[PATCH AUTOSEL 6.14 302/642] rust/faux: Add missing parent argument to Registration::new()

[PATCH AUTOSEL 6.14 302/642] rust/faux: Add missing parent argument to Registration::new()

[Sasha Levin]

From: Lyude Paul <lyude@redhat.com>

[ Upstream commit 95cb0cb546c2892b7a31ff2fce6573f201a214b8 ]

A little late in the review of the faux device interface, we added the
ability to specify a parent device when creating new faux devices - but
this never got ported over to the rust bindings. So, let's add the missing
argument now so we don't have to convert other users later down the line.

Signed-off-by: Lyude Paul <lyude@redhat.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://lore.kernel.org/r/20250227193522.198344-1-lyude@redhat.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 rust/kernel/faux.rs              | 13 +++++++++++--
 samples/rust/rust_driver_faux.rs |  2 +-
 2 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/rust/kernel/faux.rs b/rust/kernel/faux.rs
index 5acc0c02d451f..68f53edf05d70 100644
--- a/rust/kernel/faux.rs
+++ b/rust/kernel/faux.rs
@@ -24,11 +24,20 @@
 
 impl Registration {
     /// Create and register a new faux device with the given name.
-    pub fn new(name: &CStr) -> Result<Self> {
+    pub fn new(name: &CStr, parent: Option<&device::Device>) -> Result<Self> {
         // SAFETY:
         // - `name` is copied by this function into its own storage
         // - `faux_ops` is safe to leave NULL according to the C API
-        let dev = unsafe { bindings::faux_device_create(name.as_char_ptr(), null_mut(), null()) };
+        // - `parent` can be either NULL or a pointer to a `struct device`, and `faux_device_create`
+        //   will take a reference to `parent` using `device_add` - ensuring that it remains valid
+        //   for the lifetime of the faux device.
+        let dev = unsafe {
+            bindings::faux_device_create(
+                name.as_char_ptr(),
+                parent.map_or(null_mut(), |p| p.as_raw()),
+                null(),
+            )
+        };
 
         // The above function will return either a valid device, or NULL on failure
         // INVARIANT: The device will remain registered until faux_device_destroy() is called, which
diff --git a/samples/rust/rust_driver_faux.rs b/samples/rust/rust_driver_faux.rs
index 048c6cb98b29a..58a3a94121bff 100644
--- a/samples/rust/rust_driver_faux.rs
+++ b/samples/rust/rust_driver_faux.rs
@@ -20,7 +20,7 @@ impl Module for SampleModule {
     fn init(_module: &'static ThisModule) -> Result<Self> {
         pr_info!("Initialising Rust Faux Device Sample\n");
 
-        let reg = faux::Registration::new(c_str!("rust-faux-sample-device"))?;
+        let reg = faux::Registration::new(c_str!("rust-faux-sample-device"), None)?;
 
         dev_info!(reg.as_ref(), "Hello from faux device!\n");
 
-- 
2.39.5

Re: [PATCH AUTOSEL 6.14 302/642] rust/faux: Add missing parent argument to Registration::new()

[Miguel Ojeda]

On Tue, May 6, 2025 at 12:26 AM Sasha Levin <sashal@kernel.org> wrote:
>
> From: Lyude Paul <lyude@redhat.com>
>
> [ Upstream commit 95cb0cb546c2892b7a31ff2fce6573f201a214b8 ]
>
> A little late in the review of the faux device interface, we added the
> ability to specify a parent device when creating new faux devices - but
> this never got ported over to the rust bindings. So, let's add the missing
> argument now so we don't have to convert other users later down the line.
>
> Signed-off-by: Lyude Paul <lyude@redhat.com>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Link: https://lore.kernel.org/r/20250227193522.198344-1-lyude@redhat.com
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Signed-off-by: Sasha Levin <sashal@kernel.org>

Does someone need this in 6.14.y?

Thanks!

Cheers,
Miguel