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a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1774036022; bh=ju9WyBxPqyhdguAHgPK1Hx/Tksq0dRThuffsKQ3jlpE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=YDSa3Qr6JFZRqqZLQfMA9a0TfK0uoNtJcg4U8dI8QYEkz2CP7v7g1K0IFpZj9yLlI dXPS94g4ZCX7jFUhgMeh7cVBfYF8zmqMWmcod2/fWEsugYVFtM6ENu5znrCin3nqbC L5sm9dQ3VQOPiO2UnvKphnuwXH03tB6GpKICe3tPbEBy020QkUKW0fmGc3LqhkNh+z /HPdt35vQTisvSGbtXMO5tWL5zu8frMsB2kmcbqBlM7wH2oACBL/R5DFIu/m0gHtap PU3UhYo/FntqaZcuQZx56wdknXiKMglFIvM4CCYzHvrfKOf+cnp3atWhAwtYkCv+CU MEw+MB2D3beTg== From: Danilo Krummrich To: aliceryhl@google.com, acourbot@nvidia.com, ojeda@kernel.org, boqun@kernel.org, gary@garyguo.net, bjorn3_gh@protonmail.com, lossin@kernel.org, a.hindborg@kernel.org, tmgross@umich.edu, abdiel.janulgue@gmail.com, daniel.almeida@collabora.com, robin.murphy@arm.com Subject: [PATCH v2 5/8] rust: dma: add Coherent:init() and Coherent::init_with_attrs() Date: Fri, 20 Mar 2026 20:45:40 +0100 Message-ID: <20260320194626.36263-6-dakr@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260320194626.36263-1-dakr@kernel.org> References: <20260320194626.36263-1-dakr@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Message-ID-Hash: 6WPCRPMZ63A4SDO53XLFVMVCAV4JBW7O X-Message-ID-Hash: 6WPCRPMZ63A4SDO53XLFVMVCAV4JBW7O X-MailFrom: dakr@kernel.org X-Mailman-Rule-Hits: nonmember-moderation X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency; loop; banned-address; member-moderation CC: driver-core@lists.linux.dev, nouveau@lists.freedesktop.org, dri-devel@lists.freedesktop.org, rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org, Danilo Krummrich X-Mailman-Version: 3.3.8 Precedence: list List-Id: Nouveau development list Archived-At: Archived-At: List-Archive: List-Archive: List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: Analogous to Coherent::zeroed() and Coherent::zeroed_with_attrs(), add Coherent:init() and Coherent::init_with_attrs() which both take an impl Init argument initializing the DMA coherent memory. Compared to CoherentInit, Coherent::init() is a one-shot constructor that runs an Init closure and immediately exposes the DMA handle, whereas CoherentInit is a multi-stage initializer that provides safe &mut T access by withholding the DMA address until converted to Coherent. Signed-off-by: Danilo Krummrich --- rust/kernel/dma.rs | 38 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 38 insertions(+) diff --git a/rust/kernel/dma.rs b/rust/kernel/dma.rs index cefb54f0424a..6d2bec52806b 100644 --- a/rust/kernel/dma.rs +++ b/rust/kernel/dma.rs @@ -709,6 +709,44 @@ pub fn zeroed(dev: &device::Device, gfp_flags: kernel::alloc::Flags) -> R Self::zeroed_with_attrs(dev, gfp_flags, Attrs(0)) } + /// Same as [`Coherent::zeroed_with_attrs`], but instead of a zero-initialization the memory is + /// initialized with `init`. + pub fn init_with_attrs( + dev: &device::Device, + gfp_flags: kernel::alloc::Flags, + dma_attrs: Attrs, + init: impl Init, + ) -> Result + where + Error: From, + { + let dmem = Self::alloc_with_attrs(dev, gfp_flags, dma_attrs)?; + let ptr = dmem.as_mut_ptr(); + + // SAFETY: + // - `ptr` is valid, properly aligned, and points to exclusively owned memory. + // - If `__init` fails, `self` is dropped, which safely frees the underlying `Coherent`'s + // DMA memory. `T: AsBytes + FromBytes` ensures there are no complex `Drop` requirements + // we are bypassing. + unsafe { init.__init(ptr)? }; + + Ok(dmem) + } + + /// Same as [`Coherent::zeroed`], but instead of a zero-initialization the memory is initialized + /// with `init`. + #[inline] + pub fn init( + dev: &device::Device, + gfp_flags: kernel::alloc::Flags, + init: impl Init, + ) -> Result + where + Error: From, + { + Self::init_with_attrs(dev, gfp_flags, Attrs(0), init) + } + /// Allocates a region of `[T; len]` of coherent memory. fn alloc_slice_with_attrs( dev: &device::Device, -- 2.53.0