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 9338B3246E8; Wed, 6 May 2026 22:00:40 +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=1778104840; cv=none; b=IoU2ZUWt7MNkImAelXx+LjUEdrs2p/sdbo58ChcxFl6pO6NJ3sbdS423A29T63H9OysfS7k/fYha3TTjaGeWpokXnrlCLsIn/EP6qA+YV51IrNmI/VMNVa08TOHkvtmtUXiXtJec2PdOjvJOSIXY9UlOwbcLFyni88/EDwYiTvs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778104840; c=relaxed/simple; bh=qO/bJBZKk+2JX7D64j+KbHrwyxEIaJ1JMMkQoGp2JnE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=AwlbKQSuZ6hlxxqDUparSi1iNAnfaY50XUEZAo8c9sXGuys8aaT9089fmP29FLpZ+FiCtmuULildyDaDtbAIf1F6/C7+oF6ZhrUW2aDYB6f+8ysX0Dp9K4ipR4/NM0FYYJyKrIYJVQwwBYCHAtCfHjxWcWoAxci/aQiz9QaVBcM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=P7ypO5dF; 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="P7ypO5dF" Received: by smtp.kernel.org (Postfix) with ESMTPSA id F3676C2BCB0; Wed, 6 May 2026 22:00:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1778104840; bh=qO/bJBZKk+2JX7D64j+KbHrwyxEIaJ1JMMkQoGp2JnE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=P7ypO5dF3L0fBPUCnrrx6TaZenXdgGdQI7+zaewT/iX4gvhZQjbi/XtNoCeKZGSdp huZTtbG64v0FWXWbZqF45iaz77BzK7ymtNMEbsAam7fMkVTTi590vuR1SYKcr4IZoT LtPXr/16xMMQ6Ee7UQPHF2uxcwm/IMrHSnmz5pA4qJDWbApFw9ebqWXZMFUyqUI1Xy dXpKeIBIuj8GTQTqGl74bxNio3acLhxMfT5MBBtmatHZgJEtibHlvuD5eupsft6FEK wznkGnE7WBuXVotsYr+B5d73GxxhmeSldbnQtSNhWirZhDrHARwyBKrYe3GE5sAkm9 PcwXFCeFvZANQ== 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, igor.korotin@linux.dev, daniel.almeida@collabora.com 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 1/3] rust: devres: add DevresLt for ForLt-aware device resource access Date: Wed, 6 May 2026 23:58:33 +0200 Message-ID: <20260506220012.855173-2-dakr@kernel.org> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260506220012.855173-1-dakr@kernel.org> References: <20260506220012.855173-1-dakr@kernel.org> Precedence: bulk X-Mailing-List: linux-pm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Devres stores resources as T and returns &'bound T from access(). For lifetime-parameterized types like Bar<'bound, SIZE> that are transmuted to 'static for storage, this exposes the synthetic 'static lifetime to callers -- any method on the stored type that returns a reference with its lifetime parameter would yield a &'static reference, which is unsound. Add DevresLt, a thin wrapper around Devres> that applies ForLt::cast_ref in all access methods to shorten the stored 'static lifetime to the caller's borrow lifetime. Devres remains unchanged for static resource types. Signed-off-by: Danilo Krummrich --- rust/kernel/devres.rs | 97 +++++++++++++++++++++++++++++++++++++++---- 1 file changed, 90 insertions(+), 7 deletions(-) diff --git a/rust/kernel/devres.rs b/rust/kernel/devres.rs index 58efe80474bd..c9c698901871 100644 --- a/rust/kernel/devres.rs +++ b/rust/kernel/devres.rs @@ -24,6 +24,7 @@ Arc, // }, types::{ + ForLt, ForeignOwnable, Opaque, // }, @@ -122,7 +123,7 @@ struct Inner { /// # Ok(()) /// # } /// ``` -pub struct Devres { +pub struct Devres { dev: ARef, inner: Arc>, } @@ -184,7 +185,7 @@ pub(super) unsafe fn devres_node_remove( } } -impl Devres { +impl Devres { /// Creates a new [`Devres`] instance of the given `data`. /// /// The `data` encapsulated within the returned `Devres` instance' `data` will be @@ -237,7 +238,7 @@ pub fn new(dev: &Device, data: impl PinInit) -> Result }) } - fn data(&self) -> &Revocable { + pub(crate) fn data(&self) -> &Revocable { &self.inner.data } @@ -297,15 +298,19 @@ pub fn device(&self) -> &Device { /// #![cfg(CONFIG_PCI)] /// use kernel::{ /// device::Core, - /// devres::Devres, + /// devres::DevresLt, /// io::{ /// Io, /// IoKnownSize, // /// }, - /// pci, // + /// pci, + /// types::ForLt, // /// }; /// - /// fn from_core(dev: &pci::Device, devres: Devres>) -> Result { + /// fn from_core( + /// dev: &pci::Device, + /// devres: DevresLt)>, + /// ) -> Result { /// let bar = devres.access(dev.as_ref())?; /// /// let _ = bar.read32(0x0); @@ -353,7 +358,7 @@ unsafe impl Send for Devres {} // SAFETY: `Devres` can be shared with any task, if `T: Sync`. unsafe impl Sync for Devres {} -impl Drop for Devres { +impl Drop for Devres { fn drop(&mut self) { // SAFETY: When `drop` runs, it is guaranteed that nobody is accessing the revocable data // anymore, hence it is safe not to wait for the grace period to finish. @@ -369,6 +374,84 @@ fn drop(&mut self) { } } +/// Guard returned by [`DevresLt::try_access`]. +/// +/// Dereferences to `F::Of<'bound>`, applying [`ForLt::cast_ref`] to shorten the lifetime of the +/// stored data to the guard's borrow lifetime. +pub struct DevresGuard<'bound, F: ForLt>(RevocableGuard<'bound, F::Of<'static>>); + +impl<'bound, F: ForLt> core::ops::Deref for DevresGuard<'bound, F> { + type Target = F::Of<'bound>; + + fn deref(&self) -> &Self::Target { + F::cast_ref(&*self.0) + } +} + +/// Device-managed resource with [`ForLt`](trait@ForLt)-aware access. +/// +/// `DevresLt` wraps [`Devres`] and applies [`ForLt::cast_ref`] in its access methods to shorten +/// the stored `'static` lifetime to the caller's borrow lifetime. This prevents transmuted +/// `'static` lifetimes from leaking to users. +/// +/// Use this for resource types that implement [`ForLt`](trait@ForLt) and are stored with a +/// transmuted `'static` lifetime (e.g. [`pci::Bar`]). +/// +/// [`pci::Bar`]: crate::pci::Bar +pub struct DevresLt(Devres>) +where + F::Of<'static>: Send; + +impl DevresLt +where + F::Of<'static>: Send, +{ + /// Creates a new [`DevresLt`] instance of the given `data`. + pub fn new(dev: &Device, data: impl PinInit, E>) -> Result + where + Error: From, + { + Ok(Self(Devres::new(dev, data)?)) + } + + /// Return a reference of the [`Device`] this [`DevresLt`] instance has been created with. + pub fn device(&self) -> &Device { + self.0.device() + } + + /// Obtain `&'bound F::Of<'bound>`, bypassing the [`Revocable`]. + /// + /// This method works like [`Devres::access`], but shortens the returned reference's lifetime + /// from `'static` to `'bound` via [`ForLt::cast_ref`]. + pub fn access<'bound>( + &'bound self, + dev: &'bound Device, + ) -> Result<&'bound F::Of<'bound>> { + self.0.access(dev).map(F::cast_ref) + } + + /// [`DevresLt`] accessor for [`Revocable::try_access`]. + pub fn try_access(&self) -> Option> { + self.0.data().try_access().map(DevresGuard) + } + + /// [`DevresLt`] accessor for [`Revocable::try_access_with`]. + pub fn try_access_with(&self, f: G) -> Option + where + G: for<'bound> FnOnce(&'bound F::Of<'bound>) -> R, + { + self.0.data().try_access_with(|data| f(F::cast_ref(data))) + } + + /// [`DevresLt`] accessor for [`Revocable::try_access_with_guard`]. + pub fn try_access_with_guard<'bound>( + &'bound self, + guard: &'bound rcu::Guard, + ) -> Option<&'bound F::Of<'bound>> { + self.0.data().try_access_with_guard(guard).map(F::cast_ref) + } +} + /// Consume `data` and [`Drop::drop`] `data` once `dev` is unbound. fn register_foreign

(dev: &Device, data: P) -> Result where -- 2.54.0