linux-kernel - [PATCH v13 3/7] rust: pci: impl AsMut<Device> for pci::Device

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Message-ID: <20250307110821.1703422-4-abdiel.janulgue@gmail.com>
Date: Fri,  7 Mar 2025 13:06:20 +0200
From: Abdiel Janulgue <abdiel.janulgue@...il.com>
To: rust-for-linux@...r.kernel.org,
	daniel.almeida@...labora.com,
	dakr@...nel.org,
	robin.murphy@....com,
	aliceryhl@...gle.com
Cc: 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>,
	Trevor Gross <tmgross@...ch.edu>,
	Valentin Obst <kernel@...entinobst.de>,
	linux-kernel@...r.kernel.org (open list),
	Christoph Hellwig <hch@....de>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	airlied@...hat.com,
	iommu@...ts.linux.dev (open list:DMA MAPPING HELPERS)
Subject: [PATCH v13 3/7] rust: pci: impl AsMut<Device> for pci::Device

From: Danilo Krummrich <dakr@...nel.org>

Some device methods require mutable references, since they change the
underlying struct device without lock protection.

Hence, make it possible to retrieve a mutable reference to a Device from
a mutable pci::Device.

Signed-off-by: Danilo Krummrich <dakr@...nel.org>
---
 rust/kernel/pci.rs | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/rust/kernel/pci.rs b/rust/kernel/pci.rs
index 4c98b5b9aa1e..141430dac2d5 100644
--- a/rust/kernel/pci.rs
+++ b/rust/kernel/pci.rs
@@ -432,3 +432,14 @@ fn as_ref(&self) -> &device::Device {
         &self.0
     }
 }
+
+impl AsMut<device::Device> for Device {
+    fn as_mut(&mut self) -> &mut device::Device {
+        // SAFETY:
+        // - `self.0.as_raw()` is valid by the type invariant of `device::Device`,
+        // - `struct device` is embedded in `struct pci_dev`, hence it is safe to give out a
+        //    mutable reference for `device::Device` if we have a mutable reference to the
+        //    corresponding `pci::Device`.
+        unsafe { &mut *self.0.as_raw().cast() }
+    }
+}
-- 
2.43.0