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rust: dma: use NonNull<T> instead of *mut T

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In struct CoherentAllocation, use NonNull<T> instead of a raw *mut T for
the CPU address; the CPU address of a valid CoherentAllocation won't
ever be NULL.

Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Link: https://patch.msgid.link/20251103190655.2326191-2-dakr@kernel.org
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
This commit is contained in:
Danilo Krummrich
2025-11-03 20:06:50 +01:00
parent f7afdc4737
commit ededb7bcdf
1 changed files with 8 additions and 9 deletions
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17
rust/kernel/dma.rs
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@@ -12,6 +12,7 @@ use crate::{
sync::aref::ARef,
transmute::{AsBytes, FromBytes},
};
use core::ptr::NonNull;
/// DMA address type.
///
@@ -358,7 +359,7 @@ pub struct CoherentAllocation<T: AsBytes + FromBytes> {
dev: ARef<device::Device>,
dma_handle: DmaAddress,
count: usize,
cpu_addr: *mut T,
cpu_addr: NonNull<T>,
dma_attrs: Attrs,
}
@@ -392,7 +393,7 @@ impl<T: AsBytes + FromBytes> CoherentAllocation<T> {
.ok_or(EOVERFLOW)?;
let mut dma_handle = 0;
// SAFETY: Device pointer is guaranteed as valid by the type invariant on `Device`.
let ret = unsafe {
let addr = unsafe {
bindings::dma_alloc_attrs(
dev.as_raw(),
size,
@@ -401,9 +402,7 @@ impl<T: AsBytes + FromBytes> CoherentAllocation<T> {
dma_attrs.as_raw(),
)
};
if ret.is_null() {
return Err(ENOMEM);
}
let addr = NonNull::new(addr).ok_or(ENOMEM)?;
// INVARIANT:
// - We just successfully allocated a coherent region which is accessible for
// `count` elements, hence the cpu address is valid. We also hold a refcounted reference
@@ -414,7 +413,7 @@ impl<T: AsBytes + FromBytes> CoherentAllocation<T> {
dev: dev.into(),
dma_handle,
count,
cpu_addr: ret.cast::<T>(),
cpu_addr: addr.cast(),
dma_attrs,
})
}
@@ -446,13 +445,13 @@ impl<T: AsBytes + FromBytes> CoherentAllocation<T> {
/// Returns the base address to the allocated region in the CPU's virtual address space.
pub fn start_ptr(&self) -> *const T {
self.cpu_addr
self.cpu_addr.as_ptr()
}
/// Returns the base address to the allocated region in the CPU's virtual address space as
/// a mutable pointer.
pub fn start_ptr_mut(&mut self) -> *mut T {
self.cpu_addr
self.cpu_addr.as_ptr()
}
/// Returns a DMA handle which may be given to the device as the DMA address base of
@@ -580,7 +579,7 @@ impl<T: AsBytes + FromBytes> CoherentAllocation<T> {
// and we've just checked that the range and index is within bounds.
// - `offset` can't overflow since it is smaller than `self.count` and we've checked
// that `self.count` won't overflow early in the constructor.
Ok(unsafe { self.cpu_addr.add(offset) })
Ok(unsafe { self.cpu_addr.as_ptr().add(offset) })
}
/// Reads the value of `field` and ensures that its type is [`FromBytes`].