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

Abdiel Janulgue
2025-03-07T11:08:45Z

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@gmail.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