From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 2CC353446AD; Thu, 18 Jun 2026 23:09:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781824170; cv=none; b=D3CrXtrT7w1j6O1bvRwHr70XZiwloqG40+fyB4quRUkkyboIDoGZcJ23WybM36+Qz90v+7PXPJp6JmVGUpFAnXK66rTkWY1J+5cnFr4flBOgh+d8/Wf5y3uDRQxcHE6NztYFuwxRYqHHCbKgmVGzQ2VJTl16nH61QGo5sWZ8MjA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781824170; c=relaxed/simple; bh=aPw+3y8zYEqDYzHyae8a9mYXem4pCs/tyI3KcwXC5OA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=CccXQqy0RLfAbBdBATvjmLAUXKe2OWAldFXCaDnHGVezmJi9pFpZYdfWT8+93XYpO7C5+ovkNOAVBtJRlm29i/ysd5UPsIWf8yzLSENjkQPPVf/AIpVajpQ6FpLH0hAfUf9LUS86TLMJPd7jkUKPESIHYrT+H8Sx1xzao1woX/o= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Juo9SkvR; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Juo9SkvR" Received: by smtp.kernel.org (Postfix) with ESMTPSA id BF3E31F00A3E; Thu, 18 Jun 2026 23:09:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1781824168; bh=B2MFtQTw47PQHqeH1+d+WYsv/KWPhJupCuzKaQmKk1Y=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=Juo9SkvRQPdizSVgBGH7gB7VyCUjfM6odbedYPfjSehH7ngbt/dx6mUP2s6hclfma oPBJLmogvUViAtL5ld4DxoStERH4TYtZJdZ7aR8SwmE6mi1UN2sSQtb5qLWlDqZ5tn e4q39Jcb50zedTnVJ76mlYxaarFy13pW9ck6BAr2kcfNhfrC54sHHJYABGO+c89N3i Wy3SWPZjRCGxVnNc+PElQxbEmMg7LLbHMQTAtzjqokWgszkvnaAHNfgaRqe0DfYMO/ dLYpy/WY27zzL9fDn6JqI/ftbdMhP8GHZmEJ35M/gCwLwNwfirMySSDW6mNbk6LRPa lq7XCf95gkhQw== From: Danilo Krummrich To: gregkh@linuxfoundation.org, rafael@kernel.org, dakr@kernel.org, ojeda@kernel.org, boqun@kernel.org, gary@garyguo.net, bjorn3_gh@protonmail.com, lossin@kernel.org, a.hindborg@kernel.org, aliceryhl@google.com, tmgross@umich.edu, acourbot@nvidia.com, ecourtney@nvidia.com, m.wilczynski@samsung.com, david.m.ertman@intel.com, ira.weiny@intel.com, leon@kernel.org, daniel.almeida@collabora.com, bhelgaas@google.com, kwilczynski@kernel.org Cc: driver-core@lists.linux.dev, linux-kernel@vger.kernel.org, nova-gpu@lists.linux.dev, dri-devel@lists.freedesktop.org, linux-pwm@vger.kernel.org, rust-for-linux@vger.kernel.org Subject: [PATCH v3 7/7] rust: io: mem: return DevresLt from IoMem/ExclusiveIoMem::into_devres() Date: Fri, 19 Jun 2026 01:08:33 +0200 Message-ID: <20260618230834.812007-8-dakr@kernel.org> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260618230834.812007-1-dakr@kernel.org> References: <20260618230834.812007-1-dakr@kernel.org> Precedence: bulk X-Mailing-List: nova-gpu@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Implement ForLt and CovariantForLt for IoMem<'static, SIZE> and ExclusiveIoMem<'static, SIZE> so that DevresLt can shorten the stored 'static lifetime back to the caller's borrow lifetime. CovariantForLt is sound because both types only hold &'a Device, which is covariant over 'a. Since DevresLt::new() handles the lifetime transmutation internally, into_devres() no longer needs an explicit transmute to 'static. Add DevresIoMem and DevresExclusiveIoMem type aliases. Signed-off-by: Danilo Krummrich --- drivers/pwm/pwm_th1520.rs | 5 ++- rust/kernel/io/mem.rs | 65 +++++++++++++++++++++++++++------------ 2 files changed, 47 insertions(+), 23 deletions(-) diff --git a/drivers/pwm/pwm_th1520.rs b/drivers/pwm/pwm_th1520.rs index 3e3fa51ccef9..7102c60fd14b 100644 --- a/drivers/pwm/pwm_th1520.rs +++ b/drivers/pwm/pwm_th1520.rs @@ -24,9 +24,8 @@ use kernel::{ clk::Clk, device::{Bound, Core, Device}, - devres, io::{ - mem::IoMem, + mem::DevresIoMem, Io, // }, of, platform, @@ -86,7 +85,7 @@ struct Th1520WfHw { #[pin_data(PinnedDrop)] struct Th1520PwmDriverData { #[pin] - iomem: devres::Devres>, + iomem: DevresIoMem, clk: Clk, } diff --git a/rust/kernel/io/mem.rs b/rust/kernel/io/mem.rs index fc2a3e24f8d5..4691a01a3cf7 100644 --- a/rust/kernel/io/mem.rs +++ b/rust/kernel/io/mem.rs @@ -9,7 +9,7 @@ Bound, Device, // }, - devres::Devres, + devres::DevresLt, io::{ self, resource::{ @@ -20,6 +20,10 @@ MmioRaw, // }, prelude::*, + types::{ + CovariantForLt, + ForLt, // + }, }; /// An IO request for a specific device and resource. @@ -172,6 +176,19 @@ pub struct ExclusiveIoMem<'a, const SIZE: usize> { _region: Region, } +impl ForLt for ExclusiveIoMem<'static, SIZE> { + type Of<'a> = ExclusiveIoMem<'a, SIZE>; +} + +// SAFETY: `ExclusiveIoMem<'a, SIZE>` is covariant over `'a`; it holds an `IoMem<'a, SIZE>`, +// which holds `&'a Device`, which is covariant. +unsafe impl CovariantForLt for ExclusiveIoMem<'static, SIZE> {} + +/// A device-managed exclusive I/O memory region. +/// +/// See [`ExclusiveIoMem::into_devres`]. +pub type DevresExclusiveIoMem = DevresLt>; + impl<'a, const SIZE: usize> ExclusiveIoMem<'a, SIZE> { /// Creates a new `ExclusiveIoMem` instance. fn ioremap(dev: &'a Device, resource: &Resource) -> Result { @@ -198,15 +215,13 @@ fn ioremap(dev: &'a Device, resource: &Resource) -> Result { /// Consume the `ExclusiveIoMem` and register it as a device-managed resource. /// - /// The returned `Devres>` can outlive the original lifetime - /// `'a`. Access to the I/O memory is revoked when the device is unbound. - pub fn into_devres(self) -> Result>> { - // SAFETY: Casting to `'static` is sound because `Devres` guarantees the - // `ExclusiveIoMem` does not actually outlive the device -- access is revoked and the - // resource is released when the device is unbound. - let iomem: ExclusiveIoMem<'static, SIZE> = unsafe { core::mem::transmute(self) }; - let dev = iomem.iomem.dev; - Devres::new(dev, iomem) + /// The returned [`DevresExclusiveIoMem`] can outlive the original borrow and be stored in + /// driver data. Access to the I/O memory is revoked automatically when the device is unbound. + pub fn into_devres(self) -> Result> { + let dev = self.iomem.dev; + // SAFETY: `ExclusiveIoMem` only holds a device reference and an I/O mapping, both of + // which remain valid for the device's full bound scope, not just for `'a`. + unsafe { DevresLt::new(dev, self) } } } @@ -232,6 +247,19 @@ pub struct IoMem<'a, const SIZE: usize = 0> { io: MmioRaw, } +impl ForLt for IoMem<'static, SIZE> { + type Of<'a> = IoMem<'a, SIZE>; +} + +// SAFETY: `IoMem<'a, SIZE>` is covariant over `'a`; it holds `&'a Device`, +// which is covariant. +unsafe impl CovariantForLt for IoMem<'static, SIZE> {} + +/// A device-managed I/O memory region. +/// +/// See [`IoMem::into_devres`]. +pub type DevresIoMem = DevresLt>; + impl<'a, const SIZE: usize> IoMem<'a, SIZE> { fn ioremap(dev: &'a Device, resource: &Resource) -> Result { // Note: Some ioremap() implementations use types that depend on the CPU @@ -271,16 +299,13 @@ fn ioremap(dev: &'a Device, resource: &Resource) -> Result { /// Consume the `IoMem` and register it as a device-managed resource. /// - /// The returned `Devres>` can outlive the original - /// lifetime `'a`. Access to the I/O memory is revoked when the device - /// is unbound. - pub fn into_devres(self) -> Result>> { - // SAFETY: Casting to `'static` is sound because `Devres` guarantees the `IoMem` does not - // actually outlive the device -- access is revoked and the resource is released when the - // device is unbound. - let iomem: IoMem<'static, SIZE> = unsafe { core::mem::transmute(self) }; - let dev = iomem.dev; - Devres::new(dev, iomem) + /// The returned [`DevresIoMem`] can outlive the original borrow and be stored in driver data. + /// Access to the I/O memory is revoked automatically when the device is unbound. + pub fn into_devres(self) -> Result> { + let dev = self.dev; + // SAFETY: `IoMem` only holds a device reference and an I/O mapping, both of which + // remain valid for the device's full bound scope, not just for `'a`. + unsafe { DevresLt::new(dev, self) } } } -- 2.54.0