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

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

[Alice Ryhl]

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.")
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,
-- 
Alice Ryhl <aliceryhl@google.com>

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

[Miguel Ojeda]

On Thu, Jul 16, 2026 at 12:22 PM Alice Ryhl <aliceryhl@google.com> 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.")
> Link: https://github.com/rust-lang/rust/issues/79813
> Signed-off-by: Alice Ryhl <aliceryhl@google.com>

I was doubly surprised since upstream made it a warning by default a
long time ago, and yet we didn't see it; and since I hadn't seen in my
CI even yesterday.

It turns out this just landed into today's nightly:

Link: https://github.com/rust-lang/rust/pull/159222

  The semicolon_in_expressions_from_macros lint previously
  suppressed warnings about non-local macros. This masks
  a lint that will subsequently become a hard error.

So that explains it. And this is the one that will make it a hard error:

Link: https://github.com/rust-lang/rust/pull/159218

Ok, I will land this into `rust-fixes` then, and send the PR during
the weekend after tomorrow's -next.

Cheers,
Miguel

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

[Danilo Krummrich]

On Thu Jul 16, 2026 at 2:17 PM CEST, Miguel Ojeda wrote:
> Ok, I will land this into `rust-fixes` then, and send the PR during
> the weekend after tomorrow's -next.

I can also take it through driver-core-fixes, I have another minor fix to send
anyway.

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

[Miguel Ojeda]

On Thu, Jul 16, 2026 at 3:48 PM Danilo Krummrich <dakr@kernel.org> wrote:
>
> I can also take it through driver-core-fixes, I have another minor fix to send
> anyway.

Thanks, no worries, I will take it -- this kind of fix makes more
sense in `rust-fixes` since they are treewide, i.e. it could have
triggered in more places at the same time since they changer the
compiler, and I have other few in the branch accumulated for Rust
1.99.0.

(An Acked-by is always nice of course!)

Cheers,
Miguel

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

[Gary Guo]

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,

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

[Miguel Ojeda]

On Thu, Jul 16, 2026 at 4:00 PM Gary Guo <gary@garyguo.net> wrote:
>
> 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).

Yeah, normally I don't put that tag for these, because there is no
actual bug being fixed.

Instead, I normally say something like:

Cc: stable@vger.kernel.org # Needed in 6.12.y and later (Rust is
pinned in older LTSs).

I will do that.

Cheers,
Miguel