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2026-09-03rust: io: register: reimplement as proc macroGary Guo
The existing `register!` macro is implemented as a declarative macro. Reimplement it as proc macro instead, with no functional changes intended. The old implementation produces unhelpful diagnostics when things go wrong. For example, for code like register! { pub(crate) TESTREG(u32) { 31:0 data; } } which misses out the "@ offset" part of the specification, and the following error is produced: error: no rules expected `{` --> test.rs:42:5 | 42 | / register! { 43 | | pub(crate) TESTREG(u32) { 44 | | 31:0 data; ... | 100 | | } | |_____^ no rules expected this token in macro call which isn't very helpful. With the proc macro implementation, the following error is produced: error: expected `@` or `=>` --> tests.rs:43:33 | 43 | pub(crate) TESTREG(u32) { | ^ which is much more helpful. Apart from diagnostics, proc macro also has a benefit of not having follow-set restrictions, which makes syntax like register!(name: ty @ offset); possible; declarative macro will reject this as `@` is not in the follow-set of "ty" metavariable kind. Signed-off-by: Gary Guo <gary@garyguo.net> Reviewed-by: Alexandre Courbot <acourbot@nvidia.com> Tested-by: Alexandre Courbot <acourbot@nvidia.com> Link: https://patch.msgid.link/20260901-typed_register-v4-1-5552b1d59525@garyguo.net [ Fix typo in module-level doc comment and fix ArrayDef syntax description to match the actual macro syntax. - Danilo ] Signed-off-by: Danilo Krummrich <dakr@kernel.org>