Merge tag 'topic/device-context-2025-04-17' into nova-next

Introduce "Bound" device context

Introduce the "Bound" device context, such that it can be ensured to only
ever pass a bound device to APIs that require this precondition. [1]

This tag exists to share the patches from [1] between multiple trees.

[1] https://lore.kernel.org/lkml/20250413173758.12068-1-dakr@kernel.org/

1 files changed, 8 insertions, 24 deletions

diff --git a/rust/kernel/platform.rs b/rust/kernel/platform.rs
index 4917cb34e2fe..b1c48cd95cd6 100644
--- a/rust/kernel/platform.rs
+++ b/rust/kernel/platform.rs
@@ -10,13 +10,12 @@ use crate::{
     of,
     prelude::*,
     str::CStr,
-    types::{ARef, ForeignOwnable, Opaque},
+    types::{ForeignOwnable, Opaque},
     ThisModule,
 };
 
 use core::{
     marker::PhantomData,
-    ops::Deref,
     ptr::{addr_of_mut, NonNull},
 };
 
@@ -184,31 +183,16 @@ pub struct Device<Ctx: device::DeviceContext = device::Normal>(
     PhantomData<Ctx>,
 );
 
-impl Device {
+impl<Ctx: device::DeviceContext> Device<Ctx> {
     fn as_raw(&self) -> *mut bindings::platform_device {
         self.0.get()
     }
 }
 
-impl Deref for Device<device::Core> {
-    type Target = Device;
-
-    fn deref(&self) -> &Self::Target {
-        let ptr: *const Self = self;
-
-        // CAST: `Device<Ctx>` is a transparent wrapper of `Opaque<bindings::platform_device>`.
-        let ptr = ptr.cast::<Device>();
-
-        // SAFETY: `ptr` was derived from `&self`.
-        unsafe { &*ptr }
-    }
-}
-
-impl From<&Device<device::Core>> for ARef<Device> {
-    fn from(dev: &Device<device::Core>) -> Self {
-        (&**dev).into()
-    }
-}
+// SAFETY: `Device` is a transparent wrapper of a type that doesn't depend on `Device`'s generic
+// argument.
+kernel::impl_device_context_deref!(unsafe { Device });
+kernel::impl_device_context_into_aref!(Device);
 
 // SAFETY: Instances of `Device` are always reference-counted.
 unsafe impl crate::types::AlwaysRefCounted for Device {
@@ -223,8 +207,8 @@ unsafe impl crate::types::AlwaysRefCounted for Device {
     }
 }
 
-impl AsRef<device::Device> for Device {
-    fn as_ref(&self) -> &device::Device {
+impl<Ctx: device::DeviceContext> AsRef<device::Device<Ctx>> for Device<Ctx> {
+    fn as_ref(&self) -> &device::Device<Ctx> {
         // SAFETY: By the type invariant of `Self`, `self.as_raw()` is a pointer to a valid
         // `struct platform_device`.
         let dev = unsafe { addr_of_mut!((*self.as_raw()).dev) };