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

Danilo Krummrich
2025-10-20T22:35:47Z

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@kernel.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