[PATCH v2 0/2] rust: Add uapi crate

[Asahi Lina]

In general, direct bindgen bindings for C kernel APIs are not intended
to be used by drivers outside of the `kernel` crate. However, some
drivers do need to interact directly with UAPI definitions to implement
userspace APIs.

Instead of making this an exception to the use of the `bindings` crate,
introduce a new `uapi` crate that will contain only these publicly
usable definitions. The build logic mirrors the `bindings` crate, but
there is no helper support since UAPIs are only intended to contain
constant and type definitions, not function prototypes.

In the future, we would like to extend this to also auto-derive and
validate certain safety properties for UAPI structure definitions, such
as that they are safely castable to/from "bag of bits" buffers.

The first patch introduces the `uapi` crate proper and stands on its own,
while the second patch introduces the `ioctl` module in the kernel crate
that uses it.

(Miguel: this series should apply stand-alone now)

Signed-off-by: Asahi Lina <lina@xxxxxxxxxxxxx>
---
Changes in v2:
- Fixed the trailing '\' warning (mirroring the fix from Vicenzo
  Palazzo)
- Pulled in the ioctl module patch into this series. Per the discussion
  in the meeting, this could be moved into the uapi crate in principle,
  but we can decide to do that later since the whole buildsystem is
  likely to undergo major changes anyway.
- Link to v1: https://lore.kernel.org/r/20230329-rust-uapi-v1-0-ee78f2933726@xxxxxxxxxxxxx

---
Asahi Lina (2):
      rust: uapi: Add UAPI crate
      rust: ioctl: Add ioctl number manipulation functions
 rust/.gitignore         |  1 +
 rust/Makefile           | 18 +++++++++++--
 rust/kernel/ioctl.rs    | 71 +++++++++++++++++++++++++++++++++++++++++++++++++
 rust/kernel/lib.rs      |  2 ++
 rust/uapi/lib.rs        | 27 +++++++++++++++++++
 rust/uapi/uapi_helper.h |  9 +++++++
 6 files changed, 126 insertions(+), 2 deletions(-)
---
base-commit: fe15c26ee26efa11741a7b632e9f23b01aca4cc6
change-id: 20230329-rust-uapi-894421e9a5d2

Thank you,
~~ Lina