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Message-Id: <20250521-nova-frts-v4-1-05dfd4f39479@nvidia.com>
Date: Wed, 21 May 2025 15:44:56 +0900
From: Alexandre Courbot <acourbot@...dia.com>
To: 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>, Alice Ryhl <aliceryhl@...gle.com>,
Trevor Gross <tmgross@...ch.edu>, Danilo Krummrich <dakr@...nel.org>,
David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>
Cc: John Hubbard <jhubbard@...dia.com>, Ben Skeggs <bskeggs@...dia.com>,
Joel Fernandes <joelagnelf@...dia.com>, Timur Tabi <ttabi@...dia.com>,
Alistair Popple <apopple@...dia.com>, linux-kernel@...r.kernel.org,
rust-for-linux@...r.kernel.org, nouveau@...ts.freedesktop.org,
dri-devel@...ts.freedesktop.org, Alexandre Courbot <acourbot@...dia.com>
Subject: [PATCH v4 01/20] rust: dma: expose the count and size of
CoherentAllocation
These properties are very useful to have and should be accessible.
Signed-off-by: Alexandre Courbot <acourbot@...dia.com>
---
rust/kernel/dma.rs | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)
diff --git a/rust/kernel/dma.rs b/rust/kernel/dma.rs
index 605e01e35715667f93297fd9ec49d8e7032e0910..2a60eefa47dfc1f836c30ee342e26c6ff3e9b13a 100644
--- a/rust/kernel/dma.rs
+++ b/rust/kernel/dma.rs
@@ -129,6 +129,10 @@ pub mod attrs {
//
// Hence, find a way to revoke the device resources of a `CoherentAllocation`, but not the
// entire `CoherentAllocation` including the allocated memory itself.
+//
+// # Invariants
+//
+// The size in bytes of the allocation is equal to `size_of::<T> * count()`.
pub struct CoherentAllocation<T: AsBytes + FromBytes> {
dev: ARef<Device>,
dma_handle: bindings::dma_addr_t,
@@ -201,6 +205,20 @@ pub fn alloc_coherent(
CoherentAllocation::alloc_attrs(dev, count, gfp_flags, Attrs(0))
}
+ /// Returns the number of elements `T` in this allocation.
+ ///
+ /// Note that this is not the size of the allocation in bytes, which is provided by
+ /// [`Self::size`].
+ pub fn count(&self) -> usize {
+ self.count
+ }
+
+ /// Returns the size in bytes of this allocation.
+ pub fn size(&self) -> usize {
+ // As per the invariants of `CoherentAllocation`.
+ self.count * core::mem::size_of::<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
--
2.49.0
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