From d18f3646184fc805d213fc049fc3b5d9fb9a6a27 Mon Sep 17 00:00:00 2001
From: Danilo Krummrich <dakr@kernel.org>
Date: Mon, 25 May 2026 22:21:11 +0200
Subject: [PATCH] samples: rust: rust_driver_auxiliary: showcase lifetime-bound
 registration data

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>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Link: https://patch.msgid.link/20260525202921.124698-25-dakr@kernel.org
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
         );