[PATCH 1/9] rust: device: implement impl_device_context_deref!

[Danilo Krummrich <dakr@kernel.org>]

The Deref hierarchy for device context generics is the same for every
(bus specific) device.

Implement those with a generic macro to avoid duplicated boiler plate
code and ensure the correct Deref hierarchy for every device
implementation.

Signed-off-by: Danilo Krummrich <dakr@kernel.org>
---
 rust/kernel/device.rs   | 29 +++++++++++++++++++++++++++++
 rust/kernel/pci.rs      | 14 +-------------
 rust/kernel/platform.rs | 15 +--------------
 3 files changed, 31 insertions(+), 27 deletions(-)

diff --git a/rust/kernel/device.rs b/rust/kernel/device.rs
index 21b343a1dc4d..e3ab8980270e 100644
--- a/rust/kernel/device.rs
+++ b/rust/kernel/device.rs
@@ -235,6 +235,35 @@ impl Sealed for super::Normal {}
 impl DeviceContext for Core {}
 impl DeviceContext for Normal {}
 
+#[doc(hidden)]
+#[macro_export]
+macro_rules! __impl_device_context_deref {
+    ($src:ty, $dst:ty, $device:tt) => {
+        impl core::ops::Deref for $device<$src> {
+            type Target = $device<$dst>;
+
+            fn deref(&self) -> &Self::Target {
+                let ptr: *const Self = self;
+
+                // CAST: `Device<Ctx: DeviceContext>` types are transparent to each other.
+                let ptr = ptr.cast::<Self::Target>();
+
+                // SAFETY: `ptr` was derived from `&self`.
+                unsafe { &*ptr }
+            }
+        }
+    };
+}
+
+/// Implement [`core::ops::Deref`] traits for allowed [`DeviceContext`] conversions of a (bus
+/// specific) device.
+#[macro_export]
+macro_rules! impl_device_context_deref {
+    ($device:tt) => {
+        kernel::__impl_device_context_deref!($crate::device::Core, $crate::device::Normal, $device);
+    };
+}
+
 #[doc(hidden)]
 #[macro_export]
 macro_rules! dev_printk {
diff --git a/rust/kernel/pci.rs b/rust/kernel/pci.rs
index c97d6d470b28..0e735409bfc4 100644
--- a/rust/kernel/pci.rs
+++ b/rust/kernel/pci.rs
@@ -422,19 +422,7 @@ pub fn set_master(&self) {
     }
 }
 
-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::pci_dev>`.
-        let ptr = ptr.cast::<Device>();
-
-        // SAFETY: `ptr` was derived from `&self`.
-        unsafe { &*ptr }
-    }
-}
+kernel::impl_device_context_deref!(Device);
 
 impl From<&Device<device::Core>> for ARef<Device> {
     fn from(dev: &Device<device::Core>) -> Self {
diff --git a/rust/kernel/platform.rs b/rust/kernel/platform.rs
index 4917cb34e2fe..9268e1edca9b 100644
--- a/rust/kernel/platform.rs
+++ b/rust/kernel/platform.rs
@@ -16,7 +16,6 @@
 
 use core::{
     marker::PhantomData,
-    ops::Deref,
     ptr::{addr_of_mut, NonNull},
 };
 
@@ -190,19 +189,7 @@ fn as_raw(&self) -> *mut bindings::platform_device {
     }
 }
 
-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 }
-    }
-}
+kernel::impl_device_context_deref!(Device);
 
 impl From<&Device<device::Core>> for ARef<Device> {
     fn from(dev: &Device<device::Core>) -> Self {
-- 
2.49.0