Re: [PATCH v2 1/2] rust: macros: Add derive Display for enums

["Benno Lossin" <lossin@kernel.org>]

On Sun Jan 4, 2026 at 9:07 PM CET, Maurice Hieronymus wrote:
> Add a derive macro that implements kernel::fmt::Display for enums.
> The macro outputs the exact variant name as written, preserving case.
>
> This supports all enum variant types: unit, tuple, and struct variants.
> For variants with data, only the variant name is displayed.

I don't think we should be adding this. Display is designed for
user-facing output and so it should always be carefully designed and no
automation should exist for it.

The use-case in the second patch is also much better served by either a
manual match on the enum:

    impl fmt::Display for Chipset {
        fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
            match self {
                Chipset::Variant => write!(f, "Variant"),
                // ...
            }
        }
    }

Or by adding the respective code in the declarative macro already used
to define it.

Cheers,
Benno

> Signed-off-by: Maurice Hieronymus <mhi@mailbox.org>
> ---
>  rust/macros/display.rs | 52 ++++++++++++++++++++++++++++++++++++++++++
>  rust/macros/lib.rs     | 42 ++++++++++++++++++++++++++++++++++
>  2 files changed, 94 insertions(+)
>  create mode 100644 rust/macros/display.rs