Re: [PATCH] rust: device: avoid trailing ; in printing macros

["Gary Guo" <gary@garyguo.net>]

On Thu Jul 16, 2026 at 11:22 AM BST, Alice Ryhl wrote:
> These macros are used like expressions, so they should must not emit a
> semicolon. This is being turned into a hard error in a future release of
> Rust.
>
> error: trailing semicolon in macro used in expression position
>   --> drivers/gpu/nova-core/firmware/fsp.rs:79:34
>    |
> 79 |                 .inspect_err(|_| dev_err!(dev, "FMC firmware missing '{}' section\n", name))
>    |                                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>    |
>    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
>    = note: for more information, see issue #79813 <https://github.com/rust-lang/rust/issues/79813>
>    = note: this error originates in the macro `dev_err` (in Nightly builds, run with -Z macro-backtrace for more info)
>
> Cc: stable@vger.kernel.org
> Fixes: 5c7ca6fa603f ("rust: add `dev_*` print macros.")

I suppose this can also be argued to be a fix to the user that use them in
non-statement positions (by saying that original implementation is for
statement-position only and expression-position usage is an improvement).

But either way:

Reviewed-by: Gary Guo <gary@garyguo.net>

Best,
Gary

> Link: https://github.com/rust-lang/rust/issues/79813
> Signed-off-by: Alice Ryhl <aliceryhl@google.com>
> ---
>  rust/kernel/device.rs | 20 +++++++++-----------
>  1 file changed, 9 insertions(+), 11 deletions(-)
>
> diff --git a/rust/kernel/device.rs b/rust/kernel/device.rs
> index 645afc49a27d..1a38b3bbdfb7 100644
> --- a/rust/kernel/device.rs
> +++ b/rust/kernel/device.rs
> @@ -708,9 +708,7 @@ macro_rules! impl_device_context_into_aref {
>  #[macro_export]
>  macro_rules! dev_printk {
>      ($method:ident, $dev:expr, $($f:tt)*) => {
> -        {
> -            $crate::device::Device::$method($dev.as_ref(), $crate::prelude::fmt!($($f)*))
> -        }
> +        $crate::device::Device::$method($dev.as_ref(), $crate::prelude::fmt!($($f)*))
>      }
>  }
>  
> @@ -737,7 +735,7 @@ macro_rules! dev_printk {
>  /// ```
>  #[macro_export]
>  macro_rules! dev_emerg {
> -    ($($f:tt)*) => { $crate::dev_printk!(pr_emerg, $($f)*); }
> +    ($($f:tt)*) => { $crate::dev_printk!(pr_emerg, $($f)*) }
>  }
>  
>  /// Prints an alert-level message (level 1) prefixed with device information.
> @@ -763,7 +761,7 @@ macro_rules! dev_emerg {
>  /// ```
>  #[macro_export]
>  macro_rules! dev_alert {
> -    ($($f:tt)*) => { $crate::dev_printk!(pr_alert, $($f)*); }
> +    ($($f:tt)*) => { $crate::dev_printk!(pr_alert, $($f)*) }
>  }
>  
>  /// Prints a critical-level message (level 2) prefixed with device information.
> @@ -789,7 +787,7 @@ macro_rules! dev_alert {
>  /// ```
>  #[macro_export]
>  macro_rules! dev_crit {
> -    ($($f:tt)*) => { $crate::dev_printk!(pr_crit, $($f)*); }
> +    ($($f:tt)*) => { $crate::dev_printk!(pr_crit, $($f)*) }
>  }
>  
>  /// Prints an error-level message (level 3) prefixed with device information.
> @@ -815,7 +813,7 @@ macro_rules! dev_crit {
>  /// ```
>  #[macro_export]
>  macro_rules! dev_err {
> -    ($($f:tt)*) => { $crate::dev_printk!(pr_err, $($f)*); }
> +    ($($f:tt)*) => { $crate::dev_printk!(pr_err, $($f)*) }
>  }
>  
>  /// Prints a warning-level message (level 4) prefixed with device information.
> @@ -841,7 +839,7 @@ macro_rules! dev_err {
>  /// ```
>  #[macro_export]
>  macro_rules! dev_warn {
> -    ($($f:tt)*) => { $crate::dev_printk!(pr_warn, $($f)*); }
> +    ($($f:tt)*) => { $crate::dev_printk!(pr_warn, $($f)*) }
>  }
>  
>  /// Prints a notice-level message (level 5) prefixed with device information.
> @@ -867,7 +865,7 @@ macro_rules! dev_warn {
>  /// ```
>  #[macro_export]
>  macro_rules! dev_notice {
> -    ($($f:tt)*) => { $crate::dev_printk!(pr_notice, $($f)*); }
> +    ($($f:tt)*) => { $crate::dev_printk!(pr_notice, $($f)*) }
>  }
>  
>  /// Prints an info-level message (level 6) prefixed with device information.
> @@ -893,7 +891,7 @@ macro_rules! dev_notice {
>  /// ```
>  #[macro_export]
>  macro_rules! dev_info {
> -    ($($f:tt)*) => { $crate::dev_printk!(pr_info, $($f)*); }
> +    ($($f:tt)*) => { $crate::dev_printk!(pr_info, $($f)*) }
>  }
>  
>  /// Prints a debug-level message (level 7) prefixed with device information.
> @@ -919,5 +917,5 @@ macro_rules! dev_info {
>  /// ```
>  #[macro_export]
>  macro_rules! dev_dbg {
> -    ($($f:tt)*) => { $crate::dev_printk!(pr_dbg, $($f)*); }
> +    ($($f:tt)*) => { $crate::dev_printk!(pr_dbg, $($f)*) }
>  }
>
> ---
> base-commit: a13c140cc289c0b7b3770bce5b3ad42ab35074aa
> change-id: 20260716-device-trail-semicolon-1c02e29ea1cf
>
> Best regards,