[PATCH RESEND v4 0/4] rust: pci: add config space read/write support

[Zhi Wang <zhiw@nvidia.com>]

In the NVIDIA vGPU RFC [1], the PCI configuration space access is
required in nova-core for preparing gspVFInfo when vGPU support is
enabled. This series is the following up of the discussion with Danilo
for how to introduce support of PCI configuration space access in Rust
PCI abstractions.

v4:

- Refactor the SIZE constant to be an associated constant. (Alice)
- Remove the default method implementations in the Io trait. (Alice)
- Make cfg_size() private. (Danilo/Bjorn)
- Implement the infallible accessors of ConfigSpace. (Danilo)
- Create a new Io64 trait specifically for 64-bit accessors. (Danilo)
- Provide two separate methods for driver: config_space() and
  config_space_extended(). (Danilo)
- Update the sample driver to test the infallible accessors. (Danilo)

v3:

- Turn offset_valid() into a private function of kernel::io:Io. (Alex)
- Separate try and non-try variants. (Danilo)
- Move all the {try_}{read,write}{8,16,32,64} accessors to the I/O trait.
  (Danilo)
- Replace the hardcoded MMIO type constraint with a generic trait bound
  so that register! macro can be used in other places. (Danilo)
- Fix doctest. (John)
- Add an enum for PCI configuration space size. (Danilo)
- Refine the patch comments. (Bjorn)

v2:

- Factor out common trait as 'Io' and keep the rest routines in original
  'Io' as 'Mmio'. (Danilo)
- Rename 'IoRaw' to 'MmioRaw'. Update the bus MMIO implementation to use
  'MmioRaw'.
- Introduce pci::Device<Bound>::config_space(). (Danilo)
- Implement both infallible and fallible read/write routines, the device
  driver decicdes which version should be used.

This ideas of this series are:

- Factor out a common trait IoRegion for other accessors to share the
  same compiling/runtime check like before.

- Factor the MMIO read/write macros from the define_read! and
  define_write! macros. Thus, define_{read, write}! can be used in other
  backend.

  In detail:

  * Introduce `call_mmio_read!` and `call_mmio_write!` helper macros
    to encapsulate the unsafe FFI calls.
  * Update `define_read!` and `define_write!` macros to delegate to
    the call macros.
  * Export `define_read` and `define_write` so they can be reused
    for other I/O backends (e.g. PCI config space).

- Add a helper to query configuration space size. This is mostly for
  runtime check.

- Implement the PCI configuration space access backend in PCI
  Abstractions.

- Add tests for config space routines in rust PCI sample driver.

[1] https://lore.kernel.org/all/20250903221111.3866249-1-zhiw@nvidia.com/

Zhi Wang (4):
  rust: io: factor common I/O helpers into Io trait
  rust: io: factor out MMIO read/write macros
  rust: pci: add config space read/write support
  sample: rust: pci: add tests for config space routines

 drivers/gpu/nova-core/regs/macros.rs |  90 ++++----
 drivers/gpu/nova-core/vbios.rs       |   1 +
 rust/kernel/devres.rs                |  12 +-
 rust/kernel/io.rs                    | 298 ++++++++++++++++++++-------
 rust/kernel/io/mem.rs                |  16 +-
 rust/kernel/io/poll.rs               |   4 +-
 rust/kernel/pci.rs                   | 156 +++++++++++++-
 samples/rust/rust_driver_pci.rs      |  48 ++++-
 8 files changed, 483 insertions(+), 142 deletions(-)

-- 
2.51.0