This patch series implements the groundwork for using io-uring cmd
interface in rust miscdevice.

 1. Io-uring headers for bindings
    We needs additional headers for implementing rust abstraction.

 2. zero-init pdu in io_uring_cmd
    We need to initialize pdu for avoiding UB when reading pdu in rust.

 3. Core abstractions
    Provides 2 core struct for abstraction. One is for io_uring_cmd and
    another is for io_uring_sqe.

 4. Method for MiscDevice
    MiscDevice has some method for `file_operations`. This patch adds a
    method `uring_cmd` which could be used in miscdevice driver.

 5. uring_cmd interface for MiscDevice sample
    Added sample code for using new interface for `MiscDevice::uring_cmd()`

Together, these 5 patches.

 - io-uring headers for bindings
 - zero-init pdu in io_uring_cmd
 - abstraction types for io-uring interface
 - add uring_cmd method for miscdevice
 - sample that implements uring_cmd method

Changelog:
v2:
* use pinned &mut for IoUringCmd
* add missing safety comments
* use write_volatile for read uring_cmd in sample

v3:
* fixes various comments including safety related ones.
* zero-init pdu in io_uring_cmd
* use `read_pdu`/`write_pdu` with `AsBytes`/`FromBytes` for pdu
* `IoUringSqe::cmd_data` checkes opcode and returns `FromBytes`
* use `_IOR`/`_IOW` macros for cmd_op in sample

Sidong Yang (5):
  rust: bindings: add io_uring headers in bindings_helper.h
  io_uring/cmd: zero-init pdu in io_uring_cmd_prep() to avoid UB
  rust: io_uring: introduce rust abstraction for io-uring cmd
  rust: miscdevice: Add `uring_cmd` support
  samples: rust: Add `uring_cmd` example to `rust_misc_device`

 io_uring/uring_cmd.c             |   1 +
 rust/bindings/bindings_helper.h  |   2 +
 rust/kernel/io_uring.rs          | 306 +++++++++++++++++++++++++++++++
 rust/kernel/lib.rs               |   1 +
 rust/kernel/miscdevice.rs        |  53 +++++-
 samples/rust/rust_misc_device.rs |  27 +++
 6 files changed, 389 insertions(+), 1 deletion(-)
 create mode 100644 rust/kernel/io_uring.rs

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2.43.0