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_debugfs.rs | 21 +++++++++++----------
 1 file changed, 11 insertions(+), 10 deletions(-)

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

diff --git a/samples/rust/rust_debugfs.rs b/samples/rust/rust_debugfs.rs
index 82b61a15a34b..d3f50f344856 100644
--- a/samples/rust/rust_debugfs.rs
+++ b/samples/rust/rust_debugfs.rs
@@ -106,16 +106,17 @@ impl platform::Driver for RustDebugFs {
     fn probe(
         pdev: &platform::Device<Core>,
         _info: Option<&Self::IdInfo>,
-    ) -> Result<Pin<KBox<Self>>> {
-        let result = KBox::try_pin_init(RustDebugFs::new(pdev), GFP_KERNEL)?;
-        // We can still mutate fields through the files which are atomic or mutexed:
-        result.counter.store(91, Ordering::Relaxed);
-        {
-            let mut guard = result.inner.lock();
-            guard.x = guard.y;
-            guard.y = 42;
-        }
-        Ok(result)
+    ) -> impl PinInit<Self, Error> {
+        RustDebugFs::new(pdev).pin_chain(|this| {
+            this.counter.store(91, Ordering::Relaxed);
+            {
+                let mut guard = this.inner.lock();
+                guard.x = guard.y;
+                guard.y = 42;
+            }
+
+            Ok(())
+        })
     }
 }
 
-- 
cgit v1.2.3


From 52af0c37964be5a685cfd7aa4127bdd29d629cc7 Mon Sep 17 00:00:00 2001
From: Danilo Krummrich <dakr@kernel.org>
Date: Wed, 22 Oct 2025 16:30:42 +0200
Subject: samples: rust: debugfs: add example for blobs

Extend the Rust debugfs sample to demonstrate usage of binary file
support. The example now shows how to expose both fixed-size arrays
and dynamically sized vectors as binary blobs in debugfs.

Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Matthew Maurer <mmaurer@google.com>
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
---
 samples/rust/rust_debugfs.rs | 13 +++++++++++++
 1 file changed, 13 insertions(+)

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

diff --git a/samples/rust/rust_debugfs.rs b/samples/rust/rust_debugfs.rs
index d3f50f344856..c45b568d951b 100644
--- a/samples/rust/rust_debugfs.rs
+++ b/samples/rust/rust_debugfs.rs
@@ -38,6 +38,7 @@ use kernel::c_str;
 use kernel::debugfs::{Dir, File};
 use kernel::new_mutex;
 use kernel::prelude::*;
+use kernel::sizes::*;
 use kernel::sync::Mutex;
 
 use kernel::{acpi, device::Core, of, platform, str::CString, types::ARef};
@@ -62,6 +63,10 @@ struct RustDebugFs {
     counter: File<AtomicUsize>,
     #[pin]
     inner: File<Mutex<Inner>>,
+    #[pin]
+    array_blob: File<Mutex<[u8; 4]>>,
+    #[pin]
+    vector_blob: File<Mutex<KVec<u8>>>,
 }
 
 #[derive(Debug)]
@@ -144,6 +149,14 @@ impl RustDebugFs {
                 ),
                 counter <- Self::build_counter(&debugfs),
                 inner <- Self::build_inner(&debugfs),
+                array_blob <- debugfs.read_write_binary_file(
+                    c_str!("array_blob"),
+                    new_mutex!([0x62, 0x6c, 0x6f, 0x62]),
+                ),
+                vector_blob <- debugfs.read_write_binary_file(
+                    c_str!("vector_blob"),
+                    new_mutex!(kernel::kvec!(0x42; SZ_4K)?),
+                ),
                 _debugfs: debugfs,
                 pdev: pdev.into(),
             }
-- 
cgit v1.2.3