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From: Danilo Krummrich <dakr@kernel.org>
To: gregkh@linuxfoundation.org, rafael@kernel.org, acourbot@nvidia.com,
 aliceryhl@google.com, david.m.ertman@intel.com, ira.weiny@intel.com,
 leon@kernel.org, viresh.kumar@linaro.org, m.wilczynski@samsung.com,
 ukleinek@kernel.org, bhelgaas@google.com, kwilczynski@kernel.org,
 abdiel.janulgue@gmail.com, robin.murphy@arm.com, markus.probst@posteo.de,
 ojeda@kernel.org, boqun@kernel.org, gary@garyguo.net,
 bjorn3_gh@protonmail.com, lossin@kernel.org, a.hindborg@kernel.org,
 tmgross@umich.edu, igor.korotin@linux.dev, daniel.almeida@collabora.com,
 pcolberg@redhat.com
Cc: driver-core@lists.linux.dev, linux-kernel@vger.kernel.org,
 nova-gpu@lists.linux.dev, dri-devel@lists.freedesktop.org,
 linux-pm@vger.kernel.org, linux-pwm@vger.kernel.org,
 linux-pci@vger.kernel.org, rust-for-linux@vger.kernel.org,
 Danilo Krummrich <dakr@kernel.org>, Eliot Courtney <ecourtney@nvidia.com>
Subject: [PATCH v4 23/27] samples: rust: rust_driver_auxiliary: showcase
 lifetime-bound registration data
Date: Fri, 22 May 2026 01:34:49 +0200
Message-ID: <20260521233501.1191842-24-dakr@kernel.org>
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Make the Data struct lifetime-parameterized, storing a reference to the
parent pci::Device<Bound>. This demonstrates that registration data can
hold device resources tied to the parent driver's lifetime.

In connect(), retrieve the parent PCI device from the registration data
rather than casting through adev.parent().

Reviewed-by: Eliot Courtney <ecourtney@nvidia.com>
Reviewed-by: Gary Guo <gary@garyguo.net>
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
---
 samples/rust/rust_driver_auxiliary.rs | 58 ++++++++++++++++-----------
 1 file changed, 35 insertions(+), 23 deletions(-)

diff --git a/samples/rust/rust_driver_auxiliary.rs b/samples/rust/rust_driver_auxiliary.rs
index e3e811a14110..2c1351040e45 100644
--- a/samples/rust/rust_driver_auxiliary.rs
+++ b/samples/rust/rust_driver_auxiliary.rs
@@ -51,16 +51,17 @@ fn probe<'bound>(
     }
 }
 
-struct Data {
+struct Data<'bound> {
     index: u32,
+    parent: &'bound pci::Device<Bound>,
 }
 
 struct ParentDriver;
 
 #[allow(clippy::type_complexity)]
 struct ParentData<'bound> {
-    _reg0: auxiliary::Registration<'bound, ForLt!(Data)>,
-    _reg1: auxiliary::Registration<'bound, ForLt!(Data)>,
+    _reg0: auxiliary::Registration<'bound, ForLt!(Data<'_>)>,
+    _reg1: auxiliary::Registration<'bound, ForLt!(Data<'_>)>,
 }
 
 kernel::pci_device_table!(
@@ -81,33 +82,44 @@ fn probe<'bound>(
         _info: &'bound Self::IdInfo,
     ) -> impl PinInit<Self::Data<'bound>, Error> + 'bound {
         Ok(ParentData {
-            _reg0: auxiliary::Registration::new(
-                pdev.as_ref(),
-                AUXILIARY_NAME,
-                0,
-                MODULE_NAME,
-                Data { index: 0 },
-            )?,
-            _reg1: auxiliary::Registration::new(
-                pdev.as_ref(),
-                AUXILIARY_NAME,
-                1,
-                MODULE_NAME,
-                Data { index: 1 },
-            )?,
+            // SAFETY: `ParentData` is the driver's private data, which is dropped when the
+            // device is unbound; i.e. `mem::forget()` is never called on it.
+            _reg0: unsafe {
+                auxiliary::Registration::new_with_lt(
+                    pdev.as_ref(),
+                    AUXILIARY_NAME,
+                    0,
+                    MODULE_NAME,
+                    Data {
+                        index: 0,
+                        parent: pdev,
+                    },
+                )?
+            },
+            // SAFETY: See `_reg0` above.
+            _reg1: unsafe {
+                auxiliary::Registration::new_with_lt(
+                    pdev.as_ref(),
+                    AUXILIARY_NAME,
+                    1,
+                    MODULE_NAME,
+                    Data {
+                        index: 1,
+                        parent: pdev,
+                    },
+                )?
+            },
         })
     }
 }
 
 impl ParentDriver {
     fn connect(adev: &auxiliary::Device<Bound>) -> Result {
-        let dev = adev.parent();
-        let pdev: &pci::Device<Bound> = dev.try_into()?;
-
-        let data = adev.registration_data::<ForLt!(Data)>()?;
+        let data = adev.registration_data::<ForLt!(Data<'_>)>()?;
+        let pdev = data.parent;
 
         dev_info!(
-            dev,
+            pdev,
             "Connect auxiliary {} with parent: VendorID={}, DeviceID={:#x}\n",
             adev.id(),
             pdev.vendor_id(),
@@ -115,7 +127,7 @@ fn connect(adev: &auxiliary::Device<Bound>) -> Result {
         );
 
         dev_info!(
-            dev,
+            pdev,
             "Connected to auxiliary device with index {}.\n",
             data.index
         );
-- 
2.54.0