From 24799831d631239ff21ea1bf7feee832df48b81f Mon Sep 17 00:00:00 2001
From: Danilo Krummrich <dakr@kernel.org>
Date: Mon, 25 May 2026 22:20:58 +0200
Subject: rust: device: make Core and CoreInternal lifetime-parameterized

Device<Core> references in probe callbacks are scoped to the callback,
not the full binding duration. Add a lifetime parameter to Core and
CoreInternal to accurately represent this in the type system.

Suggested-by: Gary Guo <gary@garyguo.net>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Reviewed-by: Eliot Courtney <ecourtney@nvidia.com>
Reviewed-by: Gary Guo <gary@garyguo.net>
Link: https://patch.msgid.link/20260525202921.124698-12-dakr@kernel.org
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
---
 rust/kernel/device.rs | 49 ++++++++++++++++++++++++++++++++++++++-----------
 1 file changed, 38 insertions(+), 11 deletions(-)

(limited to 'rust/kernel/device.rs')

diff --git a/rust/kernel/device.rs b/rust/kernel/device.rs
index c4486f4b8c40..645afc49a27d 100644
--- a/rust/kernel/device.rs
+++ b/rust/kernel/device.rs
@@ -201,7 +201,7 @@ impl Device {
     }
 }
 
-impl Device<CoreInternal> {
+impl<'a> Device<CoreInternal<'a>> {
     /// Store a pointer to the bound driver's private data.
     pub fn set_drvdata<T>(&self, data: impl PinInit<T, Error>) -> Result {
         let data = KBox::pin_init(data, GFP_KERNEL)?;
@@ -511,7 +511,7 @@ pub struct Normal;
 /// callback it appears in. It is intended to be used for synchronization purposes. Bus device
 /// implementations can implement methods for [`Device<Core>`], such that they can only be called
 /// from bus callbacks.
-pub struct Core;
+pub struct Core<'a>(PhantomData<&'a ()>);
 
 /// Semantically the same as [`Core`], but reserved for internal usage of the corresponding bus
 /// abstraction.
@@ -522,7 +522,7 @@ pub struct Core;
 ///
 /// This context mainly exists to share generic [`Device`] infrastructure that should only be called
 /// from bus callbacks with bus abstractions, but without making them accessible for drivers.
-pub struct CoreInternal;
+pub struct CoreInternal<'a>(PhantomData<&'a ()>);
 
 /// The [`Bound`] context is the [`DeviceContext`] of a bus specific device when it is guaranteed to
 /// be bound to a driver.
@@ -546,14 +546,14 @@ mod private {
     pub trait Sealed {}
 
     impl Sealed for super::Bound {}
-    impl Sealed for super::Core {}
-    impl Sealed for super::CoreInternal {}
+    impl<'a> Sealed for super::Core<'a> {}
+    impl<'a> Sealed for super::CoreInternal<'a> {}
     impl Sealed for super::Normal {}
 }
 
 impl DeviceContext for Bound {}
-impl DeviceContext for Core {}
-impl DeviceContext for CoreInternal {}
+impl<'a> DeviceContext for Core<'a> {}
+impl<'a> DeviceContext for CoreInternal<'a> {}
 impl DeviceContext for Normal {}
 
 impl<Ctx: DeviceContext> AsRef<Device<Ctx>> for Device<Ctx> {
@@ -603,6 +603,22 @@ pub unsafe trait AsBusDevice<Ctx: DeviceContext>: AsRef<Device<Ctx>> {
 #[doc(hidden)]
 #[macro_export]
 macro_rules! __impl_device_context_deref {
+    (unsafe { $device:ident, <$lt:lifetime> $src:ty => $dst:ty }) => {
+        impl<$lt> ::core::ops::Deref for $device<$src> {
+            type Target = $device<$dst>;
+
+            fn deref(&self) -> &Self::Target {
+                let ptr: *const Self = self;
+
+                // CAST: `$device<$src>` and `$device<$dst>` transparently wrap the same type by the
+                // safety requirement of the macro.
+                let ptr = ptr.cast::<Self::Target>();
+
+                // SAFETY: `ptr` was derived from `&self`.
+                unsafe { &*ptr }
+            }
+        }
+    };
     (unsafe { $device:ident, $src:ty => $dst:ty }) => {
         impl ::core::ops::Deref for $device<$src> {
             type Target = $device<$dst>;
@@ -635,14 +651,14 @@ macro_rules! impl_device_context_deref {
         // `__impl_device_context_deref!`.
         ::kernel::__impl_device_context_deref!(unsafe {
             $device,
-            $crate::device::CoreInternal => $crate::device::Core
+            <'a> $crate::device::CoreInternal<'a> => $crate::device::Core<'a>
         });
 
         // SAFETY: This macro has the exact same safety requirement as
         // `__impl_device_context_deref!`.
         ::kernel::__impl_device_context_deref!(unsafe {
             $device,
-            $crate::device::Core => $crate::device::Bound
+            <'a> $crate::device::Core<'a> => $crate::device::Bound
         });
 
         // SAFETY: This macro has the exact same safety requirement as
@@ -657,6 +673,13 @@ macro_rules! impl_device_context_deref {
 #[doc(hidden)]
 #[macro_export]
 macro_rules! __impl_device_context_into_aref {
+    (<$lt:lifetime> $src:ty, $device:tt) => {
+        impl<$lt> ::core::convert::From<&$device<$src>> for $crate::sync::aref::ARef<$device> {
+            fn from(dev: &$device<$src>) -> Self {
+                (&**dev).into()
+            }
+        }
+    };
     ($src:ty, $device:tt) => {
         impl ::core::convert::From<&$device<$src>> for $crate::sync::aref::ARef<$device> {
             fn from(dev: &$device<$src>) -> Self {
@@ -671,8 +694,12 @@ macro_rules! __impl_device_context_into_aref {
 #[macro_export]
 macro_rules! impl_device_context_into_aref {
     ($device:tt) => {
-        ::kernel::__impl_device_context_into_aref!($crate::device::CoreInternal, $device);
-        ::kernel::__impl_device_context_into_aref!($crate::device::Core, $device);
+        ::kernel::__impl_device_context_into_aref!(
+            <'a> $crate::device::CoreInternal<'a>, $device
+        );
+        ::kernel::__impl_device_context_into_aref!(
+            <'a> $crate::device::Core<'a>, $device
+        );
         ::kernel::__impl_device_context_into_aref!($crate::device::Bound, $device);
     };
 }
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