From 05aa6fb1c21d7fb9df735da24096d793223789d5 Mon Sep 17 00:00:00 2001 From: Danilo Krummrich Date: Thu, 28 Aug 2025 15:32:16 +0200 Subject: rust: scatterlist: Add abstraction for sg_table Add a safe Rust abstraction for the kernel's scatter-gather list facilities (`struct scatterlist` and `struct sg_table`). This commit introduces `SGTable`, a wrapper that uses a generic parameter to provide compile-time guarantees about ownership and lifetime. The abstraction provides two primary states: - `SGTable>`: Represents a table whose resources are fully managed by Rust. It takes ownership of a page provider `P`, allocates the underlying `struct sg_table`, maps it for DMA, and handles all cleanup automatically upon drop. The DMA mapping's lifetime is tied to the associated device using `Devres`, ensuring it is correctly unmapped before the device is unbound. - `SGTable` (or just `SGTable`): A zero-cost representation of an externally managed `struct sg_table`. It is created from a raw pointer using `SGTable::from_raw()` and provides a lifetime-bound reference (`&'a SGTable`) for operations like iteration. The API exposes a safe iterator that yields `&SGEntry` references, allowing drivers to easily access the DMA address and length of each segment in the list. Reviewed-by: Alice Ryhl Reviewed-by: Alexandre Courbot Tested-by: Alexandre Courbot Reviewed-by: Daniel Almeida Reviewed-by: Lyude Paul Co-developed-by: Abdiel Janulgue Signed-off-by: Abdiel Janulgue Link: https://lore.kernel.org/r/20250828133323.53311-4-dakr@kernel.org Signed-off-by: Danilo Krummrich --- rust/helpers/helpers.c | 1 + rust/helpers/scatterlist.c | 24 ++++++++++++++++++++++++ 2 files changed, 25 insertions(+) create mode 100644 rust/helpers/scatterlist.c (limited to 'rust/helpers') diff --git a/rust/helpers/helpers.c b/rust/helpers/helpers.c index 7cf7fe95e41d..e94542bf6ea7 100644 --- a/rust/helpers/helpers.c +++ b/rust/helpers/helpers.c @@ -39,6 +39,7 @@ #include "rcu.c" #include "refcount.c" #include "regulator.c" +#include "scatterlist.c" #include "security.c" #include "signal.c" #include "slab.c" diff --git a/rust/helpers/scatterlist.c b/rust/helpers/scatterlist.c new file mode 100644 index 000000000000..80c956ee09ab --- /dev/null +++ b/rust/helpers/scatterlist.c @@ -0,0 +1,24 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include + +dma_addr_t rust_helper_sg_dma_address(struct scatterlist *sg) +{ + return sg_dma_address(sg); +} + +unsigned int rust_helper_sg_dma_len(struct scatterlist *sg) +{ + return sg_dma_len(sg); +} + +struct scatterlist *rust_helper_sg_next(struct scatterlist *sg) +{ + return sg_next(sg); +} + +void rust_helper_dma_unmap_sgtable(struct device *dev, struct sg_table *sgt, + enum dma_data_direction dir, unsigned long attrs) +{ + return dma_unmap_sgtable(dev, sgt, dir, attrs); +} -- cgit