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Message-ID: <20250716150354.51081-3-dakr@kernel.org>
Date: Wed, 16 Jul 2025 17:02:47 +0200
From: Danilo Krummrich <dakr@...nel.org>
To: abdiel.janulgue@...il.com,
daniel.almeida@...labora.com,
robin.murphy@....com,
a.hindborg@...nel.org,
ojeda@...nel.org,
alex.gaynor@...il.com,
boqun.feng@...il.com,
gary@...yguo.net,
bjorn3_gh@...tonmail.com,
lossin@...nel.org,
aliceryhl@...gle.com,
tmgross@...ch.edu,
bhelgaas@...gle.com,
kwilczynski@...nel.org,
gregkh@...uxfoundation.org,
rafael@...nel.org
Cc: rust-for-linux@...r.kernel.org,
linux-pci@...r.kernel.org,
linux-kernel@...r.kernel.org,
Danilo Krummrich <dakr@...nel.org>
Subject: [PATCH v2 2/5] 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 <abdiel.janulgue@...il.com>
Signed-off-by: Danilo Krummrich <dakr@...nel.org>
---
rust/helpers/dma.c | 5 ++
rust/kernel/dma.rs | 112 +++++++++++++++++++++++++++++++++++++++++++--
2 files changed, 113 insertions(+), 4 deletions(-)
diff --git a/rust/helpers/dma.c b/rust/helpers/dma.c
index df8b8a77355a..6e741c197242 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 f0af23d08e8d..afd3ba538e3c 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 +18,111 @@
/// 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<device::Device<Core>> {}
+pub trait Device: AsRef<device::Device<Core>> {
+ /// 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`] 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()`.
+///
+/// # 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);
+///
+/// let mask_overflow = DmaMask::new(100);
+/// assert!(mask_overflow.is_err());
+/// # Ok::<(), Error>(())
+/// ```
+#[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`, returns [`EINVAL`].
+ #[inline]
+ pub const fn new(n: usize) -> Result<Self> {
+ 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.
///
--
2.50.0
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