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Message-ID: <20251018205912.1528811-2-markus.probst@posteo.de>
Date: Sat, 18 Oct 2025 20:59:34 +0000
From: Markus Probst <markus.probst@...teo.de>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Miguel Ojeda <ojeda@...nel.org>,
Alex Gaynor <alex.gaynor@...il.com>,
Danilo Krummrich <dakr@...nel.org>,
"Rafael J. Wysocki" <rafael@...nel.org>,
Igor Korotin <igor.korotin.linux@...il.com>,
Lee Jones <lee@...nel.org>,
Pavel Machek <pavel@...nel.org>
Cc: Dave Ertman <david.m.ertman@...el.com>,
Ira Weiny <ira.weiny@...el.com>,
Leon Romanovsky <leon@...nel.org>,
Boqun Feng <boqun.feng@...il.com>,
Gary Guo <gary@...yguo.net>,
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>,
Daniel Almeida <daniel.almeida@...labora.com>,
Bjorn Helgaas <bhelgaas@...gle.com>,
kwilczynski@...nel.org,
linux-kernel@...r.kernel.org,
rust-for-linux@...r.kernel.org,
linux-pci@...r.kernel.org,
linux-leds@...r.kernel.org,
Markus Probst <markus.probst@...teo.de>
Subject: [PATCH v5 1/2] rust: Add trait to convert a device reference to a bus device reference
Implement the `IntoBusDevice` trait for converting a `Device` reference to a
bus device reference for all bus devices. `Device` implements this trait as a
fallback.
The `IntoBusDevice` trait allows abstractions to provide the bus device in
class device callbacks.
Signed-off-by: Markus Probst <markus.probst@...teo.de>
---
rust/kernel/auxiliary.rs | 7 +++++++
rust/kernel/device.rs | 41 ++++++++++++++++++++++++++++++++++++++++
rust/kernel/i2c.rs | 7 +++++++
rust/kernel/pci.rs | 7 +++++++
rust/kernel/usb.rs | 6 ++++++
5 files changed, 68 insertions(+)
diff --git a/rust/kernel/auxiliary.rs b/rust/kernel/auxiliary.rs
index e11848bbf206..dea24265f549 100644
--- a/rust/kernel/auxiliary.rs
+++ b/rust/kernel/auxiliary.rs
@@ -15,6 +15,7 @@
};
use core::{
marker::PhantomData,
+ mem::offset_of,
ptr::{addr_of_mut, NonNull},
};
@@ -239,6 +240,12 @@ extern "C" fn release(dev: *mut bindings::device) {
}
}
+// SAFETY: `auxilary::Device` is a transparent wrapper of `struct auxiliary_device`.
+// The offset is guaranteed to point to a valid device field inside `auxilary::Device`.
+unsafe impl<Ctx: device::DeviceContext> device::IntoBusDevice<Ctx> for Device<Ctx> {
+ const OFFSET: usize = offset_of!(bindings::auxiliary_device, dev);
+}
+
// SAFETY: `Device` is a transparent wrapper of a type that doesn't depend on `Device`'s generic
// argument.
kernel::impl_device_context_deref!(unsafe { Device });
diff --git a/rust/kernel/device.rs b/rust/kernel/device.rs
index 1321e6f0b53c..5527854a195f 100644
--- a/rust/kernel/device.rs
+++ b/rust/kernel/device.rs
@@ -511,6 +511,47 @@ impl DeviceContext for Core {}
impl DeviceContext for CoreInternal {}
impl DeviceContext for Normal {}
+/// Bus devices can implement this trait to allow abstractions to provide the bus device in
+/// class device callbacks.
+///
+/// # Safety
+///
+/// `IntoBusDevice::OFFSET` must be a offset to a device field in the implemented struct.
+pub(crate) unsafe trait IntoBusDevice<Ctx: DeviceContext>:
+ AsRef<Device<Ctx>>
+{
+ /// The relative offset to the device field.
+ ///
+ /// Use `offset_of!(bindings, field)` macro to avoid breakage.
+ const OFFSET: usize;
+
+ /// Convert a reference to [`Device`] into `Self`.
