[PATCH v4 00/16] rust: io: support register projections and remove relative registers

[Gary Guo <gary@garyguo.net>]

Currently registers work for all untyped I/O regions, which is not ideal.
It allows registers defined for device A to work for another device B and
there is no safeguarding at all.

Change this by requiring a base type for registers. `register!` can still
define registers on untyped `Region`s, although users would need to do so
explicitly and supply a concrete type.

This change makes it possible to use projection for relative registers;
relative registers can be implemented by defining new types for the I/O
subregions and just define registers for these subregion types like normal
registers.

This actually results in more ergnomic code for users of relative registers
(currently only nova-core), because non-array registers can be written to
with

    #[...]
    struct Subregion(...);

    register! {
        base: MyBase;
        SUBREGION: Subregion @ ...;
    }

    register! {
        base: Subregion;
        REG(u32) @ .. { .. }
    }

    let subregion = io_project!(bar, build: SUBREGION);
    subregion.read(REG)
    subregion.write_reg(reg)

instead of

    struct SubregionType;
    struct Subregion;
    impl RegisterBase<SubregionType> for Subregion {
        const BASE: usize = ...;
    }

    register! {
        REG(u32) @ Subregion + .. { .. }
    }

    bar.read(REG::of::<Subregion>())
    bar.write(WithBase::of::<Subregion>(), reg)

This also allows a lot more code sharing between I/O projection and
`register!` macro.

The expressiveness power of Rust declarative macros is becoming limiting,
so it is converted to a proc macro before new features being added to it.

Signed-off-by: Gary Guo <gary@garyguo.net>
---
Changes in v4:
- Rebase on 7.3-rc1.
- Many typo fixes. (Alex)
- Tweaks to `transmute` and `AsRepr`. See changelogs inline in patches.
- Link to v3: https://patch.msgid.link/20260819-typed_register-v3-0-3699a75fadf1@garyguo.net

Changes in v3:
- Convert the `register!` macro to syn.
- Add check to ensure register and alias share the same base. (Alex)
- Split transmute functionalities to `kernel::mem`. (Alex)
- Remove some stray trait bound in nova code. (Alex)
- Link to v2: https://patch.msgid.link/20260805-typed_register-v2-0-c3ca142220a0@garyguo.net

Changes in v2:
- Extract type conversion from `register!` to `Io`
- Redesign the API to be centered around regsiter projections.
  * Support register projections in `io_project!`
  * Support adding register definition without defining bitfield
  * Subregions is thus unified with other registers.
- Store projected subregions in `Falcon` for nova.
- Link to v1: https://patch.msgid.link/20260721-typed_register-v1-0-452d72b60262@garyguo.net

---
Gary Guo (16):
      rust: io: register: reimplement as proc macro
      rust: mem: add `transmute` with deferred size check
      rust: mem: add `AsRepr` and `AsReprMut`
      rust: io: perform conversions using `AsRepr`
      rust: io: support register projections
      rust: io: register: allow explicit base type specification
      gpu: nova-core: specify base type for registers
      drm/tyr: specify base type for registers
      samples: rust: pci: specify base type for registers
      rust: io: register: make register have a typed base
      rust: io: register: support fixed offset register without bitfield
      gpu: nova-core: use projection for PFALCON and PFALCON2 registers
      gpu: nova-core: convert hshub0 from relative register to projection
      rust: io: register: remove relative registers
      rust: io: register: remove `Register` trait and cleanup macro
      rust: io: register: unify handling of register with/without bitfields

 MAINTAINERS                                        |   1 +
 drivers/gpu/drm/tyr/driver.rs                      |   1 +
 drivers/gpu/drm/tyr/fw.rs                          |   5 +-
 drivers/gpu/drm/tyr/regs.rs                        |  45 +-
 drivers/gpu/nova-core/driver.rs                    |   1 +
 drivers/gpu/nova-core/falcon.rs                    | 161 ++---
 drivers/gpu/nova-core/falcon/fsp.rs                |  63 +-
 drivers/gpu/nova-core/falcon/gsp.rs                |  51 +-
 drivers/gpu/nova-core/falcon/hal/ga102.rs          |  59 +-
 drivers/gpu/nova-core/falcon/hal/tu102.rs          |   9 +-
 drivers/gpu/nova-core/falcon/sec2.rs               |  37 +-
 drivers/gpu/nova-core/fb/hal/gb100.rs              |  59 +-
 drivers/gpu/nova-core/fb/regs.rs                   |  31 +-
 drivers/gpu/nova-core/firmware/fwsec/bootloader.rs |  18 +-
 drivers/gpu/nova-core/gsp/hal/tu102.rs             |   7 +-
 drivers/gpu/nova-core/gsp/regs.rs                  |   9 +-
 drivers/gpu/nova-core/regs.rs                      | 115 ++--
 drivers/gpu/nova-core/vbios.rs                     |  11 +-
 rust/kernel/bitfield.rs                            |   9 +
 rust/kernel/device_id.rs                           |   3 +-
 rust/kernel/io.rs                                  | 181 +++--
 rust/kernel/io/register.rs                         | 759 +++++----------------
 rust/kernel/lib.rs                                 |   1 +
 rust/kernel/mem.rs                                 | 231 +++++++
 rust/kernel/sync/atomic.rs                         |   4 +-
 rust/macros/io/mod.rs                              |   3 +
 rust/macros/io/register.rs                         | 296 ++++++++
 rust/macros/lib.rs                                 |   9 +
 samples/rust/rust_driver_pci.rs                    |   4 +
 29 files changed, 1230 insertions(+), 953 deletions(-)
---
base-commit: cee9395acd8043be0644b25c34bfa86623f2b935
change-id: 20260721-typed_register-176eab3abee7

Best regards,
--  
Gary Guo <gary@garyguo.net>