rust: dma: add zeroed constructor to `Coherent`

These constructors create a coherent container of a single object
instead of slice. They are named `zeroed` and `zeroed_with_attrs` to
emphasis that they are created initialized zeroed. It is intended that
there'll be new constructors that take `PinInit` instead of zeroing.

Signed-off-by: Gary Guo <gary@garyguo.net>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Link: https://patch.msgid.link/20260320194626.36263-4-dakr@kernel.org
[ Use kernel import style. - Danilo ]
Signed-off-by: Danilo Krummrich <dakr@kernel.org>

1 files changed, 9 insertions, 4 deletions

diff --git a/samples/rust/rust_dma.rs b/samples/rust/rust_dma.rs
index ce39b5545097..129bb4b39c04 100644
--- a/samples/rust/rust_dma.rs
+++ b/samples/rust/rust_dma.rs
@@ -6,7 +6,12 @@
 
 use kernel::{
     device::Core,
-    dma::{CoherentAllocation, DataDirection, Device, DmaMask},
+    dma::{
+        Coherent,
+        DataDirection,
+        Device,
+        DmaMask, //
+    },
     page, pci,
     prelude::*,
     scatterlist::{Owned, SGTable},
@@ -16,7 +21,7 @@ use kernel::{
 #[pin_data(PinnedDrop)]
 struct DmaSampleDriver {
     pdev: ARef<pci::Device>,
-    ca: CoherentAllocation<MyStruct>,
+    ca: Coherent<[MyStruct]>,
     #[pin]
     sgt: SGTable<Owned<VVec<u8>>>,
 }
@@ -64,8 +69,8 @@ impl pci::Driver for DmaSampleDriver {
             // SAFETY: There are no concurrent calls to DMA allocation and mapping primitives.
             unsafe { pdev.dma_set_mask_and_coherent(mask)? };
 
-            let ca: CoherentAllocation<MyStruct> =
-                CoherentAllocation::alloc_coherent(pdev.as_ref(), TEST_VALUES.len(), GFP_KERNEL)?;
+            let ca: Coherent<[MyStruct]> =
+                Coherent::zeroed_slice(pdev.as_ref(), TEST_VALUES.len(), GFP_KERNEL)?;
 
             for (i, value) in TEST_VALUES.into_iter().enumerate() {
                 kernel::dma_write!(ca, [i]?, MyStruct::new(value.0, value.1));