+ ///
+ /// # Safety
+ ///
+ /// `dev` must be contained in `Self`.
+ unsafe fn from_device(dev: &Device<Ctx>) -> &Self
+ where
+ Self: Sized,
+ {
+ let raw = dev.as_raw();
+ // SAFETY: `raw - Self::OFFSET` is guaranteed by the safety requirements
+ // to be a valid pointer to `Self`.
+ unsafe { &*raw.byte_sub(Self::OFFSET).cast::<Self>() }
+ }
+}
+
+// SAFETY: `Device` is a transparent wrapper of `device`.
+unsafe impl<Ctx: DeviceContext> IntoBusDevice<Ctx> for Device<Ctx> {
+ const OFFSET: usize = 0;
+}
+
+impl<Ctx: DeviceContext> AsRef<Device<Ctx>> for Device<Ctx> {
+ fn as_ref(&self) -> &Device<Ctx> {
+ self
+ }
+}
+
/// # Safety
///
/// The type given as `$device` must be a transparent wrapper of a type that doesn't depend on the
diff --git a/rust/kernel/i2c.rs b/rust/kernel/i2c.rs
index 7fccffebbd6c..e9a7e09b0116 100644
--- a/rust/kernel/i2c.rs
+++ b/rust/kernel/i2c.rs
@@ -15,6 +15,7 @@
use core::{
marker::PhantomData,
+ mem::offset_of,
ptr::{from_ref, NonNull},
};
@@ -465,6 +466,12 @@ fn as_raw(&self) -> *mut bindings::i2c_client {
}
}
+// SAFETY: `I2cClient` is a transparent wrapper of `struct i2c_client`.
+// The offset is guaranteed to point to a valid device field inside `I2cClient`.
+unsafe impl<Ctx: device::DeviceContext> device::IntoBusDevice<Ctx> for I2cClient<Ctx> {
+ const OFFSET: usize = offset_of!(bindings::i2c_client, dev);
+}
+
// SAFETY: `I2cClient` is a transparent wrapper of a type that doesn't depend on `I2cClient`'s generic
// argument.
kernel::impl_device_context_deref!(unsafe { I2cClient });
diff --git a/rust/kernel/pci.rs b/rust/kernel/pci.rs
index 7fcc5f6022c1..ad00a5c1294a 100644
--- a/rust/kernel/pci.rs
+++ b/rust/kernel/pci.rs
@@ -19,6 +19,7 @@
};
use core::{
marker::PhantomData,
+ mem::offset_of,
ops::Deref,
ptr::{addr_of_mut, NonNull},
};
@@ -593,6 +594,12 @@ pub fn set_master(&self) {
}
}
+// SAFETY: `pci::Device` is a transparent wrapper of `struct pci_dev`.
+// The offset is guaranteed to point to a valid device field inside `pci::Device`.
+unsafe impl<Ctx: device::DeviceContext> device::IntoBusDevice<Ctx> for Device<Ctx> {
+ const OFFSET: usize = offset_of!(bindings::pci_dev, dev);
+}
+
// SAFETY: `Device` is a transparent wrapper of a type that doesn't depend on `Device`'s generic
// argument.
kernel::impl_device_context_deref!(unsafe { Device });
diff --git a/rust/kernel/usb.rs b/rust/kernel/usb.rs
index 14ddb711bab3..8862004e54f9 100644
--- a/rust/kernel/usb.rs
+++ b/rust/kernel/usb.rs
@@ -324,6 +324,12 @@ fn as_raw(&self) -> *mut bindings::usb_interface {
}
}
+// SAFETY: `usb::Interface` is a transparent wrapper of `struct usb_interface`.
+// The offset is guaranteed to point to a valid device field inside `usb::Interface`.
+unsafe impl<Ctx: device::DeviceContext> device::IntoBusDevice<Ctx> for Interface<Ctx> {
+ const OFFSET: usize = offset_of!(bindings::usb_interface, dev);
+}
+
// SAFETY: `Interface` is a transparent wrapper of a type that doesn't depend on
// `Interface`'s generic argument.
kernel::impl_device_context_deref!(unsafe { Interface });
--
2.49.1
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