linux-kernel - [PATCH v13 4/7] rust: device: add dma addressing capabilities

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Message-ID: <20250307110821.1703422-5-abdiel.janulgue@gmail.com>
Date: Fri,  7 Mar 2025 13:06:21 +0200
From: Abdiel Janulgue <abdiel.janulgue@...il.com>
To: rust-for-linux@...r.kernel.org,
	daniel.almeida@...labora.com,
	dakr@...nel.org,
	robin.murphy@....com,
	aliceryhl@...gle.com
Cc: Miguel Ojeda <ojeda@...nel.org>,
	Alex Gaynor <alex.gaynor@...il.com>,
	Boqun Feng <boqun.feng@...il.com>,
	Gary Guo <gary@...yguo.net>,
	Björn Roy Baron <bjorn3_gh@...tonmail.com>,
	Benno Lossin <benno.lossin@...ton.me>,
	Andreas Hindborg <a.hindborg@...nel.org>,
	Trevor Gross <tmgross@...ch.edu>,
	Valentin Obst <kernel@...entinobst.de>,
	linux-kernel@...r.kernel.org (open list),
	Christoph Hellwig <hch@....de>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	airlied@...hat.com,
	iommu@...ts.linux.dev (open list:DMA MAPPING HELPERS),
	Abdiel Janulgue <abdiel.janulgue@...il.com>
Subject: [PATCH v13 4/7] rust: device: add dma addressing capabilities

Add functions to set the DMA mask to inform the kernel about the
device's DMA addressing capabilities.

Signed-off-by: Abdiel Janulgue <abdiel.janulgue@...il.com>
---
 rust/helpers/dma.c     |  8 ++++++++
 rust/helpers/helpers.c |  1 +
 rust/kernel/device.rs  | 29 +++++++++++++++++++++++++++++
 3 files changed, 38 insertions(+)
 create mode 100644 rust/helpers/dma.c

diff --git a/rust/helpers/dma.c b/rust/helpers/dma.c
new file mode 100644
index 000000000000..8eb482386f93
--- /dev/null
+++ b/rust/helpers/dma.c
@@ -0,0 +1,8 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/dma-mapping.h>
+
+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/helpers/helpers.c b/rust/helpers/helpers.c
index 0640b7e115be..8f3808c8b7fe 100644
--- a/rust/helpers/helpers.c
+++ b/rust/helpers/helpers.c
@@ -13,6 +13,7 @@
 #include "build_bug.c"
 #include "cred.c"
 #include "device.c"
+#include "dma.c"
 #include "err.c"
 #include "fs.c"
 #include "io.c"
diff --git a/rust/kernel/device.rs b/rust/kernel/device.rs
index db2d9658ba47..f9d3d4f60ddb 100644
--- a/rust/kernel/device.rs
+++ b/rust/kernel/device.rs
@@ -6,10 +6,12 @@
 
 use crate::{
     bindings,
+    error::Result,
     str::CStr,
     types::{ARef, Opaque},
 };
 use core::{fmt, ptr};
+use kernel::prelude::*;
 
 #[cfg(CONFIG_PRINTK)]
 use crate::c_str;
@@ -187,6 +189,33 @@ pub fn property_present(&self, name: &CStr) -> bool {
         // SAFETY: By the invariant of `CStr`, `name` is null-terminated.
         unsafe { bindings::device_property_present(self.as_raw().cast_const(), name.as_char_ptr()) }
     }
+
+    /// Inform the kernel about the device's DMA addressing capabilities.
+    ///
+    /// Set both the DMA mask and the coherent DMA mask to the same thing.
+    /// Note that we don't check the return value from the C `dma_set_coherent_mask`
+    /// as the DMA API guarantees that the coherent DMA mask can be set to
+    /// the same or smaller than the streaming DMA mask.
+    pub fn dma_set_mask_and_coherent(&mut self, mask: u64) -> Result {
+        // SAFETY: device pointer is guaranteed as valid by invariant on `Device`.
+        let ret = unsafe { bindings::dma_set_mask_and_coherent(self.as_raw(), mask) };
+        if ret != 0 {
+            Err(Error::from_errno(ret))
+        } else {
+            Ok(())
+        }
+    }
+
+    /// Same as [`dma_set_mask_and_coherent`], but set the mask only for streaming mappings.
+    pub fn dma_set_mask(&mut self, mask: u64) -> Result {
+        // SAFETY: device pointer is guaranteed as valid by invariant on `Device`.
+        let ret = unsafe { bindings::dma_set_mask(self.as_raw(), mask) };
+        if ret != 0 {
+            Err(Error::from_errno(ret))
+        } else {
+            Ok(())
+        }
+    }
 }
 
 // SAFETY: Instances of `Device` are always reference-counted.
-- 
2.43.0