Subject: Re: linux-next: build failure after merge of the rust tree

From: Alice Ryhl <[email-masked]>
Date: Mon, 17 Nov 2025 14:51:04 +0000

On Mon, Nov 17, 2025 at 07:04:17PM +1100, Stephen Rothwell wrote:
> Hi all,
> 
> After merging the rust tree, today's linux-next build (x86_64
> allmodconfig) failed like this:
> 
> error[E0277]: `Chipset` doesn't implement `core::fmt::Display`
>    --> drivers/gpu/nova-core/gpu.rs:233:13
>     |
> 233 |             self.chipset,
>     |             ^^^^^^^^^^^^ `Chipset` cannot be formatted with the default formatter
>     |
>     = help: the trait `core::fmt::Display` is not implemented for `Chipset`
>     = note: in format strings you may be able to use `{:?}` (or {:#?} for pretty-print) instead
>     = note: this error originates in the macro `$crate::format_args` which comes from the expansion of the macro `write` (in Nightly builds, run with -Z macro-backtrace for more info)
> 
> error[E0277]: `Revision` doesn't implement `core::fmt::Display`
>    --> drivers/gpu/nova-core/gpu.rs:235:13
>     |
> 235 |             self.revision
>     |             ^^^^^^^^^^^^^ `Revision` cannot be formatted with the default formatter
>     |
>     = help: the trait `core::fmt::Display` is not implemented for `Revision`
>     = note: in format strings you may be able to use `{:?}` (or {:#?} for pretty-print) instead
>     = note: this error originates in the macro `$crate::format_args` which comes from the expansion of the macro `write` (in Nightly builds, run with -Z macro-backtrace for more info)
> 
> error[E0277]: the trait bound `MsgFunction: kernel::fmt::Display` is not satisfied
>    --> drivers/gpu/nova-core/gsp/cmdq.rs:532:9
>     |
> 532 | /         dev_dbg!(
> 533 | |             &self.dev,
> 534 | |             "GSP RPC: send: seq# {}, function={}, length=0x{:x}\n",
>     | |                                               -- required by a bound introduced by this call
> 535 | |             self.seq,
> 536 | |             M::FUNCTION,
> 537 | |             dst.header.length(),
> 538 | |         );
>     | |_________^ the trait `kernel::fmt::Display` is not implemented for `MsgFunction`
>     |
>     = help: the following other types implement trait `kernel::fmt::Display`:
>               &T
>               Arc<T>
>               Arguments<'_>
>               BStr
>               Box<T, A>
>               CStr
>               Chipset
>               Class
>             and 22 others
>     = note: required for `kernel::fmt::Adapter<&MsgFunction>` to implement `core::fmt::Display`
> note: required by a bound in `core::fmt::rt::Argument::<'_>::new_display`
>    --> /usr/lib/rustlib/src/rust/library/core/src/fmt/rt.rs:113:27
>     |
> 113 |     pub fn new_display<T: Display>(x: &T) -> Argument<'_> {
>     |                           ^^^^^^^ required by this bound in `Argument::<'_>::new_display`
>     = note: this error originates in the macro `::core::format_args` which comes from the expansion of the macro `dev_dbg` (in Nightly builds, run with -Z macro-backtrace for more info)
> 
> error: aborting due to 3 previous errors
> 
> For more information about this error, try `rustc --explain E0277`.
> 
> Caused by commit
> 
>   c5cf01ba8dfe ("rust: support formatting of foreign types")
> 
> (I think) interacting with commits
> 
>   38b7cc448a5b ("gpu: nova-core: implement Display for Spec")
>   75f6b1de8133 ("gpu: nova-core: gsp: Add GSP command queue bindings and handling")
> 
> from the drm-rust tree.

I applied a patch to drm-rust-next that makes this error go away.

Alice