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

[Asahi Lina <lina@asahilina.net>]

From: Wedson Almeida Filho <wedsonaf@gmail.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@kernel.org>
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
Signed-off-by: Wedson Almeida Filho <wedsonaf@gmail.com>
Signed-off-by: Asahi Lina <lina@asahilina.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