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>

diff --git a/samples/rust/rust_driver_auxiliary.rs b/samples/rust/rust_driver_auxiliary.rs
index e3e811a14110c4a029780d03a6ed1e6f13717c1e..2c1351040e45e5139f607e940b49aafeff943e1c 100644 (file)
--- a/samples/rust/rust_driver_auxiliary.rs
+++ b/samples/rust/rust_driver_auxiliary.rs
@@ -51,16 +51,17 @@ impl auxiliary::Driver for AuxiliaryDriver {
     }
 }
 
-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 @@ impl pci::Driver for ParentDriver {
         _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 @@ impl ParentDriver {
         );
 
         dev_info!(
-            dev,
+            pdev,
             "Connected to auxiliary device with index {}.\n",
             data.index
         );