[PATCH v9 00/10] rust: add `register!` macro

[Alexandre Courbot <acourbot@nvidia.com>]

Further refinements on the latest design. The most relevant change is
probably the renaming of `write_val` into `write_reg` and its
specialization for register types. All the other, more minor feedback
has also been addressed.

This revision is based on `driver-core-next` as of 2026-03-09. The top
patch also depends on `drm-rust-next`, but it is only here to illustrate
what client code looks like.

A tree with this series and its dependencies is available at [1].

[1] https://github.com/Gnurou/linux/tree/b4/register

Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>

---
Changes in v9:
- Make `IoLoc::offset` take `self` by value.
- Move `IntoIoVal`'s generic argument into associated types.
- Rename `IntoIoVal` into `LocatedRegister` and make it exclusive to
  registers.
- Add missing `#[inline(always)]` statements.
- Move some of the `register!` documentation to the module level.
- Publicly export `register!` and `kernel::io` and use this reference in
  the code.
- Properly format imports in doc examples.
- Re-word note about race conditions of the `update` and `try_update`
  methods.
- Fix build error in nova-core port to the new macro.
- Link to v8: https://patch.msgid.link/20260310-register-v8-0-424f80dd43bc@nvidia.com

Changes in v8:
- Use two-arguments `Io::write` with a convenience single-argument
  `Io::write_val`.
- Remove the `IoWrite` type, all helper methods of `IoLoc`, and stop
  relying on closures to write values.
- Add traits for specifying relative and array register locations.
- Improved documentation and examples.
- Link to v7: https://patch.msgid.link/20260224-register-v7-0-aad44f760f33@nvidia.com

Changes in v7:
- Use `RES + SHIFT >= N` instead of `RES >= N - SHIFT` in
  `Bounded::shr`.
- Rename `IoRef` to `IoLoc` and all related types
  accordingly.
- Use `Into` trait bounds in both directions on `IoLoc`.
- Add RFC patch allowing fixed register values to be used directly with
  `write`.
- Link to v6: https://patch.msgid.link/20260216-register-v6-0-eec9a4de9e9e@nvidia.com

Changes in v6:
- Remove Tested-by tags as the code has considerably changed.
- Make `Bounded::get` const so it can be used with registers.
- Use the `pin_init::zeroed()` const function instead of defining our
  own method.
- Generalize all `Io` around the new `IoRef` and `IoWrite` types, and
  make registers use these as well.
- Use the more natural pattern of having the `Io` type perform the I/O
  access instead of the register type.
- Convert the whole PCI driver example, and not only the PCI
  configuration space.
- Rename `Bounded::as_bool` to `Bounded::into_bool`.
- Drop `Bounded::into_inner` in favor of making `Bounded::get` const.
- Link to v5: https://patch.msgid.link/20260129-register-v5-0-c4587c902514@nvidia.com

Changes in v5:
- Rename all setters to `with_*` and `with_const_*`.
- Use `, stride = ` to specify the stride of register arrays.
- Remove `Deref` requirement on the `RegisterIo` trait and make it
  `#[doc(hidden)`.
- Simplify the top dispatch rule a bit.
- Link to v4: https://patch.msgid.link/20260128-register-v4-0-aee3a33d9649@nvidia.com

Changes in v4:
- Add `with_` const field setter methods (removing the need to call
  `Bounded::new` for constant field values).
- Add `into_inner` const method for `Bounded`.
- Add `from_raw` and const `zeroed` method to create initial register
  values.
- More documentation improvements.
- Link to v3: https://patch.msgid.link/20260126-register-v3-0-2328a59d7312@nvidia.com

Changes in v3:
- Sort the Rust features list alphabetically.
- Rebase on top of latest `driver-core-next` including the new Io trait.
- Allow several registers to be defined from the same macro invocation.
- Remove references to `bitfield!` macro.
- Fix doccomment of `shr` and `shl`.
- Use `+` syntax for relative register offsets.
- Move register arrays size and stride to after the backing type declaration.
- Use regular doccomments to document registers and fields (thanks Gary!).
- Remove `Default` implementation and implement the more predictable
  `Zeroable` instead.
- Improve doccomments a bit.
- Link to v2: https://patch.msgid.link/20260121-register-v2-0-79d9b8d5e36a@nvidia.com

Changes in v2:
- Remove `bitfield!` and put its rules into `register!` to give it more
  time to get reviewed.
- Allow output type larger than strictly required for `shr` and `shl` on
  `Bounded`.
- Enable the `generic_arg_infer` feature, required for rustc < 1.89.
- Link to v1: https://patch.msgid.link/20260120-register-v1-0-723a1743b557@nvidia.com

---
Alexandre Courbot (10):
      rust: enable the `generic_arg_infer` feature
      rust: num: add `shr` and `shl` methods to `Bounded`
      rust: num: add `into_bool` method to `Bounded`
      rust: num: make Bounded::get const
      rust: io: add IoLoc type and generic I/O accessors
      rust: io: use generic read/write accessors for primitive accesses
      rust: io: add `register!` macro
      rust: io: introduce `write_reg` and `LocatedRegister`
      sample: rust: pci: use `register!` macro
      [FOR REFERENCE] gpu: nova-core: use the kernel `register!` macro

 drivers/gpu/nova-core/falcon.rs                    |  333 +++---
 drivers/gpu/nova-core/falcon/gsp.rs                |   25 +-
 drivers/gpu/nova-core/falcon/hal/ga102.rs          |   70 +-
 drivers/gpu/nova-core/falcon/hal/tu102.rs          |   12 +-
 drivers/gpu/nova-core/falcon/sec2.rs               |   17 +-
 drivers/gpu/nova-core/fb.rs                        |    6 +-
 drivers/gpu/nova-core/fb/hal/ga100.rs              |   37 +-
 drivers/gpu/nova-core/fb/hal/ga102.rs              |    7 +-
 drivers/gpu/nova-core/fb/hal/tu102.rs              |   17 +-
 drivers/gpu/nova-core/firmware/fwsec/bootloader.rs |   19 +-
 drivers/gpu/nova-core/gfw.rs                       |   11 +-
 drivers/gpu/nova-core/gpu.rs                       |   36 +-
 drivers/gpu/nova-core/gsp/boot.rs                  |   11 +-
 drivers/gpu/nova-core/gsp/cmdq.rs                  |    9 +-
 drivers/gpu/nova-core/regs.rs                      |  616 +++++-----
 drivers/gpu/nova-core/regs/macros.rs               |  739 ------------
 rust/kernel/io.rs                                  |  411 ++++++-
 rust/kernel/io/register.rs                         | 1258 ++++++++++++++++++++
 rust/kernel/lib.rs                                 |    3 +
 rust/kernel/num/bounded.rs                         |   70 +-
 samples/rust/rust_driver_pci.rs                    |   84 +-
 scripts/Makefile.build                             |    3 +-
 22 files changed, 2416 insertions(+), 1378 deletions(-)
---
base-commit: a985880eb0f73b0d497d30dcce73e537f787b6c0
change-id: 20260117-register-ccaba1d21713

Best regards,
-- 
Alexandre Courbot <acourbot@nvidia.com>