+ /// Returns the CPU-addressable region as a slice.
+ pub fn cpu_buf(&self) -> &[T]
+ {
+ // SAFETY: The pointer is valid due to type invariant on `CoherentAllocation` and
+ // is valid for reads for `self.count * size_of::<T>` bytes.
+ unsafe { core::slice::from_raw_parts(self.cpu_addr, self.count) }
Immutable slices require that the data does not change while the
reference is live. Is that the case? If so, your safety comment should
explain that.
+ }
+
+ /// Performs the same functionality as `cpu_buf`, except that a mutable slice is returned.
+ pub fn cpu_buf_mut(&mut self) -> &mut [T]
+ {
+ // SAFETY: The pointer is valid due to type invariant on `CoherentAllocation` and
+ // is valid for reads for `self.count * size_of::<T>` bytes.
+ unsafe { core::slice::from_raw_parts_mut(self.cpu_addr, self.count) }
Mutable slices require that the data is not written to *or read* by
anybody else while the reference is live. Is that the case? If so,
your safety comment should explain that.
The buffer will probably be shared between the CPU and some hardware device, since this is the
point of the dma mapping API.
It’s up to the caller to ensure that no hardware operations that involve the buffer are currently taking
place while the slices above are alive.
I think that adding that as a safety requirement to `cpu_buf` and `cpu_buf_mut` will be sufficient.
+ }
+}
+
+impl<T: AsBytes + FromBytes> Drop for CoherentAllocation<T> {
+ fn drop(&mut self) {
+ let size = self.count * core::mem::size_of::<T>();
+ // SAFETY: the device, cpu address, and the dma handle is valid due to the
+ // type invariants on `CoherentAllocation`.
+ unsafe { bindings::dma_free_attrs(self.dev.as_raw(), size,
+ self.cpu_addr as _,
+ self.dma_handle,
+ self.dma_attrs.as_raw(),) }
+ }
+}
diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
index e1065a7551a3..6e90ebf5a130 100644
--- a/rust/kernel/lib.rs
+++ b/rust/kernel/lib.rs
@@ -35,6 +35,7 @@
mod build_assert;
pub mod cred;
pub mod device;
+pub mod dma;
pub mod error;
#[cfg(CONFIG_RUST_FW_LOADER_ABSTRACTIONS)]
pub mod firmware;
—
2.43.0
— Daniel