From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 5ADA43A6B81; Mon, 27 Apr 2026 22:12:08 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777327928; cv=none; b=kRHGdOhG3yLOlFvJ0sStknNUPVzXWtI4CAmoF4p7fPta1qlH8q0nr2aGQViq3UjdGMxZMOe2lNUocT8OU4I7xlB0ifV7IG4Cz9B9PImX78kWguAbVHBjoePbPvJkBvn+Cb2MYvnb4YBNX+3V+9FeUDUbQ0oNgaXAOE14hOVJ1Wg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777327928; c=relaxed/simple; bh=0thXPdShB3t5adcBz1VkWyZ33OoOiYeBGZx1pE9VSCE=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=bcIrznXy4Fbv2wVTXg02DT8cUU+DXiZC0ovZh5hNFr1z4eWUdqG8224FAxlUnorx1Q1lOTLUN+UYCPKupe3aXGbD5vMAkpgrkZrCpHFxrNfkoFSQtAa/f0Y21Igvabg/M4viNv3b2C1oDp6AEC2b22Jfw30w02mq6eSA/XMtKXc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Z7nbSyXy; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Z7nbSyXy" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 49D48C19425; Mon, 27 Apr 2026 22:12:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1777327928; bh=0thXPdShB3t5adcBz1VkWyZ33OoOiYeBGZx1pE9VSCE=; h=From:To:Cc:Subject:Date:From; b=Z7nbSyXy34HFoImwriB49Cku0ZZoA0kXlQ6jBhSYj9BVkWR7Sn4VlBPH3sZXjPE2g m8dDBnZVc9okYF8//vnRWpYKv+KYnEwt15cL/SiYb52pls2wZlLE6lBEIOl45Mx5Zj HRBPuaBrspJtiVYckLKyxs3+F3dl5L819mk1eokoINgUZkq37Ca5e6nGwXM1KvaqrB 7UqWXRUUhhm5V/a0HyxMqqjubV2YBMvL81XPNZ/piO9nWLFwyVjwUYT6PwzsLsNTbz HUtlrVffhg+N9YbCvVgdnQVM5Tpznoon8co4YJxeDtDTMw9z6O2kfn/XUXwQMiPp00 I2RG39QWsSeoA== From: Danilo Krummrich To: gregkh@linuxfoundation.org, rafael@kernel.org, acourbot@nvidia.com, aliceryhl@google.com, david.m.ertman@intel.com, ira.weiny@intel.com, leon@kernel.org, viresh.kumar@linaro.org, m.wilczynski@samsung.com, ukleinek@kernel.org, bhelgaas@google.com, kwilczynski@kernel.org, abdiel.janulgue@gmail.com, robin.murphy@arm.com, markus.probst@posteo.de, ojeda@kernel.org, boqun@kernel.org, gary@garyguo.net, bjorn3_gh@protonmail.com, lossin@kernel.org, a.hindborg@kernel.org, tmgross@umich.edu Cc: driver-core@lists.linux.dev, linux-kernel@vger.kernel.org, nova-gpu@lists.linux.dev, dri-devel@lists.freedesktop.org, linux-pm@vger.kernel.org, linux-pwm@vger.kernel.org, linux-pci@vger.kernel.org, rust-for-linux@vger.kernel.org, Danilo Krummrich Subject: [PATCH 00/24] rust: device: Higher-Ranked Lifetime Types for device drivers Date: Tue, 28 Apr 2026 00:10:58 +0200 Message-ID: <20260427221155.2144848-1-dakr@kernel.org> X-Mailer: git-send-email 2.54.0 Precedence: bulk X-Mailing-List: rust-for-linux@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Currently, Rust device drivers access device resources such as PCI BAR mappings and I/O memory regions through Devres. Devres::access() provides zero-overhead access by taking a &Device reference as proof that the device is still bound. Since a &Device is available in almost all contexts by design, Devres is mostly a type-system level proof that the resource is valid, but it can also be used from scopes without this guarantee through its try_access() accessor. This works well in general, but has a few limitations: - Every access to a device resource goes through Devres::access(), which despite zero cost, adds boilerplate to every access site. - Destructors do not receive a &Device, so they must use try_access(), which can fail. In practice the access succeeds if teardown ordering is correct, but the type system can't express this, forcing drivers to handle a failure path that should never be taken. - Sharing a resource across components (e.g. passing a BAR to a sub-component) requires Arc>. - Device references must be stored as ARef rather than plain &Device borrows. These limitations stem from the driver's bus device private data being 'static -- the driver struct cannot borrow from the device reference it receives in probe(), even though it structurally cannot outlive the device binding. This series introduces Higher-Ranked Lifetime Types (HRT) for Rust device drivers. An HRT is a type that is generic over a lifetime -- it does not have a fixed lifetime, but can be instantiated with any lifetime chosen by the caller. Rust does not directly support types that are generic over a lifetime as type parameters; the ForLt trait (contributed by Gary Guo) encodes this internally. The module_*_driver! macros handle the wrapping, so driver authors just write struct MyDriver<'a> and impl Driver<'a>. With HRT, driver structs carry a lifetime parameter tied to the device binding scope -- the interval of a bus device being bound to a driver. Device resources like pci::Bar<'a> and IoMem<'a> are handed out with this lifetime, so the compiler enforces at build time that they do not escape the binding scope. Before: struct MyDriver { pdev: ARef, bar: Devres>, } let io = self.bar.access(dev)?; io.read32(OFFSET); After: struct MyDriver<'a> { pdev: &'a pci::Device, bar: pci::Bar<'a, BAR_SIZE>, } self.bar.read32(OFFSET); Lifetime-parameterized device resources can be put into a Devres at any point via Bar::into_devres() / IoMem::into_devres(), providing the exact same semantics as before. This is useful for resources shared across subsystem boundaries where revocation is needed. This also synergizes with the upcoming self-referential initialization support in pin-init, which allows one field of the driver struct to borrow another during initialization without unsafe code. The same pattern is applied to auxiliary device registration data as a first example beyond bus device private data. Registration can hold lifetime-parameterized data tied to the parent driver's binding scope. Since the auxiliary bus guarantees that the parent remains bound while the auxiliary device is registered, the registration data can safely borrow the parent's device resources. More generally, binding resource lifetimes to a registration scope applies to every registration that is scoped to a driver binding -- auxiliary devices, class devices, IRQ handlers, workqueues. A follow-up series extends this to class device registrations, starting with DRM, so that class device callbacks (IOCTLs, etc.) can safely access device resources through the separate registration data bound to the registration's lifetime without Devres indirection. The series contains a few driver patches for reference, indicated by the REF suffix. Thanks to Gary for coming up with the ForLt implementation; thanks to Alice for the early discussions around lifetime-parameterized private data that helped shape the direction of this work. This series depends on [1]. [1] https://lore.kernel.org/driver-core/20260427221002.2143861-1-dakr@kernel.org/ Danilo Krummrich (23): rust: driver core: drop drvdata before devres release rust: devres: add ForLt support to Devres rust: device: generalize drvdata methods over ForLt rust: driver: make Adapter trait lifetime-parameterized rust: pci: implement Sync for Device rust: platform: implement Sync for Device rust: auxiliary: implement Sync for Device rust: usb: implement Sync for Device rust: device: implement Sync for Device rust: pci: make Driver trait lifetime-parameterized rust: platform: make Driver trait lifetime-parameterized rust: auxiliary: make Driver trait lifetime-parameterized rust: auxiliary: generalize Registration over ForLt samples: rust: rust_driver_auxiliary: showcase lifetime-bound registration data rust: usb: make Driver trait lifetime-parameterized rust: i2c: make Driver trait lifetime-parameterized rust: pci: make Bar lifetime-parameterized rust: io: make IoMem and ExclusiveIoMem lifetime-parameterized samples: rust: rust_driver_pci: use HRT lifetime for Bar gpu: nova-core: use HRT lifetime for Bar gpu: nova-core: unregister sysmem flush page from Drop gpu: nova-core: replace ARef with &'a Device in SysmemFlush gpu: drm: tyr: use HRT lifetime for IoMem Gary Guo (1): rust: types: add `ForLt` trait for higher-ranked lifetime support drivers/base/dd.c | 2 +- drivers/cpufreq/rcpufreq_dt.rs | 10 +- drivers/gpu/drm/nova/driver.rs | 9 +- drivers/gpu/drm/tyr/driver.rs | 24 ++- drivers/gpu/drm/tyr/gpu.rs | 62 ++++--- drivers/gpu/drm/tyr/regs.rs | 21 +-- drivers/gpu/nova-core/driver.rs | 48 ++--- drivers/gpu/nova-core/fb.rs | 31 ++-- drivers/gpu/nova-core/gpu.rs | 32 +--- drivers/gpu/nova-core/nova_core.rs | 4 +- drivers/pwm/pwm_th1520.rs | 14 +- include/linux/device/driver.h | 4 +- rust/Makefile | 1 + rust/kernel/auxiliary.rs | 144 ++++++++++----- rust/kernel/cpufreq.rs | 8 +- rust/kernel/device.rs | 84 ++++++--- rust/kernel/devres.rs | 31 +++- rust/kernel/driver.rs | 44 +++-- rust/kernel/i2c.rs | 121 ++++++++----- rust/kernel/io/mem.rs | 118 ++++++------- rust/kernel/pci.rs | 88 +++++++--- rust/kernel/pci/io.rs | 50 +++--- rust/kernel/platform.rs | 101 +++++++---- rust/kernel/types.rs | 4 + rust/kernel/types/for_lt.rs | 117 +++++++++++++ rust/kernel/usb.rs | 93 ++++++---- rust/macros/for_lt.rs | 242 ++++++++++++++++++++++++++ rust/macros/lib.rs | 12 ++ samples/rust/rust_debugfs.rs | 10 +- samples/rust/rust_dma.rs | 9 +- samples/rust/rust_driver_auxiliary.rs | 53 ++++-- samples/rust/rust_driver_i2c.rs | 18 +- samples/rust/rust_driver_pci.rs | 93 +++++----- samples/rust/rust_driver_platform.rs | 12 +- samples/rust/rust_driver_usb.rs | 14 +- samples/rust/rust_i2c_client.rs | 12 +- samples/rust/rust_soc.rs | 12 +- 37 files changed, 1182 insertions(+), 570 deletions(-) create mode 100644 rust/kernel/types/for_lt.rs create mode 100644 rust/macros/for_lt.rs -- 2.54.0