linux-kernel - [PATCH 3/8] rust: auxiliary: consider auxiliary devices always have a parent

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Message-ID: <20251020223516.241050-4-dakr@kernel.org>
Date: Tue, 21 Oct 2025 00:34:25 +0200
From: Danilo Krummrich <dakr@...nel.org>
To: gregkh@...uxfoundation.org,
	rafael@...nel.org,
	bhelgaas@...gle.com,
	kwilczynski@...nel.org,
	david.m.ertman@...el.com,
	ira.weiny@...el.com,
	leon@...nel.org,
	acourbot@...dia.com,
	ojeda@...nel.org,
	alex.gaynor@...il.com,
	boqun.feng@...il.com,
	gary@...yguo.net,
	bjorn3_gh@...tonmail.com,
	lossin@...nel.org,
	a.hindborg@...nel.org,
	aliceryhl@...gle.com,
	tmgross@...ch.edu,
	pcolberg@...hat.com
Cc: rust-for-linux@...r.kernel.org,
	linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Danilo Krummrich <dakr@...nel.org>
Subject: [PATCH 3/8] rust: auxiliary: consider auxiliary devices always have a parent

An auxiliary device is guaranteed to always have a parent device (both
in C and Rust), hence don't return an Option<&auxiliary::Device> in
auxiliary::Device::parent().

Signed-off-by: Danilo Krummrich <dakr@...nel.org>
---
 drivers/gpu/drm/nova/file.rs          | 2 +-
 rust/kernel/auxiliary.rs              | 7 ++++---
 samples/rust/rust_driver_auxiliary.rs | 2 +-
 3 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/nova/file.rs b/drivers/gpu/drm/nova/file.rs
index 90b9d2d0ec4a..a3b7bd36792c 100644
--- a/drivers/gpu/drm/nova/file.rs
+++ b/drivers/gpu/drm/nova/file.rs
@@ -28,7 +28,7 @@ pub(crate) fn get_param(
         _file: &drm::File<File>,
     ) -> Result<u32> {
         let adev = &dev.adev;
-        let parent = adev.parent().ok_or(ENOENT)?;
+        let parent = adev.parent();
         let pdev: &pci::Device = parent.try_into()?;
 
         let value = match getparam.param as u32 {
diff --git a/rust/kernel/auxiliary.rs b/rust/kernel/auxiliary.rs
index a6a2b23befce..e5bddb738d58 100644
--- a/rust/kernel/auxiliary.rs
+++ b/rust/kernel/auxiliary.rs
@@ -215,9 +215,10 @@ pub fn id(&self) -> u32 {
         unsafe { (*self.as_raw()).id }
     }
 
-    /// Returns a reference to the parent [`device::Device`], if any.
-    pub fn parent(&self) -> Option<&device::Device> {
-        self.as_ref().parent()
+    /// Returns a reference to the parent [`device::Device`].
+    pub fn parent(&self) -> &device::Device {
+        // SAFETY: A `struct auxiliary_device` always has a parent.
+        unsafe { self.as_ref().parent().unwrap_unchecked() }
     }
 }
 
diff --git a/samples/rust/rust_driver_auxiliary.rs b/samples/rust/rust_driver_auxiliary.rs
index 0e221abe4936..2e9afeb83d4f 100644
--- a/samples/rust/rust_driver_auxiliary.rs
+++ b/samples/rust/rust_driver_auxiliary.rs
@@ -68,7 +68,7 @@ fn probe(pdev: &pci::Device<Core>, _info: &Self::IdInfo) -> impl PinInit<Self, E
 
 impl ParentDriver {
     fn connect(adev: &auxiliary::Device) -> Result<()> {
-        let parent = adev.parent().ok_or(EINVAL)?;
+        let parent = adev.parent();
         let pdev: &pci::Device = parent.try_into()?;
 
         let vendor = pdev.vendor_id();
-- 
2.51.0