From nobody Sat Feb 7 08:28:36 2026 Received: from mout02.posteo.de (mout02.posteo.de [185.67.36.66]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4632727A103 for ; Sat, 18 Oct 2025 20:59:43 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=185.67.36.66 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760821186; cv=none; b=DvBvs0vVB2ufce9AO/H1wqCvSKOS8XTjcpLdfQ9nCes+KzVwFAznwYjD+11K2m7kkjV02gk+P0VT0n0ZSsms6uSueHraah3TdH4X5d23MauBwEpzbFpN3EqxvbvzOtUHfxY+2gADDPVrZqmzErClIWvF9zzVvL2U5vT9IZm0Be4= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760821186; c=relaxed/simple; bh=RCcTbaW5Rz4zsoAlDMcqww/CGBu4BzS0JbMOr6YEZHw=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=UMYaFFTwOqmbkuxWvQi2NvbXxp5SD+bTLhayz1RVijsapWVD3m/kQUKXSZMtiXXGuti9xVgfHwoo2QP+17WdiZyHBEgCt0OVfdrTY0ykFtMiDz2Iengrdmz48pDVIrgqhp9B332BiT+3hYwL2LdOnf8BUuIHLEngIBJrM+dv4cM= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=posteo.de; spf=pass smtp.mailfrom=posteo.de; dkim=pass (2048-bit key) header.d=posteo.de header.i=@posteo.de header.b=gYOQXG41; arc=none smtp.client-ip=185.67.36.66 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=posteo.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=posteo.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=posteo.de header.i=@posteo.de header.b="gYOQXG41" Received: from submission (posteo.de [185.67.36.169]) by mout02.posteo.de (Postfix) with ESMTPS id E2E84240103 for ; Sat, 18 Oct 2025 22:59:35 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=posteo.de; s=2017; t=1760821175; bh=tZ+zmJaTSj3qqf88WH9BVovPMXRtbf3v8h9Fl8nwR98=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version: Content-Transfer-Encoding:Autocrypt:OpenPGP:From; b=gYOQXG41qFBz1ZqqNEEPwV+2647xcCwuatEmhx0l6/krd4Nc9zaifWywMjS/LZA4y 7+7ryMp76bqvzJfo7uEdniVD5s0b1KfDgkU1GctH8DunmZ8TDFQ2My7QbXcwAj743c mGjdgwara1I/GqAO8/jHgt5BIqx3mgHeApkfYR0EmwuMjmrhGMiRjgZ8bsA1XdopJ4 CNxntJm8pw4oh1nh2OIJCFBP5tK0WZofWKK4O+2QEoisbuA1YM0/4OIgLbB1zburBG gLnq5gGI3k5ISXqpiDplt3rnIZLMpDdUzBogGTr9qTqLy3q5pW3Xd+aNU8lzyto9DC zqlQgK1OAZT1w== Received: from customer (localhost [127.0.0.1]) by submission (posteo.de) with ESMTPSA id 4cpvFc5J87z9rxL; Sat, 18 Oct 2025 22:59:32 +0200 (CEST) From: Markus Probst To: Greg Kroah-Hartman , Miguel Ojeda , Alex Gaynor , Danilo Krummrich , "Rafael J. Wysocki" , Igor Korotin , Lee Jones , Pavel Machek Cc: Dave Ertman , Ira Weiny , Leon Romanovsky , Boqun Feng , Gary Guo , bjorn3_gh@protonmail.com, Benno Lossin , Andreas Hindborg , Alice Ryhl , Trevor Gross , Daniel Almeida , Bjorn Helgaas , kwilczynski@kernel.org, linux-kernel@vger.kernel.org, rust-for-linux@vger.kernel.org, linux-pci@vger.kernel.org, linux-leds@vger.kernel.org, Markus Probst Subject: [PATCH v5 1/2] rust: Add trait to convert a device reference to a bus device reference Date: Sat, 18 Oct 2025 20:59:34 +0000 Message-ID: <20251018205912.1528811-2-markus.probst@posteo.de> In-Reply-To: <20251018205912.1528811-1-markus.probst@posteo.de> References: <20251018205912.1528811-1-markus.probst@posteo.de> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=5668; i=markus.probst@posteo.de; h=from:subject; bh=RCcTbaW5Rz4zsoAlDMcqww/CGBu4BzS0JbMOr6YEZHw=; b=owEBbQKS/ZANAwAIATR2H/jnrUPSAcsmYgBo8/8fuK+NIKTy0f4Yc+4njfTXvlqhfKC/Krpww brGyFFrrhCJAjMEAAEIAB0WIQSCdBjE9KxY53IwxHM0dh/4561D0gUCaPP/HwAKCRA0dh/4561D 0nYKD/oCwKQL8li5QThDheIv4cXSIQQltV2JhePWcNT5DVILCeB9HGI1fSl4A5am0hdmWJ0k0Ju LSwtLJbgbGNae0CqIK2Cu1ITAdpddLCDVCKvMBx9K4d1zatgJcX9pGSz7zxBtL/9OheEqb/otsN 1sW9H+cnWbIzGFqOMfaUyF+c6TBTIO/Tb/LblhFg1E30r7G87sMOGe7RMtZ86JAb5/bZhIlXLTe HTwRFB7ULDRC9m6v2fi93fH26x+yew0VRFx4FaavlXi/gNL5pbc0bxdIwpepXbnwQCYUe7W9t34 vBV0kj5FkZ0GJY5kaCj7tTuqpJ/KWDIBT4IombkfByMORrSkm6Hi5x7YLeaPlviTInnhR9zv3dc 2IjmnZncC0+nKzogoNVOkhe2sfgu97xIah1p87sSrqjrrLAlXshbl6OIbMogXympu1WA/U6kLIj 0CT7zXb+hNXaPsNoIZ++7xOWB4fnBLnJevV3gncRxfKH1qOm5Np0LkcgZks1CWj+Riu8lH5gpnp tzCYrEuOsN14ZsEsrc85CRoJUrtbcXFhLi8pC/sgHyph+LnZfjwQeRfbuhAwL9oFg0gL0wQBg5t pdpdJnFxaA5ELZH+2LU8JFpNYy5wQhmSiOxv41kc46GFdQze3/OOkc56k7zbOo2vbDdso28L83o WIhmfzkuf/Y/NCA= = X-Developer-Key: i=markus.probst@posteo.de; 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preference=encrypt Content-Type: text/plain; charset="utf-8" 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 --- 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}, }; =20 @@ -239,6 +240,12 @@ extern "C" fn release(dev: *mut bindings::device) { } } =20 +// SAFETY: `auxilary::Device` is a transparent wrapper of `struct auxiliar= y_device`. +// The offset is guaranteed to point to a valid device field inside `auxil= ary::Device`. +unsafe impl device::IntoBusDevice for Dev= ice { + const OFFSET: usize =3D 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 {} =20 +/// 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 impl= emented struct. +pub(crate) unsafe trait IntoBusDevice: + AsRef> +{ + /// 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) -> &Self + where + Self: Sized, + { + let raw =3D dev.as_raw(); + // SAFETY: `raw - Self::OFFSET` is guaranteed by the safety requir= ements + // to be a valid pointer to `Self`. + unsafe { &*raw.byte_sub(Self::OFFSET).cast::() } + } +} + +// SAFETY: `Device` is a transparent wrapper of `device`. +unsafe impl IntoBusDevice for Device { + const OFFSET: usize =3D 0; +} + +impl AsRef> for Device { + fn as_ref(&self) -> &Device { + self + } +} + /// # Safety /// /// The type given as `$device` must be a transparent wrapper of a type th= at 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 @@ =20 use core::{ marker::PhantomData, + mem::offset_of, ptr::{from_ref, NonNull}, }; =20 @@ -465,6 +466,12 @@ fn as_raw(&self) -> *mut bindings::i2c_client { } } =20 +// SAFETY: `I2cClient` is a transparent wrapper of `struct i2c_client`. +// The offset is guaranteed to point to a valid device field inside `I2cCl= ient`. +unsafe impl device::IntoBusDevice for I2c= Client { + const OFFSET: usize =3D offset_of!(bindings::i2c_client, dev); +} + // SAFETY: `I2cClient` is a transparent wrapper of a type that doesn't dep= end 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) { } } =20 +// 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 device::IntoBusDevice for Dev= ice { + const OFFSET: usize =3D 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 { } } =20 +// SAFETY: `usb::Interface` is a transparent wrapper of `struct usb_interf= ace`. +// The offset is guaranteed to point to a valid device field inside `usb::= Interface`. +unsafe impl device::IntoBusDevice for Int= erface { + const OFFSET: usize =3D offset_of!(bindings::usb_interface, dev); +} + // SAFETY: `Interface` is a transparent wrapper of a type that doesn't dep= end on // `Interface`'s generic argument. kernel::impl_device_context_deref!(unsafe { Interface }); --=20 2.49.1