linux-kernel - [PATCH 2/5] rust: device: Add a minimal RawDevice trait

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Message-Id: <20230224-rust-iopt-rtkit-v1-2-49ced3391295@asahilina.net>
Date:   Fri, 24 Feb 2023 19:53:14 +0900
From:   Asahi Lina <lina@...hilina.net>
To:     Miguel Ojeda <ojeda@...nel.org>,
        Alex Gaynor <alex.gaynor@...il.com>,
        Wedson Almeida Filho <wedsonaf@...il.com>,
        Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>,
        Björn Roy Baron <bjorn3_gh@...tonmail.com>,
        Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Joerg Roedel <joro@...tes.org>,
        Hector Martin <marcan@...can.st>,
        Sven Peter <sven@...npeter.dev>, Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Alyssa Rosenzweig <alyssa@...enzweig.io>,
        Neal Gompa <neal@...pa.dev>, rust-for-linux@...r.kernel.org,
        linux-kernel@...r.kernel.org, asahi@...ts.linux.dev,
        Asahi Lina <lina@...hilina.net>
Subject: [PATCH 2/5] rust: device: Add a minimal RawDevice trait

From: Wedson Almeida Filho <wedsonaf@...il.com>

Add a RawDevice trait which can be implemented by any type representing
a device class (such as a PlatformDevice). This is the minimum amount of
Device support code required to unblock abstractions that need to take
device pointers.

Lina: Rewrote commit message, and dropped everything except RawDevice.

Co-developed-by: Miguel Ojeda <ojeda@...nel.org>
Signed-off-by: Miguel Ojeda <ojeda@...nel.org>
Signed-off-by: Wedson Almeida Filho <wedsonaf@...il.com>
Signed-off-by: Asahi Lina <lina@...hilina.net>
---
 rust/bindings/bindings_helper.h |  1 +
 rust/kernel/device.rs           | 23 +++++++++++++++++++++++
 rust/kernel/lib.rs              |  1 +
 3 files changed, 25 insertions(+)

diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h
index 75d85bd6c592..3632a39a28a6 100644
--- a/rust/bindings/bindings_helper.h
+++ b/rust/bindings/bindings_helper.h
@@ -6,6 +6,7 @@
  * Sorted alphabetically.
  */
 
+#include <linux/device.h>
 #include <linux/slab.h>
 #include <linux/refcount.h>
 
diff --git a/rust/kernel/device.rs b/rust/kernel/device.rs
new file mode 100644
index 000000000000..9be021e393ca
--- /dev/null
+++ b/rust/kernel/device.rs
@@ -0,0 +1,23 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Generic devices that are part of the kernel's driver model.
+//!
+//! C header: [`include/linux/device.h`](../../../../include/linux/device.h)
+
+use crate::bindings;
+
+/// A raw device.
+///
+/// # Safety
+///
+/// Implementers must ensure that the `*mut device` returned by [`RawDevice::raw_device`] is
+/// related to `self`, that is, actions on it will affect `self`. For example, if one calls
+/// `get_device`, then the refcount on the device represented by `self` will be incremented.
+///
+/// Additionally, implementers must ensure that the device is never renamed. Commit a5462516aa99
+/// ("driver-core: document restrictions on device_rename()") has details on why `device_rename`
+/// should not be used.
+pub unsafe trait RawDevice {
+    /// Returns the raw `struct device` related to `self`.
+    fn raw_device(&self) -> *mut bindings::device;
+}
diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
index 82dff6f4cf60..de44092718f8 100644
--- a/rust/kernel/lib.rs
+++ b/rust/kernel/lib.rs
@@ -29,6 +29,7 @@ compile_error!("Missing kernel configuration for conditional compilation");
 #[cfg(not(testlib))]
 mod allocator;
 mod build_assert;
+pub mod device;
 pub mod error;
 pub mod prelude;
 pub mod print;

-- 
2.35.1