Re: [PATCH] usb: rust: mark Device and Interface methods as inline

[Daniel Almeida <daniel.almeida@collabora.com>]

> On 16 Jun 2026, at 19:36, Nicolás Antinori <nico.antinori.7@gmail.com> wrote:
> 
> When building the kernel using llvm-19.1.7-rust-1.85.1-x86_64, the
> following symbols are generated:
> 
> $ nm vmlinux | grep ' _R'.*usb.*Device | rustfilt
> ...
> ffffffff823f2490 T <kernel::usb::Device as kernel::sync::aref::AlwaysRefCounted>::dec_ref
> ffffffff823f2470 T <kernel::usb::Device as kernel::sync::aref::AlwaysRefCounted>::inc_ref
> ...
> 
> $ nm vmlinux | grep ' _R'.*usb.*Interface | rustfilt
> ffffffff823f2450 T <kernel::usb::Interface as kernel::sync::aref::AlwaysRefCounted>::dec_ref
> ffffffff823f2430 T <kernel::usb::Interface as kernel::sync::aref::AlwaysRefCounted>::inc_ref
> ...
> 
> However, these Rust symbols are trivial wrappers around the
> `usb_get_dev`, `usb_put_dev`, `usb_get_intf` and `usb_put_intf`
> functions. It doesn't make sense to go through a trivial wrapper
> for these functions.
> 
> Link: https://github.com/Rust-for-Linux/linux/issues/1145
> Suggested-by: Alice Ryhl <aliceryhl@google.com>
> Signed-off-by: Nicolás Antinori <nico.antinori.7@gmail.com>
> ---
> rust/kernel/usb.rs | 4 ++++
> 1 file changed, 4 insertions(+)
> 
> diff --git a/rust/kernel/usb.rs b/rust/kernel/usb.rs
> index 7aff0c82d0af..efbbee319b1a 100644
> --- a/rust/kernel/usb.rs
> +++ b/rust/kernel/usb.rs
> @@ -393,6 +393,7 @@ fn as_ref(&self) -> &Device {
> 
> // SAFETY: Instances of `Interface` are always reference-counted.
> unsafe impl AlwaysRefCounted for Interface {
> +    #[inline]
>     fn inc_ref(&self) {
>         // SAFETY: The invariants of `Interface` guarantee that `self.as_raw()`
>         // returns a valid `struct usb_interface` pointer, for which we will
> @@ -400,6 +401,7 @@ fn inc_ref(&self) {
>         unsafe { bindings::usb_get_intf(self.as_raw()) };
>     }
> 
> +    #[inline]
>     unsafe fn dec_ref(obj: NonNull<Self>) {
>         // SAFETY: The safety requirements guarantee that the refcount is non-zero.
>         unsafe { bindings::usb_put_intf(obj.cast().as_ptr()) }
> @@ -444,6 +446,7 @@ fn as_raw(&self) -> *mut bindings::usb_device {
> 
> // SAFETY: Instances of `Device` are always reference-counted.
> unsafe impl AlwaysRefCounted for Device {
> +    #[inline]
>     fn inc_ref(&self) {
>         // SAFETY: The invariants of `Device` guarantee that `self.as_raw()`
>         // returns a valid `struct usb_device` pointer, for which we will
> @@ -451,6 +454,7 @@ fn inc_ref(&self) {
>         unsafe { bindings::usb_get_dev(self.as_raw()) };
>     }
> 
> +    #[inline]
>     unsafe fn dec_ref(obj: NonNull<Self>) {
>         // SAFETY: The safety requirements guarantee that the refcount is non-zero.
>         unsafe { bindings::usb_put_dev(obj.cast().as_ptr()) }
> -- 
> 2.47.3
> 
> 

Reviewed-by: Daniel Almeida <daniel.almeida@collabora.com>