linux-kernel - [PATCH] rust: device: add platdata accessors

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Message-Id: <20260108085545.333676-1-pengfuyuan@kylinos.cn>
Date: Thu,  8 Jan 2026 16:55:45 +0800
From: pengfuyuan <pengfuyuan@...inos.cn>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: "Rafael J . Wysocki" <rafael@...nel.org>,
	Danilo Krummrich <dakr@...nel.org>,
	Miguel Ojeda <ojeda@...nel.org>,
	Boqun Feng <boqun.feng@...il.com>,
	Gary Guo <gary@...yguo.net>,
	Björn Roy Baron <bjorn3_gh@...tonmail.com>,
	Benno Lossin <lossin@...nel.org>,
	Andreas Hindborg <a.hindborg@...nel.org>,
	Alice Ryhl <aliceryhl@...gle.com>,
	Trevor Gross <tmgross@...ch.edu>,
	rust-for-linux@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	pengfuyuan <pengfuyuan@...inos.cn>
Subject: [PATCH] rust: device: add platdata accessors

Implement generic accessors for the platform data of a device.

Platform data is typically set by platform code when creating the device
and points to platform-specific data structures. The accessor provides
type-safe access to this data without requiring unsafe code at the call
site.

The accessor is implemented for Device<Bound>, allowing drivers to access
platform data during probe() and other device lifecycle callbacks. Unlike
drvdata, platform data is managed by platform code and has a lifetime
tied to the device itself.

Signed-off-by: pengfuyuan <pengfuyuan@...inos.cn>
---
 rust/kernel/device.rs | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/rust/kernel/device.rs b/rust/kernel/device.rs
index c79be2e2bfe3..e16f8eaa52e0 100644
--- a/rust/kernel/device.rs
+++ b/rust/kernel/device.rs
@@ -325,6 +325,31 @@ pub fn drvdata<T: 'static>(&self) -> Result<Pin<&T>> {
         // - We've just checked that the type of the driver's private data is in fact `T`.
         Ok(unsafe { self.drvdata_unchecked() })
     }
+
+    /// Access the platform data for this device.
+    ///
+    /// The lifetime of the platform data is tied to the device's lifetime.
+    /// Returns a reference to the platform data of type `T`, or [`ENOENT`] if no platform data
+    /// is set.
+    ///
+    /// # Type Safety
+    ///
+    /// This function does not perform runtime type checking. The caller must ensure that the
+    /// platform data structure actually matches the type `T` for the specific platform device.
+    /// Incorrect type usage will result in undefined behavior.
+    pub fn platdata<T>(&self) -> Result<&T> {
+        // SAFETY: By the type invariants, `self.as_raw()` is a valid pointer to a `struct device`.
+        let ptr = unsafe { (*self.as_raw()).platform_data };
+
+        if ptr.is_null() {
+            return Err(ENOENT);
+        }
+
+        // SAFETY:
+        // - `ptr` is not null, so it points to valid memory.
+        // - The caller must ensure that the platform data structure matches type `T`.
+        Ok(unsafe { &*ptr.cast::<T>() })
+    }
 }
 
 impl<Ctx: DeviceContext> Device<Ctx> {
-- 
2.25.1