[RFC PATCH 7/8] rust: add firmware abstractions

[FUJITA Tomonori]

Hi,

On Fri, 31 May 2024 11:59:47 +0200
Danilo Krummrich <dakr at redhat.com> wrote:

> Once we get to a conclusion I can send a series with only the device and firmare
> abstractions such that we can get them in outside of the scope of the reset of
> both series to get your driver going.

Since your discussion with Greg seems to continue for a while, let me
include the following patch that Greg approved with the next version
of the PHY driver patchset.

You have the new version of the firmware patch? The unused functions
will not be merged so only request_firmware() and release_firmware()
can be included. If not, I can include my firmware patch that I wrote
before.

=
From: Danilo Krummrich <dakr at redhat.com>
Date: Fri, 7 Jun 2024 20:14:59 +0900
Subject: [PATCH] add abstraction for struct device

Add abstraction for struct device. This implements only the minimum
necessary functions required for the abstractions of firmware API;
that is, wrapping C's pointer to a device object with Rust struct only
during a caller knows the pointer is valid (e.g., the probe callback).

Co-developed-by: Wedson Almeida Filho <wedsonaf at gmail.com>
Signed-off-by: Wedson Almeida Filho <wedsonaf at gmail.com>
Signed-off-by: Danilo Krummrich <dakr at redhat.com>
Co-developed-by: FUJITA Tomonori <fujita.tomonori at gmail.com>
Signed-off-by: FUJITA Tomonori <fujita.tomonori at gmail.com>
Acked-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
---
 rust/kernel/device.rs | 31 +++++++++++++++++++++++++++++++
 rust/kernel/lib.rs    |  1 +
 2 files changed, 32 insertions(+)
 create mode 100644 rust/kernel/device.rs

diff --git a/rust/kernel/device.rs b/rust/kernel/device.rs
new file mode 100644
index 000000000000..55ec4f364628
--- /dev/null
+++ b/rust/kernel/device.rs
@@ -0,0 +1,31 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Generic devices that are part of the kernel's driver model.
+//!
+//! C header: [`include/linux/device.h`](srctree/include/linux/device.h)
+
+use crate::types::Opaque;
+
+/// Wraps the kernel's `struct task_struct`.
+#[repr(transparent)]
+pub struct Device(Opaque<bindings::device>);
+
+impl Device {
+    /// Creates a new [`Device`] instance from a raw pointer.
+    ///
+    /// # Safety
+    ///
+    /// For the duration of 'a, the pointer must point at a valid `device`.
+    pub unsafe fn from_raw<'a>(ptr: *mut bindings::device) -> &'a Self {
+        // CAST: `Self` is a `repr(transparent)` wrapper around `bindings::device`.
+        let ptr = ptr.cast::<Self>();
+        // SAFETY: by the function requirements the pointer is valid and we have unique access for
+        // the duration of `'a`.
+        unsafe { &mut *ptr }
+    }
+
+    /// Returns the raw pointer to the device.
+    pub(crate) fn as_raw(&self) -> *mut bindings::device {
+        self.0.get()
+    }
+}
diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
index fbd91a48ff8b..dd1207f1a873 100644
--- a/rust/kernel/lib.rs
+++ b/rust/kernel/lib.rs
@@ -28,6 +28,7 @@
 
 pub mod alloc;
 mod build_assert;
+pub mod device;
 pub mod error;
 pub mod init;
 pub mod ioctl;
-- 
2.34.1