From 0242623384c767b1156b61b67894b4ecf6682b8b Mon Sep 17 00:00:00 2001
From: Danilo Krummrich <dakr@kernel.org>
Date: Thu, 16 Oct 2025 14:55:28 +0200
Subject: rust: driver: let probe() return impl PinInit<Self, Error>

The driver model defines the lifetime of the private data stored in (and
owned by) a bus device to be valid from when the driver is bound to a
device (i.e. from successful probe()) until the driver is unbound from
the device.

This is already taken care of by the Rust implementation of the driver
model. However, we still ask drivers to return a Result<Pin<KBox<Self>>>
from probe().

Unlike in C, where we do not have the concept of initializers, but
rather deal with uninitialized memory, drivers can just return an
impl PinInit<Self, Error> instead.

This contributes to more clarity to the fact that a driver returns it's
device private data in probe() and the Rust driver model owns the data,
manages the lifetime and - considering the lifetime - provides (safe)
accessors for the driver.

Hence, let probe() functions return an impl PinInit<Self, Error> instead
of Result<Pin<KBox<Self>>>.

Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
---
 samples/rust/rust_driver_pci.rs | 53 ++++++++++++++++++++---------------------
 1 file changed, 26 insertions(+), 27 deletions(-)

(limited to 'samples/rust/rust_driver_pci.rs')

diff --git a/samples/rust/rust_driver_pci.rs b/samples/rust/rust_driver_pci.rs
index 55a683c39ed9..5823787bea8e 100644
--- a/samples/rust/rust_driver_pci.rs
+++ b/samples/rust/rust_driver_pci.rs
@@ -65,35 +65,34 @@ impl pci::Driver for SampleDriver {
 
     const ID_TABLE: pci::IdTable<Self::IdInfo> = &PCI_TABLE;
 
-    fn probe(pdev: &pci::Device<Core>, info: &Self::IdInfo) -> Result<Pin<KBox<Self>>> {
-        let vendor = pdev.vendor_id();
-        dev_dbg!(
-            pdev.as_ref(),
-            "Probe Rust PCI driver sample (PCI ID: {}, 0x{:x}).\n",
-            vendor,
-            pdev.device_id()
-        );
-
-        pdev.enable_device_mem()?;
-        pdev.set_master();
-
-        let drvdata = KBox::pin_init(
-            try_pin_init!(Self {
+    fn probe(pdev: &pci::Device<Core>, info: &Self::IdInfo) -> impl PinInit<Self, Error> {
+        pin_init::pin_init_scope(move || {
+            let vendor = pdev.vendor_id();
+            dev_dbg!(
+                pdev.as_ref(),
+                "Probe Rust PCI driver sample (PCI ID: {}, 0x{:x}).\n",
+                vendor,
+                pdev.device_id()
+            );
+
+            pdev.enable_device_mem()?;
+            pdev.set_master();
+
+            Ok(try_pin_init!(Self {
                 bar <- pdev.iomap_region_sized::<{ Regs::END }>(0, c_str!("rust_driver_pci")),
-                pdev: pdev.into(),
                 index: *info,
-            }),
-            GFP_KERNEL,
-        )?;
-
-        let bar = drvdata.bar.access(pdev.as_ref())?;
-        dev_info!(
-            pdev.as_ref(),
-            "pci-testdev data-match count: {}\n",
-            Self::testdev(info, bar)?
-        );
-
-        Ok(drvdata)
+                _: {
+                    let bar = bar.access(pdev.as_ref())?;
+
+                    dev_info!(
+                        pdev.as_ref(),
+                        "pci-testdev data-match count: {}\n",
+                        Self::testdev(info, bar)?
+                    );
+                },
+                pdev: pdev.into(),
+            }))
+        })
     }
 
     fn unbind(pdev: &pci::Device<Core>, this: Pin<&Self>) {
-- 
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