From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 90B36CD6E5D for ; Wed, 3 Jun 2026 01:11:06 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 0498010F734; Wed, 3 Jun 2026 01:11:06 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.b="LgEpdA1y"; dkim-atps=neutral Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by gabe.freedesktop.org (Postfix) with ESMTPS id 1D6A210F733 for ; Wed, 3 Jun 2026 01:11:04 +0000 (UTC) Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 056DA43B57; Wed, 3 Jun 2026 01:11:04 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1964E1F00898; Wed, 3 Jun 2026 01:10:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1780449063; bh=6kwWxpERwhRfbh+IYbhqXFQAvVIriNywyEds62Ao6CA=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=LgEpdA1ysW/6aW4sNfMAY+vmwXWjmraQAX/521n//865SRjUM0K5USCa9W0rmp8mV kJtjn0vbIlFRpLBSMH43IbdFtr5qpA/M8wS61jkuHqzV7pdAmYFVADgmJfM6g4LFbX s5zVBwIWG5EciXEKIUiIL2smDUQttiYVMhQk1/KnPtxfDjZlQ875R9Mz6N7/29y4Gn R+vrN2bF5qjOx7t8sh+3y0GFri5uDP2GcL/qsEaoDAO1YWilBBoD+u+mqmgVufANnA ykfuJna16K/nJ4u36Odn3M0lIuL2fh2YVfrSjmvTdn/r67lelpXpXm1CuGc9lLcdsd mOzs+75PWde7g== 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 v2 7/7] rust: io: mem: return DevresLt from IoMem/ExclusiveIoMem::into_devres() Date: Wed, 3 Jun 2026 03:10:18 +0200 Message-ID: <20260603011020.2073650-8-dakr@kernel.org> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260603011020.2073650-1-dakr@kernel.org> References: <20260603011020.2073650-1-dakr@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" 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 48808cd80737..7e3a06ed369f 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, @@ -92,7 +91,7 @@ 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