currently the rust `Io` type maps to the c read{b, w, l, q}/write{b, w, l, q}
functions and have no support for port io. this can be a problem for pci::Bar
because the pointer returned by pci_iomap can be either PIO or MMIO [0].

this patch series splits the `Io` type into `Io`, and `MMIo`. `Io` can be
used to access PIO or MMIO. `MMIo` can only access memory mapped IO but
might, depending on the arch, be faster than `Io`. and updates pci::Bar,
so that it is generic over Io and, a user can optionally give a compile
time hint about the type of io. 

Link: https://docs.kernel.org/6.11/driver-api/pci/pci.html#c.pci_iomap [0]

changes in v2:
  - remove `PortIo`
  - typo fixes
  - squash "fixup" patches so that patches will not introduce build fails
  - move some changes across patches so that build will not fail
  - changes macro define in rust/helpers/io.c to use full rust name
  - specialize `io_backend` for the x86 case
  - do not modify lib/iomap.c
  - rebased on v6.15-rc6

Link to v1: https://lore.kernel.org/rust-for-linux/20250509031524.2604087-1-andrewjballance@gmail.com/  

Andrew Ballance (3):
  rust: io: add new Io type
  rust: io: add from_raw_cookie functions
  rust: pci: make Bar generic over Io

Fiona Behrens (3):
  rust: helpers: io: use macro to generate io accessor functions
  rust: io: make Io use IoAccess trait
  rust: io: implement Debug for IoRaw and add some doctests

 drivers/gpu/nova-core/driver.rs |   4 +-
 drivers/gpu/nova-core/regs.rs   |   1 +
 rust/helpers/io.c               | 112 ++----
 rust/kernel/devres.rs           |   4 +-
 rust/kernel/io.rs               | 645 +++++++++++++++++++++++---------
 rust/kernel/pci.rs              | 101 +++--
 samples/rust/rust_driver_pci.rs |   6 +-
 7 files changed, 595 insertions(+), 278 deletions(-)


base-commit: 82f2b0b97b36ee3fcddf0f0780a9a0825d52fec3
-- 
2.49.0

On Wed, May 14, 2025 at 12:58 PM Andrew Ballance
<andrewjballance@gmail.com> wrote:
>
> currently the rust `Io` type maps to the c read{b, w, l, q}/write{b, w, l, q}
> functions and have no support for port io. this can be a problem for pci::Bar
> because the pointer returned by pci_iomap can be either PIO or MMIO [0].
>
> this patch series splits the `Io` type into `Io`, and `MMIo`. `Io` can be
> used to access PIO or MMIO. `MMIo` can only access memory mapped IO but
> might, depending on the arch, be faster than `Io`. and updates pci::Bar,
> so that it is generic over Io and, a user can optionally give a compile
> time hint about the type of io.
>
> Link: https://docs.kernel.org/6.11/driver-api/pci/pci.html#c.pci_iomap [0]

This series seems to try and solve parts of the same problems as
Daniel's patchset:
https://lore.kernel.org/rust-for-linux/20250603-topics-tyr-platform_iomem-v9-0-a27e04157e3e@collabora.com/#r

We should probably align these two patchsets so that they do not add
incompatible abstractions for the same thing.

Alice

On 6/16/25 10:03 AM, Alice Ryhl wrote:
> On Wed, May 14, 2025 at 12:58 PM Andrew Ballance
> <andrewjballance@gmail.com> wrote:
>>
>> currently the rust `Io` type maps to the c read{b, w, l, q}/write{b, w, l, q}
>> functions and have no support for port io. this can be a problem for pci::Bar
>> because the pointer returned by pci_iomap can be either PIO or MMIO [0].
>>
>> this patch series splits the `Io` type into `Io`, and `MMIo`. `Io` can be
>> used to access PIO or MMIO. `MMIo` can only access memory mapped IO but
>> might, depending on the arch, be faster than `Io`. and updates pci::Bar,
>> so that it is generic over Io and, a user can optionally give a compile
>> time hint about the type of io.
>>
>> Link: https://docs.kernel.org/6.11/driver-api/pci/pci.html#c.pci_iomap [0]
> 
> This series seems to try and solve parts of the same problems as
> Daniel's patchset:
> https://lore.kernel.org/rust-for-linux/20250603-topics-tyr-platform_iomem-v9-0-a27e04157e3e@collabora.com/#r
> 
> We should probably align these two patchsets so that they do not add
> incompatible abstractions for the same thing.

AFAICS, they solve different problems, i.e.

   1) Add Port I/O support to the generic I/O abstractions.
   2) Add an abstraction for generic ioremap() used to map a struct resource
      obtained from a platform device.

The patch series will conflict though, I think it would be best to rebase this
one onto Daniel's patch series, since it is close to land.