Re: [PATCH 4/8] rust: io: register: use path fragment in relative internal rules

[Alexandre Courbot]

On Tue Jul 21, 2026 at 4:00 AM PDT, Alexandre Courbot wrote:
> The base of a relative register is a type, but its current fragment is
> `ident`. This prevents referencing bases that are e.g. declared in
> another module.
>
> The `path` fragment is more accurate to represent relative register
> bases, but bases are currently followed by `+`, which is forbidden right
> after `path` fragments.
>
> `:` is another separator that can carry the desired semantics, and is
> legal to follow a `path` fragment. Thus, replace the `+` separator with
> `:` in the internal rules so we can change the fragment for relative
> register bases to `path`.
>
> The public rule still uses the `+` notation and an `ident` fragment, so
> there is no user-facing change yet; only a minor replumbing of the
> internals to better support the new syntax introduced in the next patch.
>
> Signed-off-by: Alexandre Courbot <acourbot@xxxxxxxxxx>
> ---
>  rust/kernel/io/register.rs | 23 ++++++++++++-----------
>  1 file changed, 12 insertions(+), 11 deletions(-)
>
> diff --git a/rust/kernel/io/register.rs b/rust/kernel/io/register.rs
> index 1e0e23e4233f..62208f52752a 100644
> --- a/rust/kernel/io/register.rs
> +++ b/rust/kernel/io/register.rs
> @@ -816,8 +816,8 @@ macro_rules! register {
>          $(
>          $crate::register!(
>              @reg $(#[$attr])* $vis $name ($storage) $([$size $(, stride = $stride)?])?
> -                $(@ $($base +)? $offset)?
> -                $(=> $alias $(+ $alias_offset)? $([$alias_idx])? )?
> +                $(@ $($base :)? $offset)?
> +                $(=> $alias $(: $alias_offset)? $([$alias_idx])? )?
>              { $($fields)* }
>          );
>          )*
> @@ -850,7 +850,7 @@ macro_rules! register {
>  
>      // Creates a register at a relative offset from a base address provider.
>      (
> -        @reg $(#[$attr:meta])* $vis:vis $name:ident ($storage:ty) @ $base:ident + $offset:literal
> +        @reg $(#[$attr:meta])* $vis:vis $name:ident ($storage:ty) @ $base:path : $offset:literal
>              { $($fields:tt)* }
>      ) => {
>          $crate::register!(@bitfield $(#[$attr])* $vis struct $name($storage) { $($fields)* });
> @@ -860,7 +860,7 @@ macro_rules! register {
>  
>      // Creates an alias register of relative offset register `alias` with its own fields.
>      (
> -        @reg $(#[$attr:meta])* $vis:vis $name:ident ($storage:ty) => $base:ident + $alias:path
> +        @reg $(#[$attr:meta])* $vis:vis $name:ident ($storage:ty) => $base:path : $alias:path
>              { $($fields:tt)* }
>      ) => {
>          $crate::register!(@bitfield $(#[$attr])* $vis struct $name($storage) { $($fields)* });
> @@ -916,7 +916,7 @@ macro_rules! register {
>      (
>          @reg $(#[$attr:meta])* $vis:vis $name:ident ($storage:ty)
>              [ $size:expr, stride = $stride:expr ]
> -            @ $base:ident + $offset:literal { $($fields:tt)* }
> +            @ $base:path : $offset:literal { $($fields:tt)* }
>      ) => {
>          $crate::build_assert::static_assert!(::core::mem::size_of::<$storage>() <= $stride);
>  
> @@ -928,11 +928,12 @@ macro_rules! register {
>      // Shortcut for contiguous array of relative registers (stride == size of element).
>      (
>          @reg $(#[$attr:meta])* $vis:vis $name:ident ($storage:ty) [ $size:expr ]
> -            @ $base:ident + $offset:literal { $($fields:tt)* }
> +            @ $base:path : $offset:literal { $($fields:tt)* }
>      ) => {
>          $crate::register!(
> -            $(#[$attr])* $vis $name($storage) [ $size, stride = ::core::mem::size_of::<$storage>() ]
> -                @ $base + $offset { $($fields)* }
> +            @reg $(#[$attr])* $vis $name($storage)

Mmm looks like this `@reg` should also have been added by the first patch.