From 101d66828a4eefb89b72256155feb6ec9abc144a Mon Sep 17 00:00:00 2001 From: Danilo Krummrich Date: Wed, 16 Jul 2025 17:02:47 +0200 Subject: [PATCH] rust: dma: add DMA addressing capabilities Implement `dma_set_mask()`, `dma_set_coherent_mask()` and `dma_set_mask_and_coherent()` in the `dma::Device` trait. Those methods are used to set up the device's DMA addressing capabilities. Reviewed-by: Abdiel Janulgue Reviewed-by: Daniel Almeida Reviewed-by: Greg Kroah-Hartman Link: https://lore.kernel.org/r/20250716150354.51081-3-dakr@kernel.org [ Add DmaMask::try_new(). - Danilo ] Signed-off-by: Danilo Krummrich --- rust/helpers/dma.c | 5 ++ rust/kernel/dma.rs | 143 +++++++++++++++++++++++++++++++++++++++++++-- 2 files changed, 144 insertions(+), 4 deletions(-) diff --git a/rust/helpers/dma.c b/rust/helpers/dma.c index df8b8a77355a3..6e741c1972425 100644 --- a/rust/helpers/dma.c +++ b/rust/helpers/dma.c @@ -14,3 +14,8 @@ void rust_helper_dma_free_attrs(struct device *dev, size_t size, void *cpu_addr, { dma_free_attrs(dev, size, cpu_addr, dma_handle, attrs); } + +int rust_helper_dma_set_mask_and_coherent(struct device *dev, u64 mask) +{ + return dma_set_mask_and_coherent(dev, mask); +} diff --git a/rust/kernel/dma.rs b/rust/kernel/dma.rs index 586524488e5d4..99dcf79f0897c 100644 --- a/rust/kernel/dma.rs +++ b/rust/kernel/dma.rs @@ -6,9 +6,9 @@ use crate::{ bindings, build_assert, device, - device::Bound, - error::code::*, - error::Result, + device::{Bound, Core}, + error::{to_result, Result}, + prelude::*, transmute::{AsBytes, FromBytes}, types::ARef, }; @@ -18,7 +18,142 @@ use crate::{ /// The [`dma::Device`](Device) trait should be implemented by bus specific device representations, /// where the underlying bus is DMA capable, such as [`pci::Device`](::kernel::pci::Device) or /// [`platform::Device`](::kernel::platform::Device). -pub trait Device: AsRef> {} +pub trait Device: AsRef> { + /// Set up the device's DMA streaming addressing capabilities. + /// + /// This method is usually called once from `probe()` as soon as the device capabilities are + /// known. + /// + /// # Safety + /// + /// This method must not be called concurrently with any DMA allocation or mapping primitives, + /// such as [`CoherentAllocation::alloc_attrs`]. + unsafe fn dma_set_mask(&self, mask: DmaMask) -> Result { + // SAFETY: + // - By the type invariant of `device::Device`, `self.as_ref().as_raw()` is valid. + // - The safety requirement of this function guarantees that there are no concurrent calls + // to DMA allocation and mapping primitives using this mask. + to_result(unsafe { bindings::dma_set_mask(self.as_ref().as_raw(), mask.value()) }) + } + + /// Set up the device's DMA coherent addressing capabilities. + /// + /// This method is usually called once from `probe()` as soon as the device capabilities are + /// known. + /// + /// # Safety + /// + /// This method must not be called concurrently with any DMA allocation or mapping primitives, + /// such as [`CoherentAllocation::alloc_attrs`]. + unsafe fn dma_set_coherent_mask(&self, mask: DmaMask) -> Result { + // SAFETY: + // - By the type invariant of `device::Device`, `self.as_ref().as_raw()` is valid. + // - The safety requirement of this function guarantees that there are no concurrent calls + // to DMA allocation and mapping primitives using this mask. + to_result(unsafe { bindings::dma_set_coherent_mask(self.as_ref().as_raw(), mask.value()) }) + } + + /// Set up the device's DMA addressing capabilities. + /// + /// This is a combination of [`Device::dma_set_mask`] and [`Device::dma_set_coherent_mask`]. + /// + /// This method is usually called once from `probe()` as soon as the device capabilities are + /// known. + /// + /// # Safety + /// + /// This method must not be called concurrently with any DMA allocation or mapping primitives, + /// such as [`CoherentAllocation::alloc_attrs`]. + unsafe fn dma_set_mask_and_coherent(&self, mask: DmaMask) -> Result { + // SAFETY: + // - By the type invariant of `device::Device`, `self.as_ref().as_raw()` is valid. + // - The safety requirement of this function guarantees that there are no concurrent calls + // to DMA allocation and mapping primitives using this mask. + to_result(unsafe { + bindings::dma_set_mask_and_coherent(self.as_ref().as_raw(), mask.value()) + }) + } +} + +/// A DMA mask that holds a bitmask with the lowest `n` bits set. +/// +/// Use [`DmaMask::new`] or [`DmaMask::try_new`] to construct a value. Values +/// are guaranteed to never exceed the bit width of `u64`. +/// +/// This is the Rust equivalent of the C macro `DMA_BIT_MASK()`. +#[derive(Debug, Clone, Copy, PartialEq, Eq)] +pub struct DmaMask(u64); + +impl DmaMask { + /// Constructs a `DmaMask` with the lowest `n` bits set to `1`. + /// + /// For `n <= 64`, sets exactly the lowest `n` bits. + /// For `n > 64`, results in a build error. + /// + /// # Examples + /// + /// ``` + /// use kernel::dma::DmaMask; + /// + /// let mask0 = DmaMask::new::<0>(); + /// assert_eq!(mask0.value(), 0); + /// + /// let mask1 = DmaMask::new::<1>(); + /// assert_eq!(mask1.value(), 0b1); + /// + /// let mask64 = DmaMask::new::<64>(); + /// assert_eq!(mask64.value(), u64::MAX); + /// + /// // Build failure. + /// // let mask_overflow = DmaMask::new::<100>(); + /// ``` + #[inline] + pub const fn new() -> Self { + let Ok(mask) = Self::try_new(N) else { + build_error!("Invalid DMA Mask."); + }; + + mask + } + + /// Constructs a `DmaMask` with the lowest `n` bits set to `1`. + /// + /// For `n <= 64`, sets exactly the lowest `n` bits. + /// For `n > 64`, returns [`EINVAL`]. + /// + /// # Examples + /// + /// ``` + /// use kernel::dma::DmaMask; + /// + /// let mask0 = DmaMask::try_new(0)?; + /// assert_eq!(mask0.value(), 0); + /// + /// let mask1 = DmaMask::try_new(1)?; + /// assert_eq!(mask1.value(), 0b1); + /// + /// let mask64 = DmaMask::try_new(64)?; + /// assert_eq!(mask64.value(), u64::MAX); + /// + /// let mask_overflow = DmaMask::try_new(100); + /// assert!(mask_overflow.is_err()); + /// # Ok::<(), Error>(()) + /// ``` + #[inline] + pub const fn try_new(n: u32) -> Result { + Ok(Self(match n { + 0 => 0, + 1..=64 => u64::MAX >> (64 - n), + _ => return Err(EINVAL), + })) + } + + /// Returns the underlying `u64` bitmask value. + #[inline] + pub const fn value(&self) -> u64 { + self.0 + } +} /// Possible attributes associated with a DMA mapping. /// -- 2.47.2