c

Note: The patch differs from the upstream commit:
---
1:  20c96ed278e36 ! 1:  c56dfa9d4bad7 rust: devres: do not dereference to the internal Revocable
    @@ Metadata
      ## Commit message ##
         rust: devres: do not dereference to the internal Revocable
     
    +    [ Upstream commit 20c96ed278e362ae4e324ed7d8c69fb48c508d3c ]
    +
         We can't expose direct access to the internal Revocable, since this
         allows users to directly revoke the internal Revocable without Devres
         having the chance to synchronize with the devres callback -- we have to
    @@ rust/kernel/devres.rs
      #[pin_data]
      struct DevresInner<T> {
          dev: ARef<Device>,
    -@@ rust/kernel/devres.rs: pub fn access<'a>(&'a self, dev: &'a Device<Bound>) -> Result<&'a T> {
    -         // SAFETY: `dev` being the same device as the device this `Devres` has been created for
    -         // proves that `self.0.data` hasn't been revoked and is guaranteed to not be revoked as
    -         // long as `dev` lives; `dev` lives at least as long as `self`.
    --        Ok(unsafe { self.deref().access() })
    -+        Ok(unsafe { self.0.data.access() })
    +@@ rust/kernel/devres.rs: pub fn new_foreign_owned(dev: &Device, data: T, flags: Flags) -> Result {
    + 
    +         Ok(())
          }
     -}
      
    @@ rust/kernel/devres.rs: pub fn access<'a>(&'a self, dev: &'a Device<Bound>) -> Re
     +    pub fn try_access(&self) -> Option<RevocableGuard<'_, T>> {
     +        self.0.data.try_access()
     +    }
    -+
    -+    /// [`Devres`] accessor for [`Revocable::try_access_with`].
    -+    pub fn try_access_with<R, F: FnOnce(&T) -> R>(&self, f: F) -> Option<R> {
    -+        self.0.data.try_access_with(f)
    -+    }
      
     -    fn deref(&self) -> &Self::Target {
     -        &self.0.data
---

Results of testing on various branches:

| Branch                    | Patch Apply | Build Test |
|---------------------------|-------------|------------|
| stable/linux-5.4.y        |  Success    |  Success   |