[RFC PATCH 3/9] rust: usb: add usb::Device::set_interface()

[Mike Lothian]

Add a safe wrapper over `usb_set_interface()` (the standard SET_INTERFACE
request) so a Rust driver can select an interface's alternate setting
during bring-up. It blocks and sleeps, so it must be called from process
context only.

Signed-off-by: Mike Lothian <mike@xxxxxxxxxxxxxx>
Assisted-by: Claude:claude-opus-4-8 [Claude-Code]
---
 rust/kernel/usb.rs | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/rust/kernel/usb.rs b/rust/kernel/usb.rs
index e1fb50fd6997..73637e3467f1 100644
--- a/rust/kernel/usb.rs
+++ b/rust/kernel/usb.rs
@@ -605,6 +605,19 @@ pub fn control_recv(
             )
         })
     }
+
+    /// Selects alternate setting `alternate` of interface `interface`.
+    ///
+    /// Wraps [`usb_set_interface()`] (the standard `SET_INTERFACE` request). This is
+    /// a blocking, sleeping call and must only be invoked from process context.
+    ///
+    /// [`usb_set_interface()`]: https://docs.kernel.org/driver-api/usb/usb.html#c.usb_set_interface
+    pub fn set_interface(&self, interface: u8, alternate: u8) -> Result {
+        // SAFETY: `self.as_raw()` is a valid `struct usb_device` by the type invariant.
+        to_result(unsafe {
+            bindings::usb_set_interface(self.as_raw(), interface.into(), alternate.into())
+        })
+    }
 }
 
 // SAFETY: `Device` is a transparent wrapper of a type that doesn't depend on `Device`'s generic
-- 
2.54.0