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

Tamir Duberstein
2025-11-17T15:37:47Z

On Mon, Nov 17, 2025 at 9:51 AM Alice Ryhl <aliceryhl@google.com> wrote:
>
> 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

Thanks for taking care of this!

Alexandre: the correct thing to do going forward is never to use
`core::fmt`; instead always use `kernel::fmt`